Favorite budget USB MCUs

[janoc]

It's not a deal-breaker or anything, but if you're a manufacturer laying out a die, what's the point of moving those port pins all over the place?  Is there a reason you can't have ports in consecutive order, and their alternate peripheral functions also aligned thusly?  Is there something inherent to the core, or some other tangible benefit, that makes it desirable?  Maybe it's just an opportunity to play Where's Waldo with P0.7?

Don't forget that on many modern chips you can remap pins and move the functionality where you need it. It is more playing "Where's Waldo" in the datasheet to find the location where is which function mapped (each pin can have 5-6 alternative functions + you can remap them!) than identifying the physical pins these days.

[dannyf]

you do not have to check the datasheet every single time you lay a pin since you know there's no missing pins like in atxmegas).

That's a dangerous habit.

Also makes code simpler.

Don't see how.

Why would you use an XMega when you can have an STM32F10x or STM32F30x for essentially the same money?

A few:

1) human factors: programmer's capabilities? learning curve? lack of skills? ...
2) software: migrating existing code base can be expensive and sometimes impossible?
3) customer needs: they may not like it?
4) marketing?
5) ruggedness? simpler chips tend to be more resistant to interference.
...

[Dago]

It's not a deal-breaker or anything, but if you're a manufacturer laying out a die, what's the point of moving those port pins all over the place?  Is there a reason you can't have ports in consecutive order, and their alternate peripheral functions also aligned thusly?  Is there something inherent to the core, or some other tangible benefit, that makes it desirable?  Maybe it's just an opportunity to play Where's Waldo with P0.7?

Don't forget that on many modern chips you can remap pins and move the functionality where you need it. It is more playing "Where's Waldo" in the datasheet to find the location where is which function mapped (each pin can have 5-6 alternative functions + you can remap them!) than identifying the physical pins these days.

Well this remap thing is quite silly for some STM32 chip I'm developing for currently. Yeah there are multiple pins for lets say the I2C module... except the multiple pins are right next to each other. So By remapping I get pretty much nothing. Should be spread around the chip to make for a cleaner layout. And all the ADC pins are mainly on the port A. But then most of the peripheral functions are also mapped to mainly on port A. So if I need a bunch of ADC pins it gets very difficult to have enough pins for the rest of the stuff, gah. And currently I'm using two timer channels with complementary outputs and you'd assume the outputs would be close to eachother... but nope, these are spread around the MCU without a chance to route them in a clean way.

So far my experience with STM32 is that nobody has really thought about making development pleasant. Even the MCU names are extremely confusing. I'm currently using a STM32F303CCT6 MCU and the headers refer to this as STM32F303x6 and the datasheet refers to it as the STM32F303xC (and datasheet also has a part named STM32F303x6 but it is a different part).

Also often component cost is a fairly small factor in parts selection. Varying of course widely by industry and project volumes. But I do agree if you have any need for speed then ARM is the right choice. For many (if not most) microcontroller projects speed is a non-issue though.

Btw. I think SiLabs or someone had a very interesting "crowbar" remapping where you could almost without limitations remap peripherals to GPIO ports. That seemed pretty neat. The software support for that with GCC was non-existant at the time when I was looking in to it though.

[dannyf]

Should be spread around the chip to make for a cleaner layout.

It should be arbitrary - a perfect example is the remappable pin implementation on PIC24.

Btw. I think SiLabs or someone had a very interesting "crowbar" remapping where you could almost without limitations remap peripherals to GPIO ports.

aka PIC24F. I think some low-pin count LPC chips have that too.

In comparison, STM's remappable pin implementation is quite rudimentary.

