Author Topic: Live on CrowdSupply! muArt - A UART converter finally done right  (Read 9841 times)

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Offline pylo

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The campaign is live!
Visit the muArt campaign page and pledge now to receive your device among the first people.

UPDATE 5: Manufactured electronics arrived and work perfectly. Details in post #63. Also updated text below for current status.
UPDATE 4: Prototype cases arrived. They are great, details in post #58.
UPDATE 3: Added photorealistic render of planned plastic case. See post #42 for more details.
UPDATE 2: Added schematics as promised.
UPDATE 1: The forum replaced all my Greek "mu" with "?". I am now correcting it, remember wherever you see "muArt", "mu" is for the greek letter.

Okay, I know what you think - “Another one?!” - But in my experience, available UART converters, even the isolated better ones, still do not cater for all needs, at least surely not for mine, so I set out to make my own device. Let me introduce you to the muArt (“myuArt” - as a wordplay on both micro and UART).

My goals were to make the muArt safe, reliable, universal, and comfortable. Obviously these needs arise from experiences I've lived through. Let me elaborate on these points:

Safe
Accidents happen, especially during development, experimentation and debugging. Cables can be connected the wrong way, polarities reversed, two drivers interconnected, wrong voltages selected, or simply just a faulty component or a mistake in a design. These often mean the end of your computer’s USB port… or the converter’s… or your creation’s… or yours. I want my ideal UART converter to be safe for other devices and the user, even in the face of hardware faults or user mistakes like mixed up wires. Oh, and since it is sitting on my bench and sometimes (*cough*) with pieces of metal, solder and other boards laying around, I’d appreciate if it didn’t cause any shorts itself. To support this goal, the muArt has:
  • Complete galvanic isolation, even for mains-level and higher voltages. Electric currents cannot flow between your computer and the other board. This spells safety for you and your computer, while also helping to keep noise levels down.
  • Reverse polarity protection. The converter will survive even if you mix up the power pins.
  • Over-current protection on all peripheral IO pins. With the muArt it is not a problem if you wire it up wrong by mistake. Both the converter’s and your other board’s pins will survive.
  • A professional custom-designed case to prevent damage, shorts, and other troubles. Use, grip, handle, and transport the muArt with ease and without worries.

Reliable
A UART converter is one of my tools, and I should definitely not be debugging it instead of my creation. I want my tools to be reliable. I hate that minute while I’m trying to figure out why I get no data, just to find out that something (probably?) latched up and only needed a power cycle. It is frustrating when my terminal gets garbled up due to floating inputs upon device (dis)connection. And it is far from funny when my last converter turns out to be broken - either due to my own mistakes (see list above) or just plain who-knows-why. Did I mention USB protocol disconnections due to other devices on the bus doing their thing? To support this goal, the muArt has:
  • Pullups on all inputs, so that disconnected pins don’t cause funny things like garbage random input, a ruined terminal app, or corrupt application state.
  • Judicious filtering. Each IC in the converter is decoupled using multiple capacitors, both locally and in bulk. The USB signals and power are filtered, and sensitive pins are protected with RC networks.
  • Complete ESD protection for all external pins. ESD damage is tricky because things can seem to work for a while after an ESD event, and you don’t need visible sparks to have them.

Universal
My ideal converter should give me everything I need for basic communication (obviously), also for handshaking, and importantly for flashing other boards. It should support all relevant voltages, notably 1.8V, which aside from working with very-low power devices, is a must-have for FPGA designers. The converter must also lend itself to low-noise circuits, enabling communication with sensitive analog systems without disrupting them. To support this goal, the muArt has:
  • RXD, TXD, DTR, RTS, and CTS. Usable for flashing various ESP32 boards and multiple Arduinos such as the Nanos and Pro Minis. Hardware handshaking allows for reliable high-speed UART.
  • A wide working voltage of 1.8 to 5.4V. Yes, also usable for FPGAs. Coupled with the galvanic isolation, you basically get “voltage auto-sensing”, meaning the converter will automatically use the correct voltage levels for UART communication. No more setting jumpers or “Which of these 5 converter boards was the one for 3V3?”. One converter to use everywhere.
  • Suitability for communicating with low-noise circuits, supported by the filters, the isolation, and careful layout.

Comfortable
Readable labels on pins never hurt (sarcasm). LEDs should let me know when there is activity. Since UART communication is probably the first thing you try on board bringup, some extra feedback or GPIOs can be extremely practical. Mechanically, I want to be able to actually grab the thing without making shorts all over the place and without making my jumper wires come loose. To support this goal, the muArt has:
  • A general-purpose in and a general-purpose out pin that you can control directly over USB, parallel to the UART lines.
  • Four LEDs, each of different color to make them immediately distinguishable. One lights up if power is connected, two indicate RX/TX activity, while the last one is connected to the general-purpose in, giving you visual feedback about its state without special software on the host computer.
  • Four-wall shrouded header. Gives protection from shorts by tipped board or dangling wires. Also gives a nice firm surface to grip the converter by, again without the risk of shorts or ESD damage from your fingers.
  • Readable descriptions printed on the PCB to help you remember the most important things about usage.

Wow, this turned out lengthy, sorry about that. So, where am I with the project? The design and layout is done and manufactured prototypes have arrived, they have been tested, and every feature works as it should. Now I would like to crowdfund a batch if there is enough interest. I’m trying to get about 200 pre-orders, because that amount would suffice to make the price just barely reasonable (estimated crowdfunding price is around 30$). Preparations for the campaign are ongoing so the campaign is not online yet, but I will let everybody know once it is.

Do you like the muArt? Would you buy one / would you support the crowdfunding campaign ? I'd be happy to see your feedback :)
« Last Edit: August 09, 2018, 08:56:24 am by pylo »
 

Online ataradov

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Re: myuArt - A UART converter finally done right
« Reply #1 on: April 19, 2018, 06:00:55 am »
I'm not sure what you are doing with UART that is so hardcore, but 3.3V FTDI cable covers all my requirements.  And it is very compact and reliable enough.

I would like to see some design files before I commit to something with so many promises.
Alex
 
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Offline os40la

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Re: myuArt - A UART converter finally done right
« Reply #2 on: April 19, 2018, 06:08:52 am »
Sounds Interesting. I have been looking around for something like this for a reasonable price. What speed would we be looking at?. From my research galvanic isolation seems to limit the speed.
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Offline Mr.B

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Re: myuArt - A UART converter finally done right
« Reply #3 on: April 19, 2018, 06:20:40 am »
I would like to see some design files before I commit to something with so many promises.

Me too.
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Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #4 on: April 19, 2018, 06:46:12 am »
I'm not sure what you are doing with UART that is so hardcore, but 3.3V FTDI cable covers all my requirements.
The muArt is not about industrial or any "hardcore" usage. It is just one board that is universal enough to be used everywhere while giving you some comfort and handy features. I think the FTDI cable you mention is a very good example to support my campaign, actually. It might be robust enough, but each cable only supports a single voltage, and each cost about 22$. That is near the price for my board, but from FTDI you might need 3 of those cables (different voltages for different projects), so you've already spent over 65$, and you still don't get all the handy stuff from the muArt, like the DTR pin (needed for flashing ESP32 boards), the GPIOs, LED activity feedback etc. If your hardware projects are different enough, you will have 3-5 different converters in the end and have paid 70$, whereas you could just have bought a muArt. That is what this project is about, not about being hardcore. EDIT: The safety and robustness features are mostly just protection against common user mistakes that most other boards do not provide.

Alternatively, you can go to Amazon or eBay and buy those 2-5$ chinese import boards, but those are not nearly as robust as the FTDI cables, and otherwise lack the same features.

I will publish schematics, at latest sometime during prototype manufacturing, possibly earlier. There is nothing magic about the board that, just simple stuff that anybody could do. I think it is just that most converter boards try to be as cheap as possible, while I prefer to be higher quality even if costs a bit.
« Last Edit: April 19, 2018, 07:21:16 am by pylo »
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #5 on: April 19, 2018, 06:50:39 am »
Sounds Interesting. I have been looking around for something like this for a reasonable price. What speed would we be looking at?. From my research galvanic isolation seems to limit the speed.

Correct, optocouplers tend to be the limiting factor when it comes to speed. That is why the muArt uses magnetic coupling, and theoretically it should achieve 3Mbaud/s (supported by both the USB bridge and the isolation). While I calculated the filters for 3Mbaud, those could also limit speed if I made a mistake. So my intention is 3Mbaud, but let me test my prototypes first before making any promises about this.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #6 on: April 19, 2018, 07:03:21 am »
By the way, the key components are the CP2102N and the MAX14932. The latter will be replaced ofc should the 3Mbaud speed turn out to be unachievable.
 

