STM32

STM32 programming

Boot mode configuration

BOOT1 BOOT0 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

STM32F103C86T dev board boot pins

• https://www.aliexpress.com/item/Free-Shipping-STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-Forarduino/32525208361.html
• http://www.ebay.com/itm/STM32F103C8T6-ARM-STM32-Minimum-System-Development-Board-Module-For-Arduino-DHUS-/321569700934?pt=LH_DefaultDomain_0&hash=item4adf0c3c46

Legend

 o o o BOOT0
 o o o BOOT1
 ---
 |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.

arm-none-eabi-objcopy -O binary miniblink.elf miniblink.bin

Using stm32flash

Test connection with

stm32flash /dev/ttyUSB0

Flash and run from 0x0

stm32flash /dev/ttyUSB0 -w miniblink.bin -g 0x0

Pinout

Libraries

libopencm3

Minimalistic firmware library/framework.

Bootstrapping on Fedora

Library

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 ..

DFU bootloader

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

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

Sample application

For use with DFU bootloader (stm32/f1).

git clone https://git.48.io/libopencm3_template
cd libopencm3_template
# flash via dfu
make dfu
# or with JTAG
make flash

Library examples

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

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

Info : Device Security Bit Set
stm32x unlocked

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

openocd -f jlink_swd_f103.cfg
telnet 127.0.0.1 4444
# in telnet issue:
stm32f1x unlock 0

Debugging

• https://github.com/blacksphere/blackmagic/wiki/Useful-GDB-commands

Debugging hardware

• JLink
• Flyswatter
• Black Magic Probe
• ST-Link clones

ST-Link clones or Discovery boards are flashable with Black Magic Probe firmware.

JLink

# 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'

Black Magic probe

• https://github.com/blacksphere/blackmagic/wiki

Running BMP on Discovery boards

• http://embdev.net/articles/STM_Discovery_as_Black_Magic_Probe
• https://esden.net/2014/12/29/black-magic-discovery/

F3 Discovery

Shorting solder bridges SB13 and SB15 connects UART1 port from STM32F303 to STM32F103 making it possible to use Black Magic Probe as UART bridge via /dev/ttyACM1

F4 Discovery

To enable UART bridge via BMP on older F4 discovery (STM32F407) you need to solder wires between UART2 (PA2/PA3) on STM32F407 to pins PA2/PA3 on STM32F103. These are located in the corners of the chips. Take care when soldering PA3 on F407 as it's positioned near VSS, if you manage to short these pins try lifting PA3 from the pad completely soldering wire directly to it.

Flashing

# make PROBE_HOST=stlink
# flashing blackmagic_dfu via black magic probe
arm-none-eabi-gdb --ex 'target extended-remote /dev/ttyACM0' blackmagic_dfu
monitor swdp_scan
attach 1
monitor option erase
# restart target so it unlocks, repeat up to 'monitor option erase' then issue
load
# restart target, it should boot to black magic dfu
# [  +0.000002] usb 1-1.2: Product: Black Magic (Upgrade) for STLink/Discovery, (Firmware v1.6-rc0-257-gd6e2977)
# upload black magic via dfu
dfu-util -s 0x08002000:leave -D blackmagic.bin

Usage

arm-none-eabi-gdb --ex 'target extended-remote /dev/ttyACM0'
# Use following commands when in gdb
monitor swdp_scan
attach 1

Sample session:

(gdb) monitor swdp_scan
Target voltage: unknown
Available Targets:
No. Att Driver
1      STM32F4xx
(gdb) attach 1
Attaching to Remote target
Error while running hook_stop:
Invalid type combination in equality test.
0x080035c2 in ?? ()
(gdb) bt
#0  0x080035c2 in ?? ()
#1  0x08001032 in ?? ()
#2  0x08001032 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

To access serial bridge:

screen /dev/ttyACM1 115200

Links

DMA

• http://jeelabs.org/article/1610c/

DAC

• http://embedded-lab.com/blog/stm32-digital-analogue-converter-dac/

Docs

• STM32 F3 Discovery (STM32F303VC) Manual
• STM32 F4 Discovery (STM32F407VG) Manual
• STM32F303VC
• STM32F407
• STM32F334
• Getting started with STM32F3 series
• Migrating from F1 to F3 series

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