Hi, In this post about counting sempahores: https://sourceforge.net/p/freertos/discussion/382005/thread/5e30e7e0/ there was a link to implementing interrupts. I’m using a PIC32MX and I believe I have a conflict between my UART and USB interrupts. When I don’t use USB, my UART receive interrupt works fine. With USB data going back and forth, somehow I get an occasional byte in my UART ISR which is corrupted. I’m really confused about the max priority level in FreeRTS configuration and how I should configure the priorities of my ISRs. My UART interrupt is defined as follows, I believe in agreement with the FreeRTOS requirements: void attribute( (interrupt(IPL3SOFT), nomips16, vector(UART2VECTOR))) U2InterruptWrapper(void); But my USB ISR is defined by the Microchip USB implementation as follows: void attribute((interrupt(), vector(USB1_VECTOR))) _USB1Interrupt( void ); If I make USB priority 2, I get a general exception. If I make it 4, I still have the data corruption. BTW, the corruption is weird. At random times, my receive data buffer has a byte replaced by the byte received 3 bytes prior to the current byte. It’s as if the buffer index is modified, and always by a 3 byte offset. Any suggestions? Thanks, Dave

Are both interrupts using the FreeRTOS API, or just the UART interrupt? Regards.

The USB interrupt does not use the FreeRTOS wrapper. I might try adding that in now. Thanks, Dave