[Jeroen3]

Some chips even go further, the LPC43xx series for example. It has P1_7, which corresponds to GPIO1[0] or P3_4 with GPIO1[14]. Good luck with that.
_{Remark: Note that the pin name is not indicative of the GPIO port assigned to it.}

However, question was a budget USB mcu.
You can either go sample some STM chips with usb, they provide USB examples and there are usb drivers available in chibios.
Or you can get an LPC11U24 or LPC1769 with the mbed USB libraries.
Or possibly some lesser known chips from Freescale or Cypress.
But if an 8 bit ATxmega can do your job, then you'll be just fine using that.
Remember Atmel prices contain Atmel studio development. STM/NXP prices do not contain the license to an IDE, you'll have to get it somewhere else.

[dannyf]

Remember Atmel prices contain Atmel studio development.

Atmel studio development = IDE (VS Express = free) + Compiler (gcc = free).

It is OK to pay for free things, but...

STM/NXP prices do not contain the license to an IDE,

STM: CooCox (Eclipse IDE + gcc), emIDE and emBlocks, ......

NXP: LPCXpress (Eclipse IDE + gcc).

Seems to be quite comparable to me, and as you suggested, they are truly free and none of the costs are baked in the chips. You seem to be making a great case FOR STM/NXP?

[Corporate666]

Probably but I would be surprised if those chips are still in material shipment 5 - 10 years from now.

Atmel has guaranteed availability for at least 15 years (or compatible parts, like the MEGA-P and PU series they did). If they decided to back out there would be huge legal liabilities. On top of that it would destroy their credibility in the industry. It just isn't going to happen.

Don't let the promises fool you.  I got screwed by Atmel on the same promises.  They came out with their super low cost MCU, I think it was the Tiny 11 at the time, and their selling point was $0.25/ea in reels... a remarkable price point that would let MCU's take over many jobs previously handled by analog or discrete logic chips.  We designed that ATTiny chip into a very cost sensitive product... within a few months, the original chip was discontinued, replaced by an upgraded model, I believe the ATTINY13 which had various improvements like ADC/EEPROM or whatever... none of which we needed.  The price was "upgraded" also, to $1.25 in reels.  A 500% jump.

Not long after (IIRC, less than a year), that chip was also discontinued and replaced by another "upgrade" in features.... and in price, to $1.50 in reels.  Presumably Atmel got a lot of backlash, because the prices came down, but it was not the first time Atmel did that.  They discontinue chips with alarming regularity and replace them with bigger (in features and price) chips. 

[Corporate666]

Yeah. I recommend the atxmegas mainly cause they just are so super nice to use.

They lost a lot of good will over the introduction of those controllers.

For a long time the xmegeas were not available at all, while Atmel was lying through their teeth and marketing them as available and buying themselves awards for those non-existing MCUs. Then the disastrous silicon errors when they were finally available. Accompanied with a new disastrous IDE, a disastrous library, and expensive new programmers required.

Many of the originally announced xmegas never shipped. Leaving people in the cold who trusted Atmel and started development on a smaller xmega or one missing a critical feature, believing they could soon get the right one.

Worst of all, Atmel refused to acknowledge the problems and to talk about them. The xmega disaster was what ultimately drove us away from Atmel. They lost all our trust.

Wow, your story mirrors mine almost exactly.

We were asked by a customer to develop a new product - an industrial tachometer, to be shown off in 6 months at an important industry trade show.  I was looking at Atmel's website and saw the much hyped XMega.  After talking with our FAE, he couldn't stop raving about how amazing the chip was and how it would be so easy to use, blah blah.  He assured me I could get samples immediately and lead time on reels would be 4-6 weeks or less... and that they were in mass production now, but the chip was soooo popular that they had a huge backlog of orders.

So we designed the chip into our product.  I distinctly remember that our samples were so delayed that I ended up buying a couple of eval boards from eBay (Atmel had given them away at some event and many ended up on eBay) and desoldering the chips from them to get some prototypes working.  And after pulling our hair out trying to get the project working, there was some bug in the ADC (don't recall the specifics this long after) that just made it non-working at all in our application.  Various folks at Atmel *promised* to high heaven that it was fixed in production silicon that would be available in mere weeks.