Offline spanner888

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Re: myuArt - A UART converter finally done right
« Reply #7 on: April 19, 2018, 03:57:08 pm »
The auto voltage sensing has got me especially interested.

Other features also sound great.

I have heaps of cheap ones already, but will definitely pay that sort of $A.
 

Offline janekm

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Re: myuArt - A UART converter finally done right
« Reply #8 on: April 19, 2018, 04:18:25 pm »
Personally I avoid FTDI like the plague after their driver debacle (and their obnoxious distribution policy), so I'm glad you went for CP2101  ;D

Lately I've started to just place the Holtek HT42B534 USB-UART chip on my boards since it is literally the cost of 5 pringles chips and works well, this way I can get users in the field to read out diagnostics without having to ensure they have a separate cable / module.

It's fairly rare for me to need an isolated USB-serial adapter (though there's been one case) so I might hesitate to pitch in... I suspect this project may turn out to be a little niche (but maybe 250 orders is realistic). Good luck anyway, I'll be glad to see this exist in case I need it in the future  :D
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #9 on: April 19, 2018, 05:31:12 pm »
The HT42B534 is new to me. Looks interesting, the IC has good features and is priced very aggressively. But I cannot find a reliable distribution channel (actually the only place I've found it was alibaba), and also no information about a working driver for Linux. If the latter does not exist, that'd be a big and serious no-go for me.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #10 on: April 19, 2018, 06:15:22 pm »
I added a render to top post. Physical board size is less than 53 x 24mm. Real-life images follow once I get the prototypes.
 

Offline Cerebus

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Re: myuArt - A UART converter finally done right
« Reply #11 on: April 19, 2018, 07:07:36 pm »
... and also no information about a working driver for Linux. If the latter does not exist, that'd be a big and serious no-go for me.

It shouldn't need one. Quoting from the landing page for the device from Holtek's website: "Communication Device Class (CDC) for communications and configuration". CDC class drivers are completely generic (by design) and I can't think of a major operating systems that doesn't natively support the CDC profile for a basic serial port straight out of the box. I'd want to test it before relying on that, because you can't be sure that they have implemented the standard properly, but if they have it should "just workTM".
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Offline janekm

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Re: myuArt - A UART converter finally done right
« Reply #12 on: April 20, 2018, 07:14:54 pm »
... and also no information about a working driver for Linux. If the latter does not exist, that'd be a big and serious no-go for me.

It shouldn't need one. Quoting from the landing page for the device from Holtek's website: "Communication Device Class (CDC) for communications and configuration". CDC class drivers are completely generic (by design) and I can't think of a major operating systems that doesn't natively support the CDC profile for a basic serial port straight out of the box. I'd want to test it before relying on that, because you can't be sure that they have implemented the standard properly, but if they have it should "just workTM".

Indeed, that's why I like it. At least on relatively recent versions of MacOS and Windows 10 it just works without any driver install needed (older versions of Windows need a .INF file to tell it that yes, it can go ahead and use the default CDC driver). I would not expect any issues at all under Linux either, though I haven't had a reason to test that yet.

A quirk of using the CDC class is that it will be considered a USB modem by the OS, but I don't think there are any practical downsides to that. It's possible to write to the chip to overwrite the default name it comes with.

In terms of distribution, it's true that Holtek don't have much "western" distribution (their chips mostly go into low-cost consumer goods, for example Dave is using a Holtek LCD driver chip in his latest project), but you may be able to get the chips directly from Holtek, or they should be able to tell you who their local distributor is. But they're a long established Taiwanese company so not a fly-by-night outfit likely to disappear any time soon (and in fact they have very little volatility in their offering, they don't sunset products very often from what I've seen).
 

Online BNElecEng

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Re: myuArt - A UART converter finally done right
« Reply #13 on: April 20, 2018, 07:22:31 pm »
Hi pylo. I'd be interested in a couple of your boards. Please let us know how your prototypes turn out and when the crowd sourcing campaign starts.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #14 on: April 21, 2018, 08:11:23 pm »
@BNElecEng: Thank you, sure, I will let everybody know.

@Everybody: Please do let me know if you are interested. You need not promise anything, I'd just like to know if you think such a board could be interesting. Critique is also welcome, that is the whole point of asking for feedback.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #15 on: April 21, 2018, 08:15:11 pm »
@ataradov: As promised, I've attached schematics to the first post.
 

Online ogden

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Re: myuArt - A UART converter finally done right
« Reply #16 on: April 21, 2018, 08:39:45 pm »
@Everybody: Please do let me know if you are interested.

Thank you, I am fine with non-isolated converters I have. Also I do not agree to "done right". Mine generic non-isolated converters have better insulation than yours. Why? - They are inside heat shrink tubes. Due to offset USB connector and UART connector which is not edge-mount, your board is not compatible with heatshrink tubing.
« Last Edit: September 14, 2018, 03:19:42 am by ogden »
 

Offline T3sl4co1l

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Re: myuArt - A UART converter finally done right
« Reply #17 on: April 21, 2018, 08:45:54 pm »
Le sigh, USB still being used badly.  >:(

Just tie shield and GND directly to GND.  Only bad things happen by introducing impedance.  Shield in particular should be tied to circuit ground plane as soon as possible, and in as many places as possible.

There are a few use cases where enclosure ground should be used to handle ESD, with a little isolation between that and internal ground, but such is the domain of experts.  It's definitely not the way to handle a dongle, which is its own ground period.

(And yes, I wish I could address this towards whatever appnotes you read that promoted these exactly wrong ideas.  Pass it on, if you will.)

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Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #18 on: April 21, 2018, 08:56:25 pm »
Mine generic non-insolated converters have better isolation than yours. Why? - They are inside heat shrink tubes. Due to offset USB connector and UART connector which is not edge-mount, your board is not compatible with heatshrink tubing.
Mind you, we are talking about two different cases of isolation. The heatshrink tubing you refer to does not actually solve any of the problems the galvanic isolation in the muArt does. Galvanic isolation prevents dangerous voltages or high currents from reaching your host computer and isolates noise, a heatshrink does not do these. What the heatshrink does, it prevents damage (by ESD or shorts) to the uart-converter itself. Galvanic isolation protects not the converter, but you and everyhing else.

That said, I was already thinking about adding heatshrink tubing too (not instead), and I'm not sure the offset USB receptacle would prevent it. However, it is surely no problem to modify the board layout to make it centered. Maybe I'll do a quick layout revision just to be sure. Thank you for pointing this out.
« Last Edit: April 21, 2018, 09:02:16 pm by pylo »
 

Offline Cerebus

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Re: myuArt - A UART converter finally done right
« Reply #19 on: April 21, 2018, 09:02:14 pm »
@Everybody: Please do let me know if you are interested.

Thank you, I am fine with non-isolated converters I have. Also I do not agree to "done right". Mine generic non-insolated converters have better isolation than yours. Why? - They are inside heat shrink tubes. Due to offset USB connector and UART connector which is not edge-mount, your board is not compatible with heatshrink tubing.

I think you're confusing insulation with [galvanic] isolation - the two are not the same thing.

Oh, and the heatshrink thing - what?. I hardly think that someone not explicitly designing their product to suit bodger's methods is a problem.
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Online ogden

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Re: myuArt - A UART converter finally done right
« Reply #20 on: April 21, 2018, 09:40:40 pm »
I think you're confusing insulation with [galvanic] isolation - the two are not the same thing.

Oh, really? - Thank you for clarifying  :-DD

I meant insulation indeed. Funny that my native language (which more or less obviously is not Englisch) does not have separate words for isolation/insulation.

Quote
Oh, and the heatshrink thing - what?. I hardly think that someone not explicitly designing their product to suit bodger's methods is a problem.

You may work using bare wires and bare PCB's of your tools all over your desk - I don't mind. Personally I want my tools to be insulated. If you think your product will be used only by beginners which will never work with/on expensive equipment, then indeed make that adapter as inconvenient as possible.
 

Online Monkeh

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Re: myuArt - A UART converter finally done right
« Reply #21 on: April 21, 2018, 09:44:28 pm »
So put a 3D printed case on the thing. Wrapping stuff in heatshrink fairly sucks.
 

Online ogden

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Re: myuArt - A UART converter finally done right
« Reply #22 on: April 21, 2018, 10:00:11 pm »
So put a 3D printed case on the thing.

So I have to buy 3d printer to get that thing into case? - No, thanx :)
Actually 3D-printed enclosure would benefit from edge-mount connector as well.

Quote
Wrapping stuff in heatshrink fairly sucks.

