STM32 programming

Boot mode configuration

<syntaxhighlight lang="bash">BOOT0 BOOT1 Boot mode Address

 x     0   Main Flash memory                      0x8000000
 0     1   System memory (built-in bootloader)    0x1FFFB000
 1     1   Embedded SRAM                          0x20000000

 in Main flash memory and System memory boot modes address is aliased to 0x0</syntaxhighlight>

STM32F103C86T dev board boot pins

Legend

 o o o BOOT1
 o o o BOOT0
 ---
 |R|   Reset button
 ---

Boot to bootloader (built-in bootloader)

Allows flashing over USART

 o [=]
 [=] o
 ---
 |R|
 ---

Boot to main flash (user code)

 [=] o
 o o o
 ---
 |R|
 ---

Flashing

Flashing is done via USART1 (A9 TX A10 RX)

Converting Elf to Bin

Required if you only have elf files produced by your toolchain - stm32flash accepts only *.bin files.

<syntaxhighlight lang="bash"> arm-none-eabi-objcopy -O binary miniblink.elf miniblink.bin </syntaxhighlight>

Using stm32flash

Test connection with

<syntaxhighlight lang="bash"> stm32flash /dev/ttyUSB0 </syntaxhighlight>

Flash and run from 0x0

<syntaxhighlight lang="bash"> stm32flash /dev/ttyUSB0 -w miniblink.bin -g 0x0 </syntaxhighlight>

Pinout

Libraries

libopencm3

Minimalistic firmware library/framework.

Bootstrapping on Fedora

Library

<syntaxhighlight lang="bash">dnf install arm-none-eabi* mkdir embedded git clone https://github.com/libopencm3/libopencm3 cd libopencm3

Edit TARGETS in Makefile and keep only targets that you need (or just stm32/f1 for example).

make -j8 cd ..</syntaxhighlight>

DFU bootloader

This is a bootloader for Device Firmware Update via USB (stm32/f1).

<syntaxhighlight lang="bash">git clone https://git.48.io/libopencm3_dfu cd libopencm3_dfu

connect JTAG

make flash

or flash via USART & stm32flash, see flashing section above

make stm32flash</syntaxhighlight>

Sample application

For use with DFU bootloader (stm32/f1).

<syntaxhighlight lang="bash">git clone https://git.48.io/libopencm3_template cd libopencm3_template

flash via dfu

make dfu

or with JTAG

make flash</syntaxhighlight>

Library examples

<syntaxhighlight lang="bash">git clone https://github.com/libopencm3/libopencm3-examples

Either fetch git submodule pointing to libopencm3 and repeat steps in Library section
or symlink libopecm3 dir to previously built libopencm3

cd libopencm3-examples rmdir libopencm3 ln -s <PATH_TO-->/libopencm3 .

try building miniblink example

cd examples/stm32/f1/stm32-h103/miniblink make</syntaxhighlight>

Troubleshooting

use make V=1 when make fails
make sure openocd is not running when doing 'make flash'

Locked device

If you can't flash and 'make V=1 flash' reports something similar

<syntaxhighlight lang="bash">Info : Device Security Bit Set stm32x unlocked</syntaxhighlight>

You need to unlock your device first (with JTAG):

<syntaxhighlight lang="bash">openocd -f jlink_swd_f103.cfg telnet 127.0.0.1 4444

in telnet issue:

stm32f1x unlock 0</syntaxhighlight>

Debugging

<syntaxhighlight lang="bash"># add to Makefile to generate debuginfo CXXFLAGS = -g

run openocd

openocd -f jlink_swd_f103.cfg

connect to openocd via gdb

arm-none-eabi-gdb --ex 'target remote localhost:3333' <EXECUTABLE>.elf

Use following commands when in gdb (more at http://www.yolinux.com/TUTORIALS/GDB-Commands.html)
c (continue), stop execution with Ctrl-C
bt (stacktrace)
b (break), e.g. 'b main' or 'b template.c:360'</syntaxhighlight>

Calculating Timer Frequency

MUCH WIP

period_target_ms = p1 period_hz = p2

1000ms / p1 = p2

E.g. for 20ms (servo) period

1000ms / 20 ms = 50 hz

cpu_freq = 72Mhz prescale = 72

72MHz / 72 = 1Mhz

This increases out count register CNT by 1 000 000 each second. To calculate what is the correct value for the ARR register (which defines the period), we divide the result of the prescaled frequency by the intended frequency for our period:

1 000 000 Hz / 50 Hz = 20 000

Now every time the CNT register is increased by one, this is the equivalent to 1us. The duty cycle now could by set easily. E.g. for a 1.5ms duty cycle we set the CCRx register to 1500.

Stepper

driver_max_duty = 250khz

From http://www.kaltpost.de/?page_id=412