Author Topic: Is arduino the best?  (Read 27901 times)

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Offline TerminalJack505

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Re: Is arduino the best?
« Reply #50 on: March 23, 2013, 04:13:48 am »
For anyone interested, I've attached a draft schematic of the USB serial cable.  It's based on the design found here.  I've just added some bells and whistles.
 

Offline westfw

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Re: Is arduino the best?
« Reply #51 on: March 23, 2013, 05:58:51 am »
IMNSHO, the tiny2313 does not offer enough cost advantage to justify using it instead of an ATmega8 or similar that has a BIG advantage in terms of code space.  By the time you put VUSB in there, along with some basic ISP programming code, you're really pushing the limits of the tiny2313 (the USBTiny programmer uses a 2313, while the USPASP uses a mega8.  When USBTiny needs a new protocol to handle AVRs with 256k of flash, you sort of look at it and go "oops.   Oh well.")

For that matter, the mega328p seems to be unusually cheap at the moment, from some distributors (It's cheaper than an ATmega88, and even cheaper than some of the attiny2313 variants, from Mouser, for example.)  If you've already got a 2313, that's fine.  If you need to buy a chip, there are better choices.

(Sigh.  I'm running into this more and more.  As a Hobbyist, I've built up a stock of parts that are ... essentially obsolete, and thus not particularly worth using in any design that I might think of "publishing."  (1206 resistors, (real!) 8051 microprocessors, etc.  Sigh again.))
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #52 on: March 23, 2013, 06:21:45 am »
Wow!  Mouser's proud of the ATtiny2313 all right.  Digikey has it at half of their price.

I know how you feel about component stock.  I've got a ton of stuff that will never get used, I'm sure.  That's one of the reasons I'm going to unload some of it on Anson.   :P

I also get frustrated anytime I have to order a part for a design.  The problem is, I need just a couple bucks worth of parts but before I know it I've ordered about 50 or 60 bucks worth--"just in case I need it one day."  That's why I usually have a rule about designing around what I have in stock.
 

Offline Slothie

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Re: Is arduino the best?
« Reply #53 on: March 27, 2013, 11:44:46 pm »
I also get frustrated anytime I have to order a part for a design.  The problem is, I need just a couple bucks worth of parts but before I know it I've ordered about 50 or 60 bucks worth--"just in case I need it one day."  That's why I usually have a rule about designing around what I have in stock.
Tell me about it! I have ~50 2716 EPROMS I bought back in the day because the bulk price was too good to miss and I thought I'd use them eventually. I find these days very few applications.
Somewhat ,more hopeful is the tube of 40 or so opto-isolaters; I use a 2-3 a year so I'm good till about 2028.
I still have a boxful of Z80, 6503 and 6809 processors and support chips but I have a plan for them when time permits.....
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #54 on: March 28, 2013, 12:53:40 am »
Here's a half-baked but mostly complete schematic of the serial cable.  Don't pay any attention to the pin numbers.  Most of the symbols are just using placeholder packages right now. 

The resistor that's just hanging out there (R14) is going to be attached to the MCU once I get around to changing the MCU symbol. 

I still haven't decided what connector I'm going to use so the I/O on the far right is in limbo at the moment.  I'm probably going to use the same pinout as FTDI cables.

The USB connector will likely just be wirepads and a USB cable will be soldered directly to the board.  This is actually required by the USB spec for low speed devices so this hack device will be that much closer to compliance.   ;D

I've been playing around with the circuit on the breadboard and it works pretty well.  The drivers are the real issue with these types of USB devices.  They aren't digitally signed so you have to override an option in Windows 7 64-bit to get them to load.  The device works great under Linux (of course!)  But won't work under a Linux guest OS using VMWare's Player VM.  It enumerates the device, loads the drivers and everything but still doesn't work for some reason.
 

Offline Anson

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Re: Is arduino the best?
« Reply #55 on: March 28, 2013, 02:17:05 am »
Not that I know what I'm looking at but it looks very professional!  :-+ I hope you include instructions. And tech support.  ;D
 

Offline NiHaoMike

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Re: Is arduino the best?
« Reply #56 on: March 28, 2013, 02:26:29 am »
You can use a FTDI cable to bitbang Optiboot onto your homemade Arduino. Then use that to bootload the rest of your chips.