Visually maybe, thou translucent does not look that bad:

https://www.tindie.com/products/Saimon/debug-board-usb-to-uart-with-voltage-translator/
« Last Edit: April 22, 2018, 12:56:26 am by ogden »
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #23 on: April 21, 2018, 10:36:24 pm »
Le sigh, USB still being used badly.  >:(

Just tie shield and GND directly to GND.  Only bad things happen by introducing impedance.  Shield in particular should be tied to circuit ground plane as soon as possible, and in as many places as possible.

There are a few use cases where enclosure ground should be used to handle ESD, with a little isolation between that and internal ground, but such is the domain of experts.  It's definitely not the way to handle a dongle, which is its own ground period.

(And yes, I wish I could address this towards whatever appnotes you read that promoted these exactly wrong ideas.  Pass it on, if you will.)

Tim

Well, it's not just about an appnote. There are plenty examples (forum posts, schematics, appnotes) advocating the way I did it too. Certainly the most common two schools are 1) on peripheral side connect the shield directly to ground (like you said), and 2) through some network (like I did). Frankly I don't have the resources to do actual EMI testing - on that note, if anybody can help me with that even if non-officially I'd be glad to send a few boards - but based on my research this is not so bad. Maybe one can argue if it could be better, but by leaving the schematics like this, I can always switch to your solution by not placing the cap and replacing the resistor with a 0-ohm. So this is certainly the most versatile. FYI, I made sure to connect shield to ground at a quite area of the board.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #24 on: April 21, 2018, 10:55:26 pm »
On the topic of a case: yeah best would be to have one too, but the options are:
  • Let a case of my own be manufactured. Too expensive below 10.000pcs, so not an option.
  • Design into an existing case. This would still need to be modified with cutouts for cables and windows for LEDs plus printing for labels. Also, the board is pretty small, so a standard case would make it a lot bulkier (and uglier).
  • Design and 3D-print the case myself. First, I have no experience with mechanical design, and second I don't have a 3D printer.
  • Ask for help in design, and share the design so that anybody can print their own case. This is not so bad, but most people still don't have a 3D printer, so only a few would be able to benefit from this solution.
  • Apply heatshrink. Might not be "professional", but TBH it works, it is cheap, and is available for everybody. And as already pointed out, not so ugly as long as transparent.
  • Apply conformal coating to the board. I think this could be workable as far as costs are concerned (though not so sure as it would require a 2-phase assembly), however, this is far too unreliable (abresion, thickness etc.), so I call my veto on this.

Summarizing, only heatshrinking works that I can readily ship to my backers. Having a public design for a custom 3D-printed case would be ultra-cool, but people would need to print it themselves. EDIT: Or, have a backer tier during the campaign where a printed case is included, but sold at a higher price.
« Last Edit: April 21, 2018, 11:00:34 pm by pylo »
 

Offline T3sl4co1l

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Re: myuArt - A UART converter finally done right
« Reply #25 on: April 22, 2018, 12:04:04 am »
Digi-Key does value-add enclosures, FWIW.  I haven't quoted them yet but it can't be too horrible.  I'd think it's worth looking into for 100s+.

Labels are easily printed, as well.  The combination very easily looks pretty sharp:



Tim
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Offline Cerebus

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Re: myuArt - A UART converter finally done right
« Reply #26 on: April 22, 2018, 12:08:13 am »
I meant insulation indeed. Funny that my native language (which more or less obviously is not Englisch) does not have separate words for isolation/insulation.

How are we to know? Your name, Ogden, is a fine old English northern surname, you haven't set your country in your profile, and your English is considerably better than that offered up by certain native English speakers on this forum. So, no, it's not obvious that your native language isn't English. However, guessing: Verstehen Sie jetzt?
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Offline DTJ

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Re: myuArt - A UART converter finally done right
« Reply #27 on: April 22, 2018, 12:10:43 am »
Following along.
 

Offline sequoia

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Re: myuArt - A UART converter finally done right
« Reply #28 on: April 22, 2018, 07:41:36 am »
No DSR?    On adapter like this  at minimum I'd like to see both CTS/RTS and DTR/DSR pairs, and ideally all signals...
 

Offline Maxlor

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Re: myuArt - A UART converter finally done right
« Reply #29 on: April 22, 2018, 08:38:18 am »
Case wise, using a potting box with the PCB as top cover (like Dave's µCurrent) would seem like a good and cheap solution. I've used that technique myself for low count projects (5 pieces), and I was happy with how it turned out. It certainly helps to mitigate ESD stuff and improves general mechanical robustness if you can't actually touch any circuitry and only the connectors are exposed.
 

Online ogden

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Re: myuArt - A UART converter finally done right
« Reply #30 on: April 22, 2018, 11:09:01 am »
I meant insulation indeed. Funny that my native language (which more or less obviously is not Englisch) does not have separate words for isolation/insulation.

How are we to know?

Educated guess that author of the post is not so dumb to imply that heat shrink adds galvanic isolation to the USB-UART interface? What remains is typo or illiteracy :)

Case wise, using a potting box with the PCB as top cover (like Dave's µCurrent) would seem like a good and cheap solution.

Interface adapter shall be small and shall not mind top or bottom orientation. This is one reason why for stm32 playground projects I stopped to use J-Link but use cheap 3$ ST-Link knockoff instead. It takes virtually no space on the table, can be rotated as you (your device) wants. Thou said ST-link have metallic enclosure which is no good. Enclosure of interface converter shall be made completely out of insulator so you can drop it INTO live device w/o danger of shorting something and blowing-up.
 

Offline Navarro

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Re: myuArt - A UART converter finally done right
« Reply #31 on: April 22, 2018, 11:15:12 am »
I already have something like this designed: https://github.com/PY1CX/Quad-Serial

There is some things that I wanted to change in a next version but this can be an example.
PY1CX
34401A - DSOX2002A - 66332A
 
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Offline Cerebus

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Re: myuArt - A UART converter finally done right
« Reply #32 on: April 22, 2018, 11:38:24 am »
I meant insulation indeed. Funny that my native language (which more or less obviously is not Englisch) does not have separate words for isolation/insulation.

How are we to know?

Educated guess that author of the post is not so dumb to imply that heat shrink adds galvanic isolation to the USB-UART interface? What remains is typo or illiteracy :)


I meant "How are we to know [that you're not a native English speaker]?"

As to the latter, it wouldn't be the dumbest thing we've seen on here.   The rule seems to be "never underestimate human stupidity" and "never underestimate some people's total inability to actually explain what they mean". :)

Quote
Interface adapter shall be small and shall not mind top or bottom orientation. This is one reason why for stm32 playground projects I stopped to use J-Link but use cheap 3$ ST-Link knockoff instead. It takes virtually no space on the table, can be rotated as you (your device) wants. Thou said ST-link have metallic enclosure which is no good. Enclosure of interface converter shall be made completely out of insulator so you can drop it INTO live device w/o danger of shorting something and blowing-up.

I've got a bunch of those, worth more than the $2-3 they cost. They have anodised aluminium cases, and aluminium oxide is a very good insulator. I just slapped the 4 wire probes across them and my meter can't see any conductance - sticks on OL on the 200MΩ range - so I don't think there's any worries there.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online Mr. Scram

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Re: myuArt - A UART converter finally done right
« Reply #33 on: April 22, 2018, 11:49:33 am »
On the topic of a case: yeah best would be to have one too, but the options are:
  • Let a case of my own be manufactured. Too expensive below 10.000pcs, so not an option.
  • Design into an existing case. This would still need to be modified with cutouts for cables and windows for LEDs plus printing for labels. Also, the board is pretty small, so a standard case would make it a lot bulkier (and uglier).
  • Design and 3D-print the case myself. First, I have no experience with mechanical design, and second I don't have a 3D printer.
  • Ask for help in design, and share the design so that anybody can print their own case. This is not so bad, but most people still don't have a 3D printer, so only a few would be able to benefit from this solution.
  • Apply heatshrink. Might not be "professional", but TBH it works, it is cheap, and is available for everybody. And as already pointed out, not so ugly as long as transparent.
  • Apply conformal coating to the board. I think this could be workable as far as costs are concerned (though not so sure as it would require a 2-phase assembly), however, this is far too unreliable (abresion, thickness etc.), so I call my veto on this.

Summarizing, only heatshrinking works that I can readily ship to my backers. Having a public design for a custom 3D-printed case would be ultra-cool, but people would need to print it themselves. EDIT: Or, have a backer tier during the campaign where a printed case is included, but sold at a higher price.
You're applying an answer to a question. Having cases made doesn't have to be that expensive, even when numbers aren't huge. Calling conformal coating unreliable doesn't seem to coincide with practical experience.

If you want to pick a solution because you want that solution that's fine, but be honest with yourself about your reasons.
 

