stm32tips.md

stm32 tips

• build and debug flags
• different behavior on debugging versus upload
• Error erasing flash with vFlashErase packet error
• stm32f446re : Serial3 and Serial4 conflicts
• troubleshoot
  • libusb_open() failed with LIBUSB_ERROR_ACCESS

build and debug flags

• to avoid forgetting to return value on function declaring a return type; this will block the process ( it may be for a disaligned heap )

build_flags = 
	-Werror=return-type

• to enable debug doesn't optimize variables

debug_build_flags = -O0 -g -ggdb

different behavior on debugging versus upload

• double check if you call functions that promise to return something but lacks of a return statement

bool SomeFn()
{
// missing return
}

Error erasing flash with vFlashErase packet error

• close all vscode
• ps ax | grep -i platform : then kill platformio processes
• ps ax | grep -i openocd : then kill openocd processes
• detach/reattach usb

stm32f446re : Serial3 and Serial4 conflicts

configuring Serial3 with PC11(rx) and PC10(tx) and Serial4 with PA1(rx) and PA0(tx) youll'get a strange behavior: writing to Serial3 results in receive to Serial4. Effectively this relates to ALTERNATE FUNCTIONS of pins.

to use all serials in f446re, supply platformio.ini with follow config ( Serial2 is attached the usb ) :

	-DENABLE_HWSERIAL1 -DPIN_SERIAL1_RX=PB7 -DPIN_SERIAL1_TX=PA9
	-DENABLE_HWSERIAL3 -DPIN_SERIAL3_RX=PC11_ALT1 -DPIN_SERIAL3_TX=PC10_ALT1	
	-DENABLE_HWSERIAL4 -DPIN_SERIAL4_RX=PA1 -DPIN_SERIAL4_TX=PA0
	-DENABLE_HWSERIAL5 -DPIN_SERIAL5_RX=PD2 -DPIN_SERIAL5_TX=PC12	
	-DENABLE_HWSERIAL6 -DPIN_SERIAL6_RX=PC7 -DPIN_SERIAL6_TX=PC6

troubleshoot

libusb_open() failed with LIBUSB_ERROR_ACCESS

apt install stlink-tools
systemctl restart udev

then reconnect device