UART data drop at low priority

[kmk_321994]

I am using an STM32F4 series MCU and have enabled two interrupts:

EXTI for edge trigger with Priority 6

Serial Driver UART with Priority 12

This means the EXTI interrupt has a higher priority than the UART interrupt. The EXTI interrupt is never missed.

Every time the EXTI interrupt occurs, the following callback is executed:

Code: Select all

chSysLockFromISR();
chVTSetI(..);
chSysUnlockFromISR();

The UART is configured at a baud rate of 230400 and receives approximately 3 kB every 200 ms. Data from the UART data register is read into a message queue with a buffer size of 32. From a thread, the data is then read from the queue into a FIFO buffer.

Byte drop doesn't happen every time. Is UART interrupt not going into pending state because of high priority ISR and hence the byte is dropped?

[Giovanni]

Hi,

That could only occur if the EXTI interrupt is triggered at a very high rate. Are you getting overflow events from the serial driver?

You can make an easy test: put UART priority above EXTI.

Giovanni