Offline janekm

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Re: myuArt - A UART converter finally done right
« Reply #34 on: April 22, 2018, 03:27:50 pm »
Regarding the case, there are plenty of off-the-shelf cases designed for USB interfacing devices like this.
There's the rather cute one use by the ST-Link clones: https://www.sunrom.com/p/st-link-v2 (anodised aluminium so has the potential insulation issue if it gets scratched), and they're already using the same connector as you are.
Similar plastic versions exist too. Just have a look at the many enclosures designed for USB memory sticks, some of them should suit your project.

Getting cases customised from Digikey is likely to be prohibitively expensive for a project like this.
 

Online Mr. Scram

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Re: myuArt - A UART converter finally done right
« Reply #35 on: April 22, 2018, 03:40:38 pm »
Regarding the case, there are plenty of off-the-shelf cases designed for USB interfacing devices like this.
There's the rather cute one use by the ST-Link clones: https://www.sunrom.com/p/st-link-v2 (anodised aluminium so has the potential insulation issue if it gets scratched), and they're already using the same connector as you are.
Similar plastic versions exist too. Just have a look at the many enclosures designed for USB memory sticks, some of them should suit your project.

Getting cases customised from Digikey is likely to be prohibitively expensive for a project like this.
Why insist on Digikey?
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #36 on: April 22, 2018, 07:34:42 pm »
You're applying an answer to a question. Having cases made doesn't have to be that expensive, even when numbers aren't huge. Calling conformal coating unreliable doesn't seem to coincide with practical experience.

If you want to pick a solution because you want that solution that's fine, but be honest with yourself about your reasons.
I am trying to be honest, if you are correct and I can make custom cases really cheap, then I just haven't found the right case manufacturer yet. But "cheap" is relative. Many would say 7$ for a custom case is cheap, but when the product without case would cost something between 20-30$, then that 7$ are expensive. I cannot incorporate that into the existing price because then I would be selling the thing below material costs, and increasing the price by the case's could easily take it over 30$, which a lot of people will find just simply too expensive for a UART converter.

As far as conformal coating is concerned, I stand by my point it is unreliable as a replacement for a case, which is what we are talking about here. In itself it is of course reliable when applied for its designated use, that is, for PCBs inside a case for protection against chemical wear/oxidation, increasing insulation etc., but it is not a case replacement. If this doesn't seem to "coincide with practical experience" for you, please show me a commercial portable product where conformal coating was used instead of a hard case.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #37 on: April 22, 2018, 07:39:21 pm »
Digi-Key does value-add enclosures, FWIW.  I haven't quoted them yet but it can't be too horrible.  I'd think it's worth looking into for 100s+.

Hi, thanks for the tip. I've looked into it, what I've found at DigiKey were the Bud Industries cases they are selling in cooperation. I haven't quoted them either, but the prices for unmodified cases (by Bud that you can optionally customize) are online, and they sell for 10$ unmodified. Customized they will surely cost even more. This is unfortunately not acceptable, the muArt is too cheap to have a 10+$ case.
« Last Edit: April 22, 2018, 07:42:18 pm by pylo »
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #38 on: April 22, 2018, 07:58:15 pm »
Case wise, using a potting box with the PCB as top cover (like Dave's µCurrent) would seem like a good and cheap solution. I've used that technique myself for low count projects (5 pieces), and I was happy with how it turned out. It certainly helps to mitigate ESD stuff and improves general mechanical robustness if you can't actually touch any circuitry and only the connectors are exposed.

This can work. I can get such cases for under a dollar. This requires a design with double-sided assembly, which means if I go for this solution, I should not sell the muArt without a case. Which if perfectly fine by me, as long as the case is not too bulky.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #39 on: April 22, 2018, 08:07:28 pm »
No DSR?    On adapter like this  at minimum I'd like to see both CTS/RTS and DTR/DSR pairs, and ideally all signals...

DSR, RI and DCD are the only UART signals I haven't made available. If I wanted to make all signals available, I'd need to incorporate a 3rd isolation IC, which is really expensive, for AFAIK barely any benefit. And that'd still be the case even if I left out the GPIOs. Second, I have yet to see any electronics that uses those signals. I know they are part of UART and heard they are used in modems, but in modern electronics I have yet to see a use for them. Even DTR is only around because there are many boards that use them for controlling the RST line during flashing.

Is there some specific reason you'd like to see DSR included? A board that needs it? Or some other (preferably non-exotic) use case I'm not aware of?
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #40 on: April 24, 2018, 08:15:42 pm »
I see how many of you are interested in having a proper case. So I'm not giving up on that yet and I am actively looking at different solutions. I have some ideas that need further exploration and have already contacted companies. Give me a week or so and I will come back on the topic of a case, hopefully with some results.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #41 on: May 01, 2018, 07:56:48 am »
Hi Everybody, I'm just here to give a short update. There is a prototype case in the making, and the layout of the board will be revised to make it nicely mountable inside the case. According to the case's manufacturer, its cost should be fairly acceptable even for this product in the quantity that I set as the goal for the campaign. We'll see, but it surely sounds promising. The revised layout also centers the USB-receptacle, which is better for multiple reasons, new case or not.

As always, I'll be back if there are news or any questions to be answered. I'm listening for your feedback, so don't stay silent if you've got anything to say.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #42 on: May 06, 2018, 08:16:09 am »
Hi All, I'm here with news again. The first plans for the case are done and it turned out really cool. I've attached a CG render to the OP, go take a look ;) Note that there might be slight differences to the real one, like how translucent the housing really is (I've yet to see it myself), but you get the gist.

There are some nice tricks in there to keep the costs low. The play with transparency and translucency - beside making it look even cooler - helps to keep the labels readable without having to print a silkscreen or stickers, and as a side benefit it guarantees the labels will never come off. There is also no need for windows, holes or separate photoconductive parts just to keep the lights visible. The design is completely screwless, which simplifies assembly a lot.

The layout of the board itself has been revised a bit, but mostly just to center the USB receptacle. It turns out the case itself probably won't need any design changes of the board, so the board is just as compact and neet without the case as it is with it - another big plus. Not to mention the PCB didn't get any larger, quite the contrary, it has become even smaller in this revision. The board is now only 50.2 x 23.5mm, which makes it about the same width as a 2-euro coin, and is about as long as two of them. Since the case is custom manufactured to fit around the board tightly, it doesn't make things a lot bigger either - my point here is, even though the muArt has a lot more components than others and even a case, the high integration and custom case still make it really small, just take a look at the OP's picture to see the comparison with a coin, it is soooo cool...  8)

By the way, I want to thank tec4data for their design of the case. They will also be the one manufacturing it, and they claim they can keep the costs within my limits, including one-time costs! So a big Thumbs Up and Thanks to them.

Next steps? I should be getting a 3d-printed prototype of the case by the end of next week, that will be the first time I'll have one in my hands. The material will be way off, but hey, the final ones will be injection molded. As for the electronics, because I knew I was going to make changes to the layout, I held up prototype production until now. But unless testing tells me otherwise the board is basically final now, so no more expected delays from this point on. Actually, first thing next day I'm placing orders.
 
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Online Monkeh

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Re: myuArt - A UART converter finally done right
« Reply #43 on: May 06, 2018, 08:18:15 am »
Now that's a pretty nifty little case.
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #44 on: May 16, 2018, 05:51:12 am »
Just a small status update since it's been some time. I've ordered the prototypes as promised, in total they ship in about 3 weeks, which means only 2 more left, so I should have them approximately by the end of this month. With them in my hands, I'll be able to test not only the circuit itself, but also how well they fit into the (prototype of the) case. Until then though there isn't too much to report, which is the reason for the apparent silence in the past week. So I guess there will be a lack of updates in the next two weeks too, but just until I receive the units.

Until then you could help me with one thing though. This is my first time doing crowd funding. Where do you suppose I can promote the upcoming campaign (or promote it once it is running)? Any sites, blogs, forums that you think could be interested in the muArt? Hackaday seems like an obvious choice, mikrokontroller.net (a german forum), hackster.io, maybe a reddit etc. Any ideas? I'd also be glad to send one to Dave and others, but frankly I don't know others  :palm:  I'll have 13 in total (minus those I destroy during stress test  >:D) and I'd be happy to send out a couple to bloggers and forumers.
 

Offline Maxlor

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Re: myuArt - A UART converter finally done right
« Reply #45 on: May 16, 2018, 07:13:37 am »
Sounds cool! Of course, sending a prototype to Dave is a gamble, timing-wise! Who knows whether it'll take 1 or 6 months for him to show your device  ???

Btw, for those of us that might maybe do something similar, i.e. a small run for some project that others might be interested in, would you be willing to talk a bit about the design process and costs for the case? At least for me it's  surprising that a custom injection molded case is possible!
 

Offline MattSR

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Re: myuArt - A UART converter finally done right
« Reply #46 on: May 16, 2018, 08:38:44 am »
Hi Pylo!

