Add documentation for firmware upload with stm32flash

1 files changed, 33 insertions, 0 deletions

diff --git a/firmware/README.txt b/firmware/README.txt
index d24eab5..7836bc2 100644
--- a/firmware/README.txt
+++ b/firmware/README.txt
@@ -43,6 +43,39 @@ Mention that you do not have to quit GDB to upload new compiled firmware. Just
 call `load` and `run` again.
 
 
+Upload firmware via serial bootloader
+-------------------------------------
+
+STM32 microcontrollers have a built-in serial bootloader to flash firmware. It
+is activated if pin BOOT0 is pulled to 3.3 V, BOOT1 to 0 V (GND) and the
+microcontroller is restarted. In this state it is possible to flash firmware
+with just a USB to serial adapter via USART1 (PA9 and PA10). This works with a
+FTDI USB to UART adapter (3.3 V TTL logic and 5 V VCC).
+
+To upload a *.bin firmware to the MCU just follow these steps. You will need to
+install the stm32flash utility (maybe via AUR):
+
+- connect:
+	- GND (UART adapter) to GND (MCU)
+	- RX (UART adapter, yellow in my case) to PA9 (MCU)
+	- TX (UART adapter, orange in my case) to PA10 (MCU)
+	- VCC (UART adapter) to VCC (MCU) just if no other power source is
+	  connected!
+- set BOOT0 to 1 (3.3 V) and BOOT1 to 0 (GND)
+- reboot MCU
+- flash firmware with stm32flash
+
+To flash and verify `firmware.bin` via `/dev/ttyUSB0` use this command:
+
+	stm32flash -w firmware.bin -v /dev/ttyUSB0
+
+It can then be started with:
+
+	stm32flash -g 0x0 /dev/ttyUSB0
+
+For further details run `man stm32flash`.
+
+
 External References
 -------------------