5 years, 7 months ago.

FRDM-K64F board - using two UARTs, both with IRQs

I'm trying to use two UARTs on the NXP FRDM-K64F board, UART4 and UART2. I am able to get some of it working, but other parts are not working:

• UART4 TX without interrupt - working
• UART4 TX interrupt - interrupt triggers over and over again https://os.mbed.com/questions/81130/Serial-Tx-interrupt-going-to-fire-excess/
• UART4 RX with or without interrupt - working
• UART2 TX without interrupt - working
• UART2 RX with interrupt - not working (THIS is what my question is about)

Is there some reason why both UART2 and UART4 on the K64F cannot be used simultaneously, both with RX interrupt routines?

I tried wiring the two RX pins together, with UART2 and UART4 RX IRQs enabled. Only the UART4 interrupt occurs. I tried disabling the UART4 RX interrupt and enabling the UART2 RX interrupt. UART2 RX interrupt does not occur.

K64F chip, 100-LQFP package, pin mapping:

• board pin J2-8, signal name PTD2, MCU pin 95, UART2_RX, pin map function 3
• board pin J2-10, signal name PTD3, MCU pin 96, UART2_TX, pin map function 3
• board pin J199-3, signal name PTC14, MCU pin 86, UART4_RX, pin map function 3
• board pin J199-4, signal name PTC15, MCU pin 87, UART4_TX, pin map function 3

Note, UART4 is not pin mapped in default mbed-dev library. I edited mine to add pin mapping for UART4, and left all the other pin maps untouched.

Regards, Carl