Can you share the name of the case manufacturer? I’ve been searching for a very long time for a suitable case manufacturer for a smallish project of mine, and the translucent design you have looks great!

Cheers,
Matt
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #47 on: May 18, 2018, 07:31:45 am »
Hi Pylo!

Can you share the name of the case manufacturer? I’ve been searching for a very long time for a suitable case manufacturer for a smallish project of mine, and the translucent design you have looks great!

Cheers,
Matt

The company is called tec4data (tec4data.com), they are a located in Austria in Europe (I'm from Hungary, so they're relatively near to me). They offer design services and production. Good luck and I hope they'll be able to help you too.

Btw, for those of us that might maybe do something similar, i.e. a small run for some project that others might be interested in, would you be willing to talk a bit about the design process and costs for the case? At least for me it's  surprising that a custom injection molded case is possible!

I'll try, but I'm afraid I might disappoint you. The reason is, I have literally zero experience in mechanical CAD design, so after some consultation with tec4data, they basically did all the work. Nevertheless I know it was a gigantic help for them that I had a proper 3D model of the electronics, including not just the PCB, but also the components on it. So I advice others too to make sure you maintain a nice 3D parts library for your project, so that when the time comes, you can make a STEP file export. The case manufacturer then asked me some questions, like "do I want to keep the pin headers pointing upward", and they also made sure we agree on where LEDs and printed text will be positioned. Actually pretty basic stuff, nothing I was surprised about. I already made prior thoughts about these issues, and since I wanted to keep the PCB in a form where it lends itself equally well to a case-less product as well as one with a case, I already had the answers on me. Then they just did their magic for about a week and came back to me with (again a STEP) model of their design. The rendering that you see in the OP was made by me already, after they explained what their idea about the materials was. I briefly showed them the rendering before posting here just to make sure this is how they also imagined it.

Injection molding is normally pretty expensive. Not the per-piece cost, but the setup and tooling costs. These are usually somewhere in the 5k-30k$ range depending on a lot of things, which is why I ruled it out by experience in the beginning. tec4data will only give me an official quote once we've tested the fit of the board into the prototype cases that they print. I've visited them and they have a crazy large and expensive professional 3D printer locally that they use for prototypes. This is not one of those portable bench-top 3D printers that pop up every week on kickstarter, but one that is in the several hundred thousand euros price range. Needless to say, it prints really high quality (I've seen it!). But back to the original topic, they promised me that the absolute upper bound for the case will be 3$/pcs (meaning it will probably cost less), and that one-time costs will be a lot less expensive than the numbers above so I "need not worry". They said this after I made sure they understand the finances of this project (that is, that it is crowdfunded, the end-user price range, and the likely quantities to be sold). I know this sounds vague, but as I said, I need to wait for the mechanical fit tests, only then will I get a quote. But even then, whatever the prices will be, I will need to ask if their quotation is public - I didn't ask this question yet because there is also no official quote at this point, so it seemed like jumping too much ahead.
« Last Edit: May 18, 2018, 07:34:18 am by pylo »
 

Offline Maxlor

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Re: myuArt - A UART converter finally done right
« Reply #48 on: May 18, 2018, 08:04:14 am »
Thanks pylo, that's very interesting. Not disappointing at all, since I don't really have 3D design/machining skills either. So far I've been matching PCBs to existing cases, it's actually good to hear that it is possible to do it the other way round even if you're not an expert.

I think it's pretty cool of them to do this much for you, when there's no guarantee that the crowdfunding will work out. What did you tell them that your minimum order count was going to be? I'm guessing a few hundred pieces, which means a high 3-digit sum for them overall as worst case? From what little I know, that doesn't seem profitable, especially given that they fronted the design work too (don't overestimate that; I've seen how quickly people who know SolidWorks can create designs, I'd guess 1-2 hours for your case? – but of course those people ask for a decent salary too!) So either they think your device is going to be successful and sell more than the bare minimum, or maybe they're hoping to get some word of mouth advertisement through you? Either way, they seem cool, I'm looking forward to reading how it all works out. And of course, you'll have my support once you launch your kickstarter  ;)
 

Offline MattSR

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Re: myuArt - A UART converter finally done right
« Reply #49 on: May 18, 2018, 03:04:09 pm »
Thanks for the info pylo!

One thing I need for my project is a special connector (with ten contacts and a small screw thread) to be integrated into the case. Through your dealings with them, do you think this is something they might be able to accommodate?

Cheers,
Matt
 

Offline Kean

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Re: myuArt - A UART converter finally done right
« Reply #50 on: May 19, 2018, 01:39:54 am »
Sounds to me like they are looking at Aluminium or soft tooling.  Soft tooling seems quite likely if they have a high end 3D printer, as they can easily 3D print masters to make the soft tooling which can only be used for a limited number of "shots".

A bit of info here:
https://www.stratasysdirect.com/technologies/urethane-casting/soft-tooling-vs-hard-tooling
 

Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #51 on: May 19, 2018, 07:35:58 am »
One thing I need for my project is a special connector (with ten contacts and a small screw thread) to be integrated into the case. Through your dealings with them, do you think this is something they might be able to accommodate?

Do you mean something like with OBD-II adapters, where the case is part of the connector? I see no reason why they couldn't, if you look at their homepage, they've done some interesting things in the past (hearing aid, video glasses etc.). Talk to them, that is the sure way.

What did you tell them that your minimum order count was going to be? I'm guessing a few hundred pieces, which means a high 3-digit sum for them overall as worst case?

I told them that my goal is to get 250 pre-orders. Also that, if it is a bit less (say 200), I will still go into manufacturing, but if a lot less, say, 150, I'll be ready to scratch the idea of a custom case (and well, maybe even the whole campaign, otherwise I'd need to adjust the prices, but that'd be problematic for all those who already placed an order).

And of course, you'll have my support once you launch your kickstarter  ;)

Thanks  :-+  I'm targeting Crowd Supply, mainly because I like how they give a little bit of mentoring, which is ideal for someone like me who has never done this before. And of course, the muArt also aligns well with their theme and target audience. I've already contacted them a couple of weeks ago, unfortunately they are really busy and their review queue seems to be long, so I need to be patient. I hope they'll get to me soon now.
« Last Edit: May 19, 2018, 07:37:39 am by pylo »
 

Offline SL4P

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Re: myuArt - A UART converter finally done right
« Reply #52 on: May 19, 2018, 09:18:10 pm »
I realise this is a bit pedantic, and I quite like the idea of your project... but you do realise it has nothing to do with a UART ?

In 95% of modern circuits, and 100% of traditional circuits - the UART functionality is within the controller or a dedicated peripheral chip.

One possible name could be... myUSBIO
As its functionality lies between the USB interface, and the serial i/o side of the UART/serial interface.
Don't ask a question if you aren't willing to listen to the answer.
 

Offline Cerebus

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Re: myuArt - A UART converter finally done right
« Reply #53 on: May 19, 2018, 11:45:17 pm »
I realise this is a bit pedantic, and I quite like the idea of your project... but you do realise it has nothing to do with a UART ?

In 95% of modern circuits, and 100% of traditional circuits - the UART functionality is within the controller or a dedicated peripheral chip.

One possible name could be... myUSBIO
As its functionality lies between the USB interface, and the serial i/o side of the UART/serial interface.

You do know what UART stands for, right? I think a Universal Asynchronous Receiver/Transmitter is a perfectly reasonable description for this project. It is universal, it is not dedicated to one task, and it does indeed receive and transmit asynchronous serial signals.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline SL4P

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Re: myuArt - A UART converter finally done right
« Reply #54 on: May 20, 2018, 03:10:40 am »
hehe, I did say ‘pedantic’...   ;)

Have you ever designed a UART into a project  ?
A significant part of a UART is the ‘shift registers’ to serialise and de-serialise the data either side of the ‘serial link’.
https://en.m.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter

Nowadays. this hardware is ‘hidden’ within a microcontroller (it’s still there), but a long time ago, the functionality was more obvious as an external peripheral chip.
https://en.m.wikipedia.org/wiki/16550_UART
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Offline pylo

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Re: myuArt - A UART converter finally done right
« Reply #55 on: May 20, 2018, 07:34:23 am »
I realise this is a bit pedantic, and I quite like the idea of your project... but you do realise it has nothing to do with a UART ?

In 95% of modern circuits, and 100% of traditional circuits - the UART functionality is within the controller or a dedicated peripheral chip.

One possible name could be... myUSBIO
As its functionality lies between the USB interface, and the serial i/o side of the UART/serial interface.

