K81 Uart 4 pin configuration: Uable to get signals to driver out of the chip on PTC14/PTC15 (PORTD20/PORTD21).

[jeffreystuber]

There must be more to configuring the PIN MUX than setting the port MUX alternate function.  UART4 appears to function as in put data in the FIFO and the transmit complete status set.  However the port PIN is not driven.    Any advice?

[Robin_Shen]

Hi Jeffrey,

Sorry for the late reply!
I have request the documents of K81, may receive them within 48 hours.

Have you check the value of PORTx_PCRn[MUX] during debug, whether it select correct alternate function that meet the Signal Multiplexing table?

And have you check the circuit of TWR-POS-K81F board, whether these pins are disconnect by DNP resistances.

Best Regards,

Robin

[jeffreystuber]

Hi Robin,

Thanks for the reply. The missing piece that I eventually found was configuring the pin as an output. All is well now.

Regards,

Jeff Stuber

[jeffreystuber]

Configuring TWR-POS-K81F board.