They never showed.  Ever.  We ended up cobbling together a totally hacked "prototype" of that product for the show that consisted of a Cypress dev board under the desk and a huge ribbon cable hacked onto the LED display of the product.

I distinctly remember getting the call from someone @ Atmel to let me know my samples had shipped - we had already scrapped the XMega idea and scrapped Atmel alltogether... and it was well over a YEAR from when we were first told that we could get a reel within a few weeks.

By that point, I had designed any Atmel chips out of any products that were in development, and since then we've designed them out of every product when we came up on redesigns.  Just like with you - Atmel just totally lost our trust.

That was not the only incident, but it was one of a few and it was by far the biggest.  I remember sitting in a large room filled with electronic design engineers getting a presentation from Atmel about some chip with built-in LCD control.  They had a slide with a BOM and costs... it had this $14 chip listed as "Less than $1".  When he got to that line, the room literally erupted in laughter.  The nordic guy giving the presentation got flustered and defensive at this and tried to sternly correct the audience that this was realistic pricing - which pissed off a few audience members who then took him to task on it.  He later admitted that this price was a special deal negotiated for one customer as a chip-on-board version in million-per-month quantities.  Everyone was laughing and guffawing at the excuses this guy was making about how these new chips were money savers and how they were going to be around to stay.

I realized that I wasn't the only victim of Atmel's pricing/availability/life-span business tactics.  A real eye-opener.  Not to mention the stack of ridiculous junk I spent a few grand on - STK600's with ridiculous adapters for various chips - Dragon's that had some flaw that caused them to burn out with regularity, and ISP programmers that died regularly (got a box full of dead versions of those).  Just crap, crap, crap.

[Vasi]

Very easy to breadboard and cheap.

But NOT "usb"; let's please stay on-topic, because once you branch out into "what's your favorite microprocessor" you never get anywhere.

XMEGA-wise, You can count me as one of the disappointed.   I don't think the smaller A-series chips (ATxmega64a4, for example) ever showed up for real.  (they didn't have USB either, so they're also off-topic.  The USB versions of the same chip were somewhat heralded as the first xMegas that were fully usable, IIRC, and people interested in a 64a4 were encouraged to just move on the 64a4u.)

SAM D21 - ATMEL advertise them as the next step for ATmega users (and maybe that is why there will be Arduino ZERO) and it came also in TQFP cases. What do you think?

[Kjelt]

In volume XMEGA is cheaper from Farnell:
ATXMEGA16A4U - £1.08 for 2000+
STM32F102C4T6A - £1.20 for 2000+

In those quantities I would call the factory distributor in your country and be amazed at what can be done if you order these regularly a complete reel at a time 

[nctnico]

Why would you use an XMega when you can have an STM32F10x or STM32F30x for essentially the same money? You can get a 32bit chip with a lot more power and hardware than 8bit XMega. Furthermore, you don't need to depend on Atmel-proprietary debuggers and programmers, any SWD or JTAG adaptor works with the ST chips.

Sorry, but these two platforms are not at all the same thing. Skimming the STM32F102x4 datasheet the current consumption is through the roof - 7mA at 8MHz, and a massive 32mA at 48MHz which still doesn't give you the I/O performance of an XMEGA at 32MHz which only needs 6mA. The 16K flash memory won't go nearly as far with ARM code either, and that 16K includes the bootloader where as on XMEGA you get an EXTRA 4k on top (so really the total memory size is 20k).

Someone mentioned "free compiler and IDE" - well, GCC works with every ARM in existence and Eclipse is just fine for an IDE, thank you very much. A lot of functionality works even better than in the Visual Studio (e.g. the Intellisense crap).

Atmel Studio comes with Visual Assist which is the best code completion tool ever. Seriously. It really does help improve code quality. Also GCC for ARM is fine, but what about debugging? Do you have source level stepping and real-time monitoring in the IDE?