Haha, challenge accepted ;D

Short answer: While "UART" ist originally a hardware peripheral, today it is used equally often to refer to the protocol (or, well, to UART-like protocolS). Since the muArt converts to/from a UART protocol, and obviously also has a UART peripheral inside (in the bridge IC), you should at least agree it does have a lot to do with UART, even if you dispute if itself is a UART or not. If you look at it this way, having "UART" in the name is not such a far fetch. And of course, what Cerebus said also holds.  But...

Long answer:

Seeing your proposal for another name is myUSBIO, I think I see the real problem. I think you misinterpreted the name as "my-UART", but that's not how I imagined it. The name is artistic and playful, and was never meant to imply that the product itself is a UART peripheral in its original sense as you described. It is only mean to signal that it has something to do with UART. Very importantly, the project's name is written correctly as in this post's attachment. I originally used this spelling in the OP too, but the forum software couldn't display the Greek "mu" correctly and it replaced it everywhere with a question mark (which is also why I had to attach it as a picture here instead of spelling it out). This of course made it unreadable, so I then corrected the contents of the OP to spell "muArt", and used that ever since, but only here in the forum. How should you read it? Definitely not "my-UART". It might also be tempting to pronounce it as "microART", but I'm planning to use that for other projects in the future (and so btw dibs on that :) ) . Since the Greek "mu" is often substituted by "u" in simple text processing, and since that makes it read like "uart", and since the product is actually a UART converter, you can read it as either "mu-Art" or "myu"-Art, playfully combining the Greek "mu" with the "yu" of UART. (And obviously it is a work of Art ;D) Well, the process of naming was kind of the other way around, but that doesn't matter, the logic behind it is still the same. Now, by mistake I wasn't consistent and used the "myu"-form in the OP title (which I now corrected), giving opportunities to misinterpretation.
« Last Edit: May 20, 2018, 07:39:32 am by pylo »
 

Offline SL4P

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Re: muArt - A UART converter finally done right
« Reply #56 on: May 20, 2018, 07:44:27 am »
Yep, I was wrong to cast ‘my’ into the alternate name...
Perhaps mUART... or mUSBIO?

Is there a processor within the device as you suggest? , or simply level converters & isolation?

Sorry, I realise this is all a distraction, but I hate seeing well intended discussion teaching newbies the wrong terminology because ‘it’s convenient or sounds good’.

No disrespect intended, as I said, myself and others think it’s a cool product idea.
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Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #57 on: May 20, 2018, 07:58:25 am »
Is there a processor within the device as you suggest? , or simply level converters & isolation?

The bridging between USB and UART is done by a Silicon Labs CP2102N. This almost certainly has a microprocessor inside, but it is not user-programmable (though there are some parameters you can program). Another IC, a MAX14932 takes care of both the level conversion and the isolation in one step.
 

Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #58 on: May 28, 2018, 04:01:24 pm »
Hi everybody, I’ve got some updates to report from last week :)

First, CrowdSupply came back to me, they apologized that they have been so busy, and we’ve been in touch ever since. Communication has been really smooth, we’ve already executed a contract (they call it the “Statement of Work”), and both parties are now hard at work to bring you the muArt. So I just wanted to say, the campaign will definitely happen.

I’ve also received the first prototypes for the case, and I’ve got to say, I’m thoroughly impressed. Pictures are attached at the end of this post (note that the material used for the prototypes is some kind of epoxy, and it is not what the final cases will be made of – the final ones will be plastic, generally translucent, clear transparent in areas around labels, and will not have any of this yellow-ish color; see the rendering in the OP to get an idea).

The two parts of the case snap together perfectly without seams and hold together securely, yet can still be separated afterwards despite how brittle this epoxy is. The quality of the print is very high, you can see this by the absence of staircasing along the slopes of the case in the picture where I show the USB from the side – the case has not had any kind of post-processing except the removal of supporting material, yet despite this it still hasn’t got any jagged edges. This high quality printing is important and greatly reduces risks. It means that the final cases from the mold tool will likely be alright too. The stripes on the top cover are an artifact of the 3D print and will not be there in the production cases. However even in the prototypes, they are present only optically, for the fingers the top feels perfectly smooth.

I am also happy about the ergonomics. Having those snap points for the fingers works great, and you can easily and securely grab the case by those despite how compact and small it is.

This doesn’t mean though the design of the case is final. If nothing else, the labels of the LEDs need to be made larger. Even though they are readable (just barely), they are simply too tiny. Also, I’ve yet to receive the electronic prototypes, so there is still a chance that the fit of the board isn’t perfect. But this is a great and very promising start. Please cheer for the boards to also turn out great.
 
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Offline NW27

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Re: muArt - A UART converter finally done right
« Reply #59 on: May 28, 2018, 06:04:13 pm »
hehe, I did say ‘pedantic’...   ;)

Have you ever designed a UART into a project  ?
A significant part of a UART is the ‘shift registers’ to serialise and de-serialise the data either side of the ‘serial link’.
https://en.m.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter

Nowadays. this hardware is ‘hidden’ within a microcontroller (it’s still there), but a long time ago, the functionality was more obvious as an external peripheral chip.
https://en.m.wikipedia.org/wiki/16550_UART
Your showing your young age :)
It was the Z80 SIO followed closely by the INS8250 that popped into my mind, for stand-alone uarts.

Sent from my SM-N920I using Tapatalk

 

Offline ThaHandy

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Re: muArt - A UART converter finally done right
« Reply #60 on: May 30, 2018, 06:22:40 am »
Aww. missed it again.
Was about to ask if if could be RS485 compatible
I really could use some cheap but reliable isolated RS485 interface  ::)
 

Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #61 on: May 30, 2018, 06:43:20 am »
Aww. missed it again.
Was about to ask if if could be RS485 compatible
I really could use some cheap but reliable isolated RS485 interface  ::)

Well you just need to ask ;) Coz' the thing is, you can use the muArt as such. The GPO pin can be repurposed to function as the DE pin to be used in RS485. This is one of the hidden design considerations that I am not actively marketing, but planning to make a post about during the campaign and mention in the datasheet too.
 

Online ogden

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Re: myuArt - A UART converter finally done right
« Reply #62 on: June 02, 2018, 07:18:26 am »
And obviously it is a work of Art ;D

Self-proclaimed Artists shall be very careful sticking "art" labels before critics and/or buyers do ;)

I would suggest to reconsider naming & logo, stick with uUART.

[edit], yes, it kind of breaks "my UART" idea by meaning "micro UART", but definitely less confusing.
« Last Edit: June 04, 2018, 03:43:57 am by ogden »
 

Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #63 on: June 03, 2018, 10:14:32 pm »
I've got great news! The prototype boards / electronics have arrived, and they work perfectly. I've been testing various aspects most day yesterday, and it seems like these boards will also be the final design. Meaning this design would go 1:1 to volume production if the campaign over at CrowdSupply is successful. All features work as advertised, communication (of course), handshaking, speeds up to 3Mbaud, protection circuits, the whole voltage range, GPIO, LEDs, and whatever I left out too. USB was stable even at well over maximum allowed cable length (tested @ 6m), and my scope confirmed that signal transitions on the other side of the isolation are clean and well-defined. The USB receptacle mates solidly and holds my chosen cables (which btw will also be available in a pledge level) tightly, so no chance for loose connections there. The boards seem to fit well into the prototype cases too.

Beside Windows, I also tested on Linux, and the mainline drivers - which are available even in old kernels - are solid as expected. Here on Linux there are two small limitations though. One is that the driver "only" supports speeds up to 2Mbaud, which is TBH still about 20x more than the highest rates I've seen in commercial peer devices (115200), so this is more than OK. The other is that the GPIOs under Linux are only usable if you replace the mainline driver with the one from the SiLabs website - note this limitation only concerns the GPIO pins under Linux, not the UART communication which works out of the box. Also note that the GPIO input LED works out of the box irrespective of OS or drivers, because this doesn't depend on the USB stack at all.

Below is a picture of the board I took with my 10 year old camera (of which I hacked the firmware myself BTW). Due to the importance of this picture you can also find it in the OP.

The arrival of these boards is a really important milestone. The fact that they work as expected and as advertised is even greater (though these are simple boards compared to those I've been doing for work lately). As the next step, my #1 goal now is to get the campaign pre-launch page up and running. Interested people will be able to subscribe there to get notifications about the campaign, which will come once all preparations (creating images, text, video, marketing prearrangements etc.) are done.
« Last Edit: June 03, 2018, 11:06:10 pm by pylo »
 

Offline pylo

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Re: On CrowdSupply Now: muArt - A UART converter finally done right
« Reply #64 on: June 10, 2018, 03:04:23 am »
Hello Everybody, the muArt is now in pre-launch! Visit CrowdSupply and subscribe to get project updates and important notifications about the campaign so that you won't miss it.