That said, I recommend PIC since the diversity it offers makes it work over a wider range of applications than Arduino. The tradeoff is that the learning curve is a little steeper, but not by much. (I recommend starting with PIC24 or dsPIC33 since both of those are modern and will remain useful for years to come.) You can also look at MSP430 (very limited compared to the others, best suited for low power applications) and STM32 (very cheap ARM boards). There's also cheap wireless routers and the Raspberry Pi, but those are rather advanced embedded systems and not particularly useful for learning about low level programming.
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Offline TerminalJack505

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Re: Is arduino the best?
« Reply #57 on: March 28, 2013, 04:27:36 am »
Not that I know what I'm looking at but it looks very professional!  :-+ I hope you include instructions. And tech support.  ;D

The hardware should be pretty robust.  The only real problem I can foresee is if you reversed the positive remote voltage and ground.  In that case the zener diode on the output is going to conduct and likely fry.  I don't have any polyfuses, otherwise I'd put one on the output to prevent that.  I might be able to put a normal 5x20mm fuse in the design but probably wont have room since I already have an enclosure in mind and the fuse probably wont fit.

I'll definitely do what I can so far as helping you out goes.  Naturally I want you to use the programmer and serial cable since I've put a fair amount of effort into them.  I'll also be interested in your feedback so far as any issues you run across.  You'll be a kind of beta tester in that regard.   :D  If things work well then I might make a few more and give them away to others.
 

Offline Anson

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Re: Is arduino the best?
« Reply #58 on: March 28, 2013, 07:10:13 pm »
Sounds good to me. What size polyfuse? I think I have a couple from some boards.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #59 on: March 28, 2013, 10:16:23 pm »
Sounds good to me. What size polyfuse? I think I have a couple from some boards.

There shouldn't be much current drawn from that voltage source.  100 mA would likely be the worse case.  The maximum allowed voltage for that source will be 5.5 volts.

I'll look around and see what I have.  I might be able to scrounge something up myself. 
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #60 on: March 29, 2013, 10:11:10 pm »
I found some polyswitches on some old boards that should work.  That was a good idea.  I didn't think to check.  I've got four with a holding current of 140mA and a trip current of 280mA so I'll put one on both the input side as well as the output.

Here's the latest schematic.  It should be pretty close to final.  (The pin numbers are still bogus.)  Things still might change due to issues that come up during layout.

Now I need to gather up all the components and define all the packages.
 

Offline Anson

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Re: Is arduino the best?
« Reply #61 on: March 29, 2013, 11:41:09 pm »
It's very interesting following your progress on this. So far I have learned two things, 1 I have a lot to learn, and 2 it takes time and a lot of patience to create a good design. I have been looking up the parts you are using and trying to figure out why they are there but I have yet to figure it out. Maybe later when its finished you can write a bit about your creative process and why you used what part where and why. I will never be an electrical engineer or anything near that level but I would like to further understand the process. Hopefully without getting into a lot of complex math.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #62 on: March 30, 2013, 12:37:36 am »
I plan on writing-up a document that explains the 'raison d'etre' for each of the components once I'm done.  There's a bit of 'lily gilding' going on but that's something that can be done when you're making just a few boards.  Unfortunately, some of the components aren't ideal due to the fact that I'm using just what I have on-hand.

One of my problems will be making everything fit in the enclosure that I plan to use.  I've got an old Belkin device that was used to talk to PalmPilots over USB that I plan to gut and use.  It's a pretty small enclosure, though, so that may not work out.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #63 on: April 02, 2013, 02:00:05 am »
I've attached the latest developments of the virtual COM port project.  The routing is pretty much done but I'm going to have to change the ISP header.  It's too tall for the enclosure so I'm going to just leave some solder pads for it.  This will leave more room for the top pour so that will work out well.

The pour on the top of the board is +5V and the main pour on the bottom is GND.  The PDFs for the board are at 3X size.  The actual board is just 1"x3".

Have you been playing with Atmel Studio and learning C, Anson?  How's that going?
 

Offline Anson

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Re: Is arduino the best?
« Reply #64 on: April 02, 2013, 04:59:46 pm »
Have you been playing with Atmel Studio and learning C, Anson?  How's that going?

Navigating the software is easy pretty much got all that figured out. I have been looking at example codes and trying to understand everything I think I am progressing. Will be much faster though once i can physically create a result. Where would be the best place to ask dumb coding questions once I get started? I hate asking dumb questions to overly qualified people that seem to act like if you don't know maybe you should go somewhere else. Which I have gotten before on other sites.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #65 on: April 03, 2013, 03:10:04 am »
Heck, I'd just start a new thread here in this forum.  There's usually someone that will help you out.

