STM32F103C8T6 ARM STM32 Minimum System Development Board

August 28, 2020

Getting Started

I first started working with these back in 2016. I haven't touched one in 3 years and am now getting busy with them again. I have forgotten a lot of what I learned 3 years ago! So this seems like a great time to explain to someone how to get started with one of these.

I will call this "the STM32" in what follows, since calling it "the STM32F103C8T6 ARM STM32 Minimum System Development Board" quickly becomes tedious. I may also call it the "blue pill".

Buy some of these, and a couple of ST-Link V2 gadgets

Get on AliExpress and order 10 of them. Why not? They are less than $2 (in 2020) or maybe $3 (in 2022). The best deal I could find in December of 2022 was a package of 10 for $27.50 and $1.05 shipping (so $2.81 each). You can have all kinds of fun with them. Also order several ST-Link V2 gadgets for $5 each. (The best deal I found in December of 2022 was $3.82 including shipping). Order at least two so you have a spare. Now wait 2 weeks until the packages arrive from China. If you aren't that patient, look on Ebay or even Amazon.

While you are at it, buy a half dozen CP2102 or CP2104 USB to serial devices. These usually cost about $1.00 and will be useful and necessary when you want a serial console.

Grab some scissors and open the bag

Mine always show up in a sealed anti-static bag along with the header pins you will probably want eventually. What a bargain!

Check that both jumpers are on "0" and leave them there. Forever!

Now just for fun, scrounge up a micro USB cable and plug it in. This is only to supply power and see what happens. Mine lights up the Red LED (which is a power LED) and starts blinking the green LED. But on some of my older units, it is the other way around, the green LED lights up (and it is the power LED) and the red LED starts blinking. So it shipped with some kind of blink demo installed. This can be good or bad. Sometimes they load the blink demo and also blow a security fuse. If so it is a hassle, but we are getting ahead of ourselves.

USB

I have never yet used USB for anything (other than powering the unit). If you are used to something like the ESP8266 NodeMCU modules where USB supplies a console, forget it. You can get a console, but not that way. We will get to that. This is not to say that the USB is useless, it is actually a very cool part of the STM32, but is not part of getting started with it.

Grab the ST-Link V2 gadget

I should note that this is how I like to do things. An alternative way is to use some kind of boot loader (which you have to burn into the unit somehow) and perhaps even the Arduino IDE. I have no interest in any of that. I use Makefiles, a C compiler, and do what many people call "bare metal" programming. To each his own. It takes all kinds to make a world.

The ST-Link has a USB connector on one end, and 10 pins on the other end. We are going to use 4 of those 10 pins to connect to the 4 pins on the end of the STM32 opposite the USB connector. The ST-Link usually comes with a little cable, but if not you will have to scrounge up a 4 conductor cable, female on each end. You want to connect SWCLK, SWDIO, Ground, and 3.3 volts. They are NOT in the same order on each device, so pay attention and get this right. I also avoid having the ST-Link and a USB cable both connected, that would power the device from both USB and from the ST-Link, and might not be good.

Install openocd and the cross compiler

I am running Fedora linux and this is an available package, so I just do: 
dnf install openocd
Installing the cross compiler and toolchain is equally easy: 
dnf install arm-none-eabi-gcc-cs

(1/2): arm-none-eabi-binutils-cs-2.25-3.fc24.x86_64.rpm
(2/2): arm-none-eabi-gcc-cs-5.2.0-4.fc24.x86_64.rpm

Fetch one of my examples

I have put a bunch of my stuff on Github, so do: 
git clone https://github.com/trebisky/stm32f103.git

Try one of my blink demos

Plug the ST-Link into a USB "jack" on your computer. The power LED should come on, and the blink demo should still run. Then do this: 
cd stm32f103/blink2
make
make flash
When I did this on some recently purchased units, I ran into trouble. See my "problems" section.

When I do this on one of my old reliable units, I see the following: 

make flash
openocd -f /usr/share/openocd/scripts/interface/stlink-v2.cfg -f /usr/share/openocd/scripts/target/stm32f1x.cfg -c "program blink.elf verify reset exit"
Open On-Chip Debugger 0.10.0
Licensed under GNU GPL v2
For bug reports, read
	http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport "hla_swd". To override use 'transport select '.
Info : The selected transport took over low-level target control. The results might differ compared to plain JTAG/SWD
adapter speed: 1000 kHz
adapter_nsrst_delay: 100
none separate
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : Unable to match requested speed 1000 kHz, using 950 kHz
Info : clock speed 950 kHz
Info : STLINK v2 JTAG v21 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : using stlink api v2
Info : Target voltage: 3.182505
Info : stm32f1x.cpu: hardware has 6 breakpoints, 4 watchpoints
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x08000052 msp: 0x20005000
** Programming Started **
auto erase enabled
Info : device id = 0x20036410
Info : flash size = 64kbytes
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x2000003a msp: 0x20005000
wrote 1024 bytes from file blink.elf in 0.098073s (10.196 KiB/s)
** Programming Finished **
** Verify Started **
target halted due to breakpoint, current mode: Thread
xPSR: 0x61000000 pc: 0x2000002e msp: 0x20005000
verified 352 bytes in 0.022623s (15.195 KiB/s)
** Verified OK **
** Resetting Target **
shutdown command invoked
And my blink2 demo is flashing away. It blinks 3 times, then there is a longer pause. This allows you to distinguish it from the blink demo that is sometimes shipped in the unit.

Problems

You may be shipped devices with a security fuse blown. This is a pain in the ass, but the unit can be reset.

Also there are reports of different kinds of chips being installed in what look like the same old "blue pill".

I have another page elsewhere that discusses both of these issues.

Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org