Eclipse does all that. If you are used to Eclipse then having to use Visual Studio is like taking a cold shower when it is winter. IMHO the chips from ST are not the 'best' ARM chips you can get so make a poor comparison. For some reason they are popular because they are a few cents cheaper. NXP's ARM controllers consume less power. The LPC1111 for example consumes about 9mA when running at 48MHz.

[westfw]

SAM D21

Haven't you been listening?  The SAMD21 is a new Atmel product: its actual existence is not to be trusted until digikey and mouser both have had stock for "a while."  So far, the only D21 even in the catalog is the eval board...

(another Atmel horror story: remember the ATmega328p-pu shortage, where Atmel couldn't ship enough chips to keep a hobby board supplier supplied?)

[theatrus]

Sounds like we need a thread on "I've been burned by X" :-)   For the record, I too was burned by the xMega ADC and DAC problems (amazing spec sheet, never worked that well). Also burned by the Luminary/TI LM3 cancellation (though it had been years and was clear nothing was ever going to ship), and the Energy Micro (now SiLabs) Draco radio (slipped for years).

LUFA is bloated, but easy enough to understand. I have yet to make the jump over to ASF, but remembered finding some severe USB bugs back when I was using an AVR32 (!) in a project.

[Vasi]

(another Atmel horror story: remember the ATmega328p-pu shortage, where Atmel couldn't ship enough chips to keep a hobby board supplier supplied?)

I remember that one but, you know, I have an ASUS X202E laptop with an ATMEL chip for the touchscreen inside ...
And I'm hopping that now there are good times for ATMEL. Now ATmega/ATtiny series are fueling almost the entire Maker movement.

[Corporate666]

Strange, Mouser and Digikey bother still stock ATtiny models at those price ranges and pin compatible with the tiny11. Atmel usually only retire products when there is an easy migration path, often binary compatible. I'm not sure why you changed to vastly more expensive parts.

No, they don't.

Unless you consider more than double the price to be in the same price range.  And I'm not sure if you read my post, but the current pricing is about 1/3rd what it was a couple of years ago.

We changed to "vastly more expensive parts" because Atmel forced us to.  They came out with a part that was $0.25, then within the span of some months, it was discontinued, and Atmel's pin-compatible replacement was 500% more expensive.  Then that part was discontinued and replaced with another one that was about 20% more expensive still.  When I spoke to my FAE at Atmel about this, I just got bullshit excuses about how so many of their customers were just delighted with the new features of the ATTINY13 chips and felt the price was more than worth it. 

Bullshit.  There was a lot of complaining on AVRFreaks at the time.  Looks like their website is down, but the last post on this thread (Cached version) jives exactly with what the experienced.

http://webcache.googleusercontent.com/search?q=cache:IZxrkWolxm4J:www.avrfreaks.net/index.php%3Fname%3DPNphpBB2%26file%3Dprintview%26t%3D53596%26start%3D0+&cd=14&hl=en&ct=clnk&gl=us

Atmel loves to highlight their advantage as not being tied down with a bunch of legacy BS the same way Microchip is - but they discontinue parts with reckless abandon, and feel that a 500% more expensive replacement is acceptable.

Just to add some extra straw to the camel's back , we also had issues with ATTINY's "popcorning" - i.e. failing during the reflow process.  We had a few batches where the failure rate was around 30%.  When we talked to Atmel, they couldn't care less... "well, we adhere to JEDEC standards, so it's something you are doing wrong".  Except we were using a ridiculously expensive and process controlled reflow oven and were reflowing the boards within 30 minutes of when the reel was opened - a reel which had come directly from Atmel.  Only when cornered did they even agree to look at the chips, confirming they had popcorned and stating we must have done something wrong.  Strange that it was an issue for a few months and the problem disappeared as quickly as it started - all with chips from similar lot numbers. 

Contrast that with Cypress who decapped and analyzed chips for us when we experienced 3 failures out of a few thousand.  Atmel just doesn't give a shit.

