We're using a PICO-IMX7 SOM (based on an iMX7D) and have discovered a problem. At 500ms after power-on, we experience a brief (around 2ms) spike on one of our outbound GPIO lines (see attached image). We assumed that the problem would be some rogue initialization code in the SPL but it actually seems to happen before any SPL code runs. We've tested this by using a dummy SPL that does nothing but loop forever (annotated hexdump attached) and the spike still occurs.
As it turns out, this spike can sometimes lead to a large, potentially damaging, current spike which means we have to get to the bottom of this.
The curious thing is that it doesn't happen until 500ms - surely by then the SPL should already be running? The pad that we see the spike on is SAI1_TXFS.
Does anyone have any idea about what could be causing this?
