We Have a Fixed Firmware!

A project log for Motor Shield Reprogramming

Create and flash new firmware for the WeMos D1 Mini Motor Shield.

þeshipuþeshipu 04/21/2017 at 17:215 Comments

@Piotr Bugalski has recently re-written the firmware for this motor shield, and published it at From what I can tell, the new firmware is compatible with the old one, minus the hanging and crashing, so it should be perfect for a drop-in replacement.

Here is how you can flash it to your shield:

Solder two wires to the first two legs of the microcontroller, counting from the top, like this:

Be careful to not short them with the legs next to them. This is probably the hardest part.

Next, connect you ST-Link programmer as follows:

SWCLK ↔ first wire

SWDIO ↔ second wire


3V3 ↔ 3V3


Note that, this is with the shiled *not* connected to the D1 Mini.

Now, clone the repository:

$ git clone
$ cd wemos_motor_shield

Make sure you have installed openocd and arm-none-eabi-gcc. Compile the firmware:

$ make
arm-none-eabi-gcc -Wall -g -std=c99 -Os -mlittle-endian -mcpu=cortex-m0 -march=armv6-m -mthumb -ffunction-sections -fdata-sections -Wl,--gc-sections -Wl, -Iinc src/startup_stm32.s src/main.c src/user_i2c.c src/tb6612.c -o motor_shield.elf -Tstm32f030.ld
arm-none-eabi-objcopy -O binary motor_shield.elf motor_shield.bin
arm-none-eabi-size motor_shield.elf
   text	   data	    bss	    dec	    hex	filename
   2032	   1084	   1056	   4172	   104c	motor_shield.elf

And flash it onto the shield:

$ make program
openocd -f stm32f0motor.cfg -f stm32f0-openocd.cfg -c "stm_flash motor_shield.bin" -c shutdown
Open On-Chip Debugger 0.9.0 (2015-09-02-10:42)
Licensed under GNU GPL v2
For bug reports, read
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
srst_only separate srst_nogate srst_open_drain connect_deassert_srst
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 v17 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : using stlink api v2
Info : Target voltage: 3.490340
Info : stm32f0x.cpu: hardware has 4 breakpoints, 2 watchpoints
target state: halted
target halted due to debug-request, current mode: Thread 
xPSR: 0xc1000000 pc: 0xfffffffe msp: 0xfffffffc
auto erase enabled
Info : device id = 0x10006444
Info : flash size = 16kbytes
target state: halted
target halted due to breakpoint, current mode: Thread 
xPSR: 0x61000000 pc: 0x2000003a msp: 0xfffffffc
wrote 4096 bytes from file motor_shield.bin in 0.287988s (13.889 KiB/s)
target state: halted
target halted due to breakpoint, current mode: Thread 
xPSR: 0x61000000 pc: 0x2000002e msp: 0xfffffffc
verified 3116 bytes in 0.057512s (52.910 KiB/s)
shutdown command invoked
Now, disconnect everything. Your board has the new firmware on it. You can test it, and then desolder the two wires -- you won't be needing them anymore.


daveh wrote 06/14/2017 at 20:19 point

I needed an extra step, as my motor shield was locked. So, in order to flash I needed to issue a "stm32f1x unlock 0" to unlock, power cycle, then I could 'make program'

P.S. I also had a problem with the reset pin, but adding "reset_config none separate" to the start of stm32f0-openocd.cfg solved that.

Oh, and by the way, the serial method didn't work for me. Probably because the firmware was locked. 

  Are you sure? yes | no

þeshipu wrote 06/14/2017 at 20:25 point

That is weird, it did work for me on a locked shield. In fact, the first two commands are supposed to unlock it.

  Are you sure? yes | no

þeshipu wrote 06/14/2017 at 20:39 point

Say, does the serial programming work once you have unlocked it? Can you check?

  Are you sure? yes | no

daveh wrote 06/15/2017 at 13:58 point

Serial programming does not work for me before or after unlocking. I also tried various combinations of '-m' with a 3.3v FTDI cable.

I'm absolutely delighted to have that new firmware though! Thanks. I might get some pogo-pins or something to make the process easier though, soldering to those tiny pins is a bit of a pain. 

  Are you sure? yes | no

þeshipu wrote 06/15/2017 at 14:06 point

That's weird. Are you sure you shorted the RTS pin to 3V3?

  Are you sure? yes | no