Is it normal to brick the STM32F0 with certain software pin configurations?

Question

I've flashed the following code to my shiny new STM32F0DISCOVERY board. The comments explain what I thought it would do.

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
    // Place PIN 4 (DAC out) into analog mode
GPIOA->MODER=0b11<<8;

RCC_AHBPeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
// Default DAC settings are fine.
DAC->CR = 0;
DAC->CR = 1;

Unfortunately after flashing this code openocd can no longer talk to the board or recognize that it is an stm32f0 (but it can still connect to the onboard ST/LINK if the reset button is held down). I thought I might be able to hold BOOT0 high and boot from the internal serial bootloader, but that doesn't seem to allow SWD flashing either. The rest of the short program just uses GPIO B and C and the timer.

Should I expect that code to brick the chip or did I just get unlucky?

Answer 1

For whatever reason openocd was no longer able to talk to the device after flashing the code. Thankfully the official Windows ST/LINK tool was able to erase the chip with the "connect under reset" option.

Answer 2

Just for other readers who don't have a STM32F*DISCOVERY board: All STM32 have bootloaders which can be used to program the chip as well. You will have to set the BOOT pin(s) accordingly to boot from "System Memory" and connect the appropriate serial peripheral (See: "AN2606 STM32 microcontroller system memory boot mode" http://www.st.com/web/en/resource/technical/document/application_note/CD00167594.pdf). The bootloader will work even when the JTAG or SWD pins are overwritten in software or the clock has ben misconfigured preventing normal boot up. One such tool for flashing that runs on linux would be http://code.google.com/p/stm32flash.