Link to muArt @ CrowdSupply
 
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Offline NorthGuy

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Re: muArt - A UART converter finally done right
« Reply #65 on: June 11, 2018, 01:14:11 am »
I’ve also received the first prototypes for the case, and I’ve got to say, I’m thoroughly impressed. Pictures are attached at the end of this post (note that the material used for the prototypes is some kind of epoxy, and it is not what the final cases will be made of – the final ones will be plastic, generally translucent, clear transparent in areas around labels, and will not have any of this yellow-ish color; see the rendering in the OP to get an idea).

The enclosures of the front page of your campaign look even better. May I ask you who's making such nice custom enclosures for you?
 

Offline Cerebus

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Re: muArt - A UART converter finally done right
« Reply #66 on: June 11, 2018, 02:22:11 am »
I’ve also received the first prototypes for the case, and I’ve got to say, I’m thoroughly impressed. Pictures are attached at the end of this post (note that the material used for the prototypes is some kind of epoxy, and it is not what the final cases will be made of – the final ones will be plastic, generally translucent, clear transparent in areas around labels, and will not have any of this yellow-ish color; see the rendering in the OP to get an idea).

The enclosures of the front page of your campaign look even better. May I ask you who's making such nice custom enclosures for you?

The details are all in this thread already.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #67 on: June 11, 2018, 02:40:07 am »
The enclosures of the front page of your campaign look even better. May I ask you who's making such nice custom enclosures for you?

https://www.tec4data.com/
 

Offline NorthGuy

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Re: muArt - A UART converter finally done right
« Reply #68 on: June 11, 2018, 04:37:51 am »
The details are all in this thread already.

I'm sorry I missed it. I hardly managed to find it Today even after you said it was there. Difficult to sift through numerous linguistic discussions :)

https://www.tec4data.com/

Thank you. By the Web site, the company looks very expensive. Did they allow you to publish their final prices?

I designed an isolated USB<->UART converter once using PIC16F1454 and SiLab isolators. It could only do 2Mbaud, but it used HID, which limited the data rate, so the effective sustainable full-duplex rate was only about 60KBytes/sec.

Wish you good luck with your campaign!
 

Offline pylo

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Re: muArt - A UART converter finally done right
« Reply #69 on: June 12, 2018, 06:45:38 am »
Thank you. By the Web site, the company looks very expensive. Did they allow you to publish their final prices?

There is still a small modification to the case coming, I don't have final prices yet. I'm simply sticking to their promised maximum price in my calculations.
 

Offline pylo

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Re: On CrowdSupply Now: muArt - A UART converter finally done right
« Reply #70 on: June 20, 2018, 01:11:30 am »
Look what I've found over at MickMake about the muArt: "This is definitely one for your toolbox."  :)

Starts at 4m16s into the video.


 

Offline pylo

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Re: On CrowdSupply Now: muArt - A UART converter finally done right
« Reply #71 on: July 23, 2018, 09:27:39 am »
Hello Everybody!
The campaign launch is nearing, but if you are subscribed already, you'll get notified anyway ;)

The real reason I am writing now, is because I am looking for reviewers in exchange for free muArts. This is the ideal way to get a muArt now without having to wait for months for the end of the campaign and batch manufacturing. And for "free". The rules are simple:
  • I send you a muArt before the campaign, and you write about it in your blog/vblog in English.
  • You are free to write what you want. I won't bind this offer to a positive review (but I'm free to not to backlink).
  • As a Thank You, you can keep your muArt, and you also get traffic from backlinking from the campaign page.
  • If you are interested, let me know in a PM. I'll need your (v)blog's address in advance, and obviously, later your name & postal address to be able to ship you a unit.
  • Samples are limited in quantity and were expensive to produce. I reserve the right to choose who gets one.
Injection molding will be only possible once the campaign succeeds. So while the electronics are final, please understand that the enclosures of review samples are different in material, texture and color to the final ones. Reviewers are entitled to also get a final case once the campaign succeeds should they request it.
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #72 on: August 08, 2018, 06:47:27 am »
Hello Everybody!

It's been a very busy few weeks (months?) for me with all the preparations, but I'm pleased to announce that the campaign has gone live and the muArt is now accepting pledges!

Special thanks to all the folks here on the EEVBlog board, as it was your wishes that resulted in the creation of the enclosure of the muArt, and the enclosure is now standard accessory for all backers.

Wish me luck ;)
« Last Edit: August 08, 2018, 06:57:37 am by pylo »
 
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Offline iainwhite

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #73 on: August 09, 2018, 03:38:13 am »
Good luck!

I backed it.
 

Offline Jon.C

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #74 on: August 09, 2018, 05:30:59 am »
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #75 on: August 09, 2018, 08:58:56 am »
Yes, you'll need the CP210x VCP drivers. You'll also be able to get them much more easily from the muArt's homepage, but that's under construction. You'll also find a much better Linux driver there, though I have to say the one in standard mainline also works. Keep a lookout for project updates over at CrowdSupply for more info ;)
 
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Offline grizewald

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #76 on: August 09, 2018, 09:09:43 pm »
Great to see this live at last.

I've just added my backing as well and I'm really looking forward to being able to get rid of my pile of USB-Serial converters!

 :-+
 

Offline EEVblog

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #77 on: August 09, 2018, 09:18:07 pm »
Do you have to add the VCC line to the target? (presumably to power the level converter)
Forgive me if it's mentioned somewhere, I haven't looked at everything.
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #78 on: August 09, 2018, 10:07:05 pm »
Do you have to add the VCC line to the target? (presumably to power the level converter)
Forgive me if it's mentioned somewhere, I haven't looked at everything.
No prob :) Yes you need that, in the latest version of the board this pin's also been renamed to VIN to emphasize that this is an input pin. In my experience every prototyping board / SBC out there already has a header for GPIO or core voltage, so I prefer very much having to connect one wire more and then everything being automatically correct, instead of having to set voltages manually. And for your own custom boards you can either place this pin too, or in case you cannot, just supply it externally, but IMHO the latter is kind of rare.

Here's an interesting thing: I deliberately made the PWR LED only light up when both USB and VIN are connected. This way you can actually tell when the whole board's powered correctly, unlike with other converters where this LED simply signalizes USB connection but is actually useless because it doesn't mean power has been correctly applied everywhere.

Aaanyway, last week I posted a sample for your mailbag, with schematics and a preliminary datasheet. If there's a mail from Hungary, that's probably it :)

And thanks Dave for the great vblog!
 

Offline Jon.C

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #79 on: August 09, 2018, 10:42:45 pm »
backed !

almost there

 

Offline EEVblog

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #80 on: August 10, 2018, 12:27:25 am »
Here's an interesting thing: I deliberately made the PWR LED only light up when both USB and VIN are connected. This way you can actually tell when the whole board's powered correctly, unlike with other converters where this LED simply signalizes USB connection but is actually useless because it doesn't mean power has been correctly applied everywhere.

Nice touch.

Quote
Aaanyway, last week I posted a sample for your mailbag, with schematics and a preliminary datasheet. If there's a mail from Hungary, that's probably it :)

Cool, thanks.
 

Online BNElecEng

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #81 on: August 10, 2018, 06:41:05 pm »
Just backed the project. Good luck!
 

Offline NorthGuy

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #82 on: August 11, 2018, 07:33:38 am »
Congratulations, it's funded  :-+

I've read your update on safety. I think it's a good idea to add to the discussion one more case - negative voltages. If they poke a ground wire into VIn then there will be negative voltages on other pins.
 

Offline chriswebb

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #83 on: August 11, 2018, 09:00:33 am »
Backed it!
Always learning. The greatest part of life is that there will always be more to learn.
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #84 on: August 11, 2018, 05:18:25 pm »
Congratulations, it's funded  :-+

Thank you guys for your support! I was contemplating between 7-8 week campaign period, and went for 7 weeks only because I wanted to make sure I can ship before December (to avoid Christmas season where shipping delays go out of control), but I'd have never imagined the project gets funded in just two and a half days. I'm so glad and thank you.


I've read your update on safety. I think it's a good idea to add to the discussion one more case - negative voltages. If they poke a ground wire into VIn then there will be negative voltages on other pins.

Good point to bring this up too. The ESD diodes were chosen to be bidirectional for exactly this reason. If you connect your data lines before the power, and you reverse the polarity on power, then your data signals may be negative. Unidirectional diodes would start conducting and your own board's digital outputs would see it as a short, so there's a good chance your application would burn down. Bidirectional diodes avoid this short, but now the muArt will probably get damaged instead. This is however the more preferable way, because I'd rather protect the application circuit. You may not have a replacement for your custom circuit at hand, but a UART adapter is easily replaced. The adapter is also probably way cheaper than whatever circuit is hanging on its IOs. So, for both of these reasons, if I have to choose which to preserve like in this case, I'll save the application.