I know what you mean, though.  When it comes to software I'm guilty of that.  Software development is what I do for a living but I'm not particularly interesting in teaching other people about software development.  I hang out in the forum to learn electronics.  Besides, software is way too subjective of a subject.  Practically any discussion regarding software quickly devolves into a pissing match.  Every person and their dog has an opinion when it comes to coding, it seems.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #66 on: April 05, 2013, 06:13:47 pm »
It's been slow going on this project, Anson,  but I'm nearly ready to build the board.

Unfortunately, my CNC controller PC decided to go tits-up.  I'm going to get it replaced next week.  I use my CNC mill to drill my boards.  I may try to drill the holes and vias manually this weekend.  That may not work out so well, though, since those vias are kind of tricky to drill manually.

I've attached the latest schematic.  I don't think there have been many changes since the last time I posted it.
 

Offline Anson

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Re: Is arduino the best?
« Reply #67 on: April 06, 2013, 01:14:05 am »
Looks very professional. Can't wait to get it. Be sure to post some images of the finished product before you send it to me. I'm sure a few guys here would be interested to see it.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #68 on: April 13, 2013, 09:20:47 pm »
This project is finally going to make the move from breadboard to PCB.  The board has been etched, tinned, painted, drilled and cut to final size. 

I still need to solder the 'vias' (bus wire soldered to either side of the board), do a final test of the traces (for opens and shorts) and finally, solder the components to the board.  Hopefully I'll get to at least the vias and testing tonight.

It's not pretty but should work fine.  The top and bottom weren't quite aligned so the holes for the vias are a little offset on the bottom.  I manually drilled the 5 bigger holes instead of letting the CNC mill do them and managed to screw one of them up.  I forgot to retract the bit so the carbide drill bit turned into a router bit.   :palm:  Thankfully it didn't break.

I used hatch pours instead of solid pours.  The 'solder resist' is just glass paint and seems to stick to fiberglass better than metal.
 

Offline NiHaoMike

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Re: Is arduino the best?
« Reply #69 on: April 13, 2013, 10:17:52 pm »
If hatch pours have higher ground impedance and use more etchant in manufacture, what's the point of using them? (Is it just to look "cool"?)
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Offline TerminalJack505

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Re: Is arduino the best?
« Reply #70 on: April 13, 2013, 11:02:36 pm »
If hatch pours have higher ground impedance and use more etchant in manufacture, what's the point of using them? (Is it just to look "cool"?)

I've wondered about that myself.  I don't know what advantages they might have to a solid pour.

Their "cool factor" does seem a little higher, though.
 

Offline Anson

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Re: Is arduino the best?
« Reply #71 on: April 14, 2013, 01:41:59 am »
Wow looks nice.  :-+ What's a hatch pour? Are you talking about the grid like pattern?
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #72 on: April 14, 2013, 03:01:29 am »
Wow looks nice.  :-+ What's a hatch pour? Are you talking about the grid like pattern?

Yes, exactly.  Eagle has the option to create solid pours, hatch pours or cutout pours (don't know what that is.)
 

Offline ptricks

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Re: Is arduino the best?
« Reply #73 on: April 14, 2013, 11:08:32 am »
If hatch pours have higher ground impedance and use more etchant in manufacture, what's the point of using them? (Is it just to look "cool"?)

I've wondered about that myself.  I don't know what advantages they might have to a solid pour.

Their "cool factor" does seem a little higher, though.

Hatch pours are for when you want to avoid the skin effect , are easier to solder to since they don't sink all the heat from the iron, and can allow for more flex in the board if it has to bend a little.
 

Offline TerminalJack505

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Re: Is arduino the best?
« Reply #74 on: April 17, 2013, 11:57:18 pm »
Here are photos of the latest progress on this project. 

All components have been soldered on.  An output connector was rigged-up and soldered on.  The output connector has been epoxied to the board to give it more structural strength whenever the connector is removed.  A squid cable has been made for programming (but hopefully not debugging) the MCU.

Now I just need to let the epoxy cure and then solder on the USB cable and (temporary) programming cable, make an output cable, program the MCU and do a smoke test.  It should be pretty much downhill from here.

The attached schematic is exactly what's on the board.  I may have to change the LED current limit resistor values and a few cap values but it should be pretty close to final.
 


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