I'm experiencing a weird problem with our QN9083 boards. They work fine until they get slightly warm. Not hot, just warm. A few degrees over room temperature. 26C-28C (measured internally). The boards operate when warm but when I cycle power, they won't boot until we cool them down. We've narrowed it down to something on the MCU. We can get a board in this state, touch the MCU with a cold cotton swab and it comes right up without any other intervention.
We've got 3 main suspects, none of which have left a smoking gun:
- We've scoped the input power and it's clean at the pin.
- I'm delving into the SystemInit() code to see if there's a default setting from the DK board that's somehow not compatible with ours. I'm still digesting the settings -- a lot of the PMU and VDD registers aren't documented very well.
- I've but an LED blink routine at the start of main() and it doesn't get hit when it boots warm so whatever the issue is, it's happening prior to my code getting called.
- I've gotten rid of the XTAL delay in SystemInit(). No change.
- We've got 12 boards all behaving the same. It could be a BGA issue?
- DK board doesn't exhibit this behavior.
Has anyone run into something similar?