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Honest STM32F103C based Dev Boards
#1
Some time ago I decided to get some STM32F103C boards, aka Blue Pills. I ordered 5 of them from a chinese seller. The boards were comparatively priced as many others, around $2.50USD. The caveat was that I needed to wait almost 2 months before I got them. No big issue as being in the US, we know we order and then wait a long time. That was expected. 

Well, once I got the boards, I proceeded to go through the steps of setting them up so I can use them with the Arduino IDE. The first one was having issues, so I tried another one. Same issue. I figured I must of been doing something wrong, so I reached out to the guys as stm32duino.com forum to get some professional help. In the end, it was ruled I had dud ICs. I had tried all 5 of the boards, and all were duds. I even sent one to rev0 to get a second opinion, and he came back with the same result: "They were dead, Jim". Another thing that was noted, is that the ICs on the boards I had gotten were 32k flash. They were supposed to be 64k. According to the datahsheet, 64k and 128k are the flash sizes for the STM32F103Cx based boards.

I looked around on eBay for the boards in the US market, as I didn't want to wait almost 2 months get anymore boards. The price in the US is twice anywhere else, and several sellers tacked on shipping too. So I decided to look into building my own board. I did a BOM and the parts were cheaper than what they were on eBay. Granted, I needed to build these boards before they were functional, but it was a start. I know time is money, but time can also *save* you money, too. If you don't do something valuable with your time, then it's just wasted, right?

So I decided to see about designing the board layout, and I fired up EasyEDA and looked at the schematic from stm32duino.com on the STM32F103C boards. Then designed the layout based on the schematics. This took about 4 hours in total. I've gotten a lot better with the designer since I first started with EasyEDA. 
The pcbs and the parts will come from JLPCB and LCSC respectively. So I know the pcbs and the components are legit and good quality. The SMT32F103Cx ICs will be as they are supposed to be. No fakes

I figured that I could make these boards and sell them to the US market with better quality parts, and faster shipping (because even the "US" labeled stores are sometimes not really in the US (shocker!)) than the other stores. The first batch will be the basic STM32F103C8T6 ICs, 

* 64k flash
* 20k sram
* 2 SPI
* 2 I2C
* 3 USART
* 1 USB
* 1 CAN
* 37 GPIOs
* 2 10-bit ADCs
* 72 Mhz CPU
* 2.0V - 3.6V operating range
* -40C - 85C operating temperature range


Future versions will have the option to have the 128K flash and/or one of the other ICs for the STM32F103x family. This can give up to 2x 16-bit ADCs & 80 GPIOs.

I have started a KickStarter Campaign. Please feel free to ask any questions, or add suggestions. 

https://www.kickstarter.com/projects/kor...ref=f243s2

No More Fake MCUs!
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#2
Here's a current view of the PCB Layout:



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#3
Is there any way (visually) to tell if you have a fake or not?

Also apparently some of the Chinese copies have an incorrect pull up resistor on the USB port. The other thing is apparently the 5v-3.3v voltage regulator is a little under-powered on some, and when overloaded goes short circuit - frying the microcontroller.

All of this I found, but not a lot of helpful information about the counterfeit microcontroller.
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#4
(02-14-2019, 05:41 AM)Geek Wrote: Is there any way (visually) to tell if you have a fake or not?

I'm afraid not. I think what the "fake" ICs are are really rejects that didn't pass the quality check. The only way to really know is to use STM's firmware flashing program as it reads the data from the IC and tells you what the flash size is. And even that may not "always" be accurate. You have to flash it with some firmwares to see if they take.
I even broke out the large magnifying lens and light to see if I could tell if there was any difference on the ICs label, and there's not. rev0 sent me a working/legit board I could use as a reference and you can't visually tell the difference between the two mcu's. They are even the same height, so the chances of them having the tops sanded and re-etches is pretty slim. Unless they can sand off 100ths of a mm that I can't detect with standard tools.

The ones I had gotten did have a working firmware on it. When powered up, they would run 'some kind' of led blink program. But when flashing it with 'any' other firmware, it'd crash. And unfortunately, you can't really reverse engineer a compiled firmware. At least I can't, and doubt it would do any good even if you could.

(02-14-2019, 05:41 AM)Geek Wrote: Also apparently some of the Chinese copies have an incorrect pull up resistor on the USB port. The other thing is apparently the 5v-3.3v voltage regulator is a little under-powered on some, and when overloaded goes short circuit - frying the microcontroller.

Yes, that's the other issue with them, too. But this only effects them if you try to do anything on the USB side. This is a mute point if you flash using the FTDI or ST-Link interfaces.

rev0 brought it to my attention about the regulator, too. So the one I'll be using is a better version. The RT9193 (Datasheet) is the regulator I'll be using, currently. rev0 suggested another one that I might use as well. This one is a 300mA regulator, and the one he suggested I think can do 500mA.

This is why the first batch of boards are testing boards to make sure we get good ones and upgrade to needed parts for future boards, and why I'm only limiting to 100 boards to start with.

The parts will be coming from LCSC, so every part 'should' be fully legit components w/o any short cuts pulled. No parts will be eBay/AliExpress/AliBaba/etc specials. No shortcuts, no compromises.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#5
Are you buying the stencil? Have you thought about 3d printing the stencil? I've seen that work well for other people.
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#6
I'll get the stencil from JLCPCB. It only costs about $9USD if I remember correctly. And I'll make sure it has several boards on it so I can do multiple pastes at once.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#7
Update:
Made the $500 goal!!! WOOOO!!!!!   Thanks to any of you who helped.

Now the hard part of soldering all those tiny pieces to the pcb  Tongue

Here's a history of the revisions:

The 2nd and 3rd are almost identical except for some label size adjustments, trace adjustments, and added vias
The 3rd one has many vias to give as much GND plane as possible. Almost the entire board top/bottom is covered with copper now.
Church1182 likes this post
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#8
Congratulations. That was quick!
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#9
Yeah, I wasn't expecting to go from $0 to $500 in 9 days Tongue There are some people who "really" want these boards! 1 guy is requesting 100 boards alone. It took me a moment to process that request mentally and re-read the comment a few times to make sure I read it right Tongue
Proceed with caution. Knowledge is Power! Literally! Cool 
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#10
Awesome man, thanks for putting in the work to do this. It's kinda amazing how hard it is to get something that isn't total crap these days. Not sure if anyone said this, but although hot air rework stuff is cool, for making the boards you really want an oven - it's waaay easier (just pop it in and go) vs manually using a hot air station. Also, hot air has some other issues. But looks cool man!
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