Independent Watchdog when debugger is connected

peterhug9 · ‎2008-08-13

Posted on August 13, 2008 at 14:21

peterhug9 · ‎2011-05-17

Posted on May 17, 2011 at 12:20

I'm experiencing a confusing observation. When the debugger with j-link (IAR) is connected to the development board (STM32-SK from IAR) the watchdog does not reset the board.

The only reaction of the mcu is that the bit IWDGRSTF in the register RCC_CSR changes to 1 indicating a reset due to the watchdog had occurred. But it didn't.

When I look into the documentation there is also a bit DBG_IWDG_STOP in the register DBG_MCU_CR which can be used to control if the watchdog should continue to run (or not) even if the core is halted. I set this bit to 0 so the watchdog should continue to run.

The only configuration I see the watchdog working is when I disconnect j-link and run the code from flash.

16-32micros · ‎2011-05-17

Posted on May 17, 2011 at 12:20

Hi Peter,

I have tested the same on my SK-Board, When enabling the IWDG (Reset after 500msec for example with HSI, when counter not reloaded in a while loop): the MCU does not reset.

--> This behavior is due to the RT jumper ( soldered in the bottom side of he STM32-SK board. In fact this jumper is fitted ( soldered) by default and we can not remove it easily. So the pin 3 of JTAG is connected to both pin NRST and JTRST of the chip. So when the IWDG generates a reset, it will reset also the JTAG TAP and in this case it does not work well.

This problem disappears when:

- Using the SWD (because this pin 3 is not used by J-Link)

- The J-link is not connected.

I suggest you to rework the board with a simple de-soldering tool, it is very easy.

Please let me if it helps. Cheers,

STOne-32.