HAL_CAN_GetTxMailboxesFreeLevel does not work with debug

[matheuscaltran]

hi, I'm using a discovery stm32f429 together with the STM32CubeIDE

I would like to know why when I use while to wait for the mailbox:

while (HAL_CAN_GetTxMailboxesFreeLevel(&hcan1) != 3)
{
// Wait until all transmission buffers are free
}

the debug does not work and gives an error:

Failed to assign value 8000c69, to register 0
Failed to assign value 20000028, to register 0
Failed to assign value 2002fff8, to register 0
Failed to assign value 80011d4, to register 0

If I use the command HAL_CAN_GetTxMailboxesFreeLevel it works normally or if I use RUN it works normally on the board, but I would like it to work in debug to see some information through the STM32CubeIDE

[SRedd.5]

My understanding is when in debug mode some of the features like CAN may not work as the timing of the CAN protocol may expire.

[matheuscaltran]

Thanks for the answer. From the test I did, if I run the debug run(Resume) and put HAL_CAN_GetTxMailboxesFreeLevel in the live expression it gives this error

If I remove it from live expression to run (Resume) it works normally

Why does this happen is it a bug?

[SRedd.5 · Accepted solution]

My understanding is you can have a global variable in expression not a function. 

[matheuscaltran]

It seems like that's right, create a global variable being the function and it didn't give that error when reading the expression