Of course, if you connect power first and only then the data lines, the picture looks different. As I've mentioned in my earlier post, I've made the power LED light up only when power on *both* sides of the muArt have been correctly applied. This means you can immediately recognize if the VIN polarity is wrong (LED won't light up), so you can correct it before attaching any IOs, and all is good.

EDIT: I've incorporated these points into the original article, but I need CrowdSupply to publish the changes. They'll probably do it after the weekend.
« Last Edit: August 11, 2018, 05:59:07 pm by pylo »
 

Offline Jon.C

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #85 on: August 11, 2018, 09:54:54 pm »
Hi  @pylo

So is it possible to have them before November?

or continues the campaign to the end?

Thank you
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #86 on: August 12, 2018, 06:52:01 pm »
Hi Jon,
The campaign will run to its end. But being funded early does mean I can make some preparations earlier, which should at least lessen the probability of delays.
 
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Offline edgarasf123

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #87 on: September 01, 2018, 09:02:08 am »
Seeing this is being marketed to replace all USB to TTL devices, I have one issue. How would I connect this to a serial port that only offers 3 pins: GND, TXD, and RXD? There is no 3.3v pin.



I own 2 devices that use audio jack: TI-83 and router.
« Last Edit: September 02, 2018, 02:06:15 am by edgarasf123 »
 
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Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #88 on: September 02, 2018, 02:45:12 am »
Hi!

Normally you'd connect the VIN pin to the 3V3 header of the device with an extra jumper cable. If your devices are housed in and you cannot open them like in your case, you need to supply the VIN pin of the converter with an external 3V3 regulator (for example a lab supply), making sure ground of the 3.3V is also connected to GND of your serial cable.

I accept the critique that in such cases you'll have an easier job with a fixed voltage 3.3V converter, though I could argument it is not the UART adapter limiting you - which *can* speak to your router and TI-83 - but the fact that a wire in the cable is not present, so it is merely a connector problem. But as I said, you can connect the adapter to any other voltage source as long as it matches the level of your IO and both are referenced to the same ground.
 

Online analogo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #89 on: September 13, 2018, 05:11:37 am »
Would it be possible add to the CrowdSupply campaign/shop also the possibility to order the nice cable I see in the pictures, the one one with an IDC at on end and many dupont female connectors, each marked with a tag, on the other end?
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #90 on: September 14, 2018, 03:18:29 am »
Would it be possible add to the CrowdSupply campaign/shop also the possibility to order the nice cable I see in the pictures, the one one with an IDC at on end and many dupont female connectors, each marked with a tag, on the other end?

Hi analogo! That cable is included in the Cable Bundle. So if you pledge for a muArt Kit instead of a single device, you'll get that cable :)
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #91 on: September 21, 2018, 07:41:34 am »
Hi Everybody!

The last time I posted about campaign progress was when it launched, and that was six weeks ago. In-between I obviously didn't want to spam about it by posting at every possible milestone, even though the campaign has been a great success with 266% of the $7k goal reached. The end of the campaign is nearing though with only less than a week left, so I'm taking this opportunity to remind you that the next few days are your last chance to back the project, and to get your own muArt at the current price.

https://www.crowdsupply.com/pylo/muart

Even if you've already checked out the project, I recommend you take a look at the project updates posted on Crowd Supply, as they contain quite a few bits of interesting information. Though I'm sure many - especially visitors of this forum - will be familiar with the technical portions, I'm kind of proud that I managed to produce regular updates that are actually informative and aren't just progress updates.

Anyway, thanks for your support and feedback, and remember, only one week left :)
 

Offline Mr.B

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #92 on: September 21, 2018, 08:25:36 am »
Backed.
Well run campaign.
Looking forward to receiving them.
Time is the overseer of all things.
 

Offline xaxaxa

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #93 on: September 21, 2018, 11:04:41 am »
I see that you have replaced the cp2102 with a ftdi part; probably too late to say this but HT42B534 is available from LCSC for $0.3. I would personally never use FTDI parts in a product, and as a user I tend to avoid products that use FTDI parts.
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #94 on: September 21, 2018, 06:00:48 pm »
Hi xaxaxa! The Holtek bridge has already been brought to my attention in this thread, but I couldn't use it for the respin, because it is not functionally equivalent to the CP2102N. The campaign was already running long when it turned out I need a replacement for the SiLabs part, and since I promised GPIOs for the backers and many have already backed the project, I needed to find an alternative component that also has GPIOs. Had I used the HT42B534, I would have needed to remove GPIO from the features which many backers have already pledged for. The only suitable part I found was from FTDI. I know that some of you hold a grudge against FTDI, but I see no other alternative to the CP2102N as long as I want to deliver the features originally promised in the campaign.
 

Offline mrpackethead

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #95 on: September 25, 2018, 03:36:21 pm »
I never want to see another FTDI part ever again. 
On a quest to find increasingly complicated ways to blink things
 

Online ogden

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #96 on: September 25, 2018, 06:09:39 pm »
I know that some of you hold a grudge against FTDI, but I see no other alternative to the CP2102N as long as I want to deliver the features originally promised in the campaign.

There is alternative, but most likely you will not love it: microcontroller with USB interface.
 

Offline mrpackethead

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #97 on: September 25, 2018, 09:02:25 pm »
I never want to see another FTDI part ever again.  but still backed it.

On a quest to find increasingly complicated ways to blink things
 
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Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #98 on: September 26, 2018, 12:35:06 am »
There is alternative, but most likely you will not love it: microcontroller with USB interface.

It is technically an alternative, but probably no one would like it unless the FW to that uC is the product itself. The development effort and even real financial costs - think about testing, signed drivers for windows (even with cdc-acm) -  would be unacceptably high at this stage of the campaign. Developing firmware for such an IC from scratch to make it equivalent to existing pro solutions like an FTDI part with all the possible options (it is more than just getting some characters over with USB) and doing complete validation is more than worth a project on its own, and the muArt is not about that. Case in point, SiLabs for one could not get it right - I have reasons to believe that the CP2102N that I had to replace is secretly an LPC microcontroller in bubblewrap.
« Last Edit: September 26, 2018, 12:38:18 am by pylo »
 
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Online ogden

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #99 on: September 26, 2018, 01:28:59 am »
There is alternative, but most likely you will not love it: microcontroller with USB interface.

It is technically an alternative, but probably no one would like it unless the FW to that uC is the product itself.

Indeed. That's why I said you will not love it. Sorry that from beginning I was not 100% believer in this project. Now I see that you handled it very well and what's important - listened to EEVblog forum members. Case is very neat indeed. Hopefully from now everything will go smooth and backers will be happy.
 

Offline Cerebus

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #100 on: September 26, 2018, 01:52:31 am »
Case in point, SiLabs for one could not get it right - I have reasons to believe that the CP2102N that I had to replace is secretly an LPC microcontroller in bubblewrap.

No, unless you're using LPC in a generic sense instead of referring to the Philips/NXP ARM product line. There's strong evidence to suggest that the CP2102N is a pre-programmed EFM8 which would make a lot more sense as they are both from Silicon Labs.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #101 on: October 01, 2018, 07:57:41 pm »
No, unless you're using LPC in a generic sense instead of referring to the Philips/NXP ARM product line. There's strong evidence to suggest that the CP2102N is a pre-programmed EFM8 which would make a lot more sense as they are both from Silicon Labs.

I was actually referring to the specific manufacturer devices, but you are probably right. My main point though was that even this "hardware" bridge is just a pre-programmed uC, and I wanted to show that developing something like that is not that trivial, as even a big silicon company like SiLabs wasn't able to get it right, even though their possibilities (both in budget and testing) are obviously way greater than of a lonely hacker's.

On a different note: It seems I didn't get into the Mailbag video, but I'll hope for the next one :) Either way funny to me that Dave tested only two gadgets in the current video. Probably because testing the USB scope took up most of the time budget.
 

Offline NorthGuy

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #102 on: October 12, 2018, 04:51:28 am »
Would you share the information how the deal with the enclosures turned out?
 

Offline pylo

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #103 on: October 12, 2018, 11:51:27 pm »
We managed to obtain a used mold and modified it for the muArt's enclosure. It cost me about 2.2k$ one-time, plus the cases are 0.6/piece at an MOQ of 1000. These are solely production costs. As for tec4data's engineering services, we'll work together on other projects (bartered).
 

Offline NorthGuy

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Re: Live on CrowdSupply! muArt - A UART converter finally done right
« Reply #104 on: October 13, 2018, 04:29:38 am »
We managed to obtain a used mold and modified it for the muArt's enclosure. It cost me about 2.2k$ one-time, plus the cases are 0.6/piece at an MOQ of 1000. These are solely production costs. As for tec4data's engineering services, we'll work together on other projects (bartered).

Thank you.
 


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