Wow I am speechless.
I guess for two reasons.
- Two thumbs up to @aggarg for his excellent debugging skill.
- Shame on NXP for providing this kind of driver to their customers.
The UART driver is from NXK SDK 2.6. This is really really crazy to write a driver to have its ISR behavior affected by application task priority.
When I reached out to them, they acted very innocent obviously saying that there is no known issue.
I guess this is NOT a bug as long as you keep your UART task(s) to be highest priority task.
I think this is insane. I never thought that NXP would write their driver in such manner.