Hey Everybody,

I'm running in to a halting error on my olimex STM32 dev board that I do not understand and I'd like to solicit eyes and advice for debugging it.


I've migrated the bits of the old si project related to reading data from the MPU9150 sensor over to my eventlogger project, in the 'eventlog-sensor' branch of psas/stm32 on github. I've rearranged things by putting the MPU9150 functions in their own c file, rather than just throwing everything in main, but I (as far as I can tell) have not functionally changed anything.

It does all work... for a little while, at least, until the system just halts. It usually halts after roughly 900 reads of the sensor data, but sometimes it'll go for 1200 or 1800 interrupts before halting. I have not been able to determine why the number changes; sometimes the number will change between resets, without re-programming the device!

It seems that the problem lies in the Thread_mpu9150_int_dispatch, since if I do not start that thread then the system does not halt. That thread does very little: it loops forever waiting for the mpu9150_int_event to be broadcast, and when it is it calls the mpu9150_int_event_handler function to actually read the data. I am unsure what in either of these two functions could be causing the halt, since they appear to be functionally identical to the versions in the si project that do not halt.

At first I suspected stack space exhaustion, but increasing the amount of stack space, even by eight times (up to 4KB) does not help (indeed, it seems to _decrease_ the time that it runs before halting). Turning off MPU9150_DEBUG so that nothing gets printed doesn't fix things, nor even noticeably increase runtime before halt.

Is there any way to determine the cause of a halt? I've heard that it is possible to wrangle gdb into stepping through the program on the STM32; are there any writeups of how to do this? Can anyone else spot a difference between the mpu9150-related portions of si and eventlogger that would explain this halting?

Cheers,
-Dan

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