[stevech]

I moved from AVRs to Teensy 3.1 ... because of value, small size, large memory, 32 bit, great library, great forum

http://www.pjrc.com/teensy/index.html
http://forum.pjrc.com/forum.php

[dannyf]

I moved from AVRs to Teensy 3.1

Paul is an upstanding guy. His bootloader is infinitely better than the arduino ones and the freescale chips are infinitely better than arduino arm offerings.

Arduino users are fool to migrate up without giving him a look.

[janoc]

Eclipse does all that. If you are used to Eclipse then having to use Visual Studio is like taking a cold shower when it is winter. IMHO the chips from ST are not the 'best' ARM chips you can get so make a poor comparison. For some reason they are popular because they are a few cents cheaper. NXP's ARM controllers consume less power. The LPC1111 for example consumes about 9mA when running at 48MHz.

Fully agree on Eclipse - the CDT plugin for C/C++ in Eclipse works a lot better for code editing than anything Visual Studio ever had, unless you want to buy a ton of plugins and extensions for Visual Studio.

The debugger in VS is decent, though - the one in Eclipse works only with gdb (problem when developing for Windows using MS compiler ). Most often I am writing code in Eclipse and running Visual Studio debugger in a second window on the side to debug. The only issue I have with Eclipse is that the configuration can be arcane (but have you seen the VS one?!) and that it can get sluggish at times (VS often just crashes outright though ...)

NXP chips are decent, I have been playing LPC17xx series, but they are a bit harder to get here. I need a one-offs and most distributors aren't too keen to deal with customers like me. ST is more widely available and a tad cheaper here too.

Let's not get into the discussion which ARM is the "best" ARM, that would be a worse flamewar than the eternal Atmel vs Microchip discussion 

[Kjelt]

Microchip is not a preferred supplier with my company since they *&*&^* up a couple of years ago.
We designed a uC of them in a mass product but when the production started after a year of R&D en pre-dev they couldn't deliver the amounts necessary.
The factory was ready to go , PCBs and all components ordered but from the I believe around 1 million uC's ordered we got 150000  (15%) and they told us we should wait till next quarter for the next batch (also probably 150000).
It was game over for them at that moment, we redesigned the product, had to do all the retesting again, huge write off.
They might be better now but in the past they had logistical issues to deliver huge quantities. So if you are designing and need huge quantities better make a good contract with them with a huge penalty for not delivering on time, that's the only way to deal with it.

[dannyf]

around 1 million uC's ordered we got 150000

Their issue is that they have too broad of a portfolio so the demand for each chip doesn't allow large scale production. So when a big order comes, they are unprepared for that.

I think it would have been a lot better to produce a feature rich chip and sell it at a lower mark-up so it covers a larger set of applications. The economy of scale would work better in that case for them.

[Kjelt]

Their issue is that they have too broad of a portfolio so the demand for each chip doesn't allow large scale production. So when a big order comes, they are unprepared for that.

A company as ST also has a broad portfolio but has no problem with those numbers of uC's 

[dannyf]

ST's microcontroller portfolio is probably less than 50% of Microchip's, if not 10% of microchip's.

Not to mention that ST is a far bigger company overall.

[Kjelt]

ST's microcontroller portfolio is probably less than 50% of Microchip's, if not 10% of microchip's.

I didn't know that, seeing all the different packages and types ST sells ..........

Not to mention that ST is a far bigger company overall.

Well that is the whole point isn't it?

[dannyf]

OK.

For mcu offerings:

digikey: 13000 microchip vs. 2000 st;
mouser: 9500 microchip vs. 1200 st;
avnet: 12000 microchip vs. 2300 st.
...

Now, it is not scientific and quite flawed but generally points you in the right direction.

Microchip's advantage is its huge installed base.

Unfortunately, its disadvantage is also its huge installed base.

Well that is the whole point isn't it?

Yeah -> a smaller company + a more diversified portfolio -> even less economy of scale.

[Kjelt]

Microchip's advantage is its huge installed base.
Unfortunately, its disadvantage is also its huge installed base. 

Must be the quote of the day