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Unable to get UART4 working on FRDM-K64F

Question asked by dave408 on May 13, 2015
Latest reply on May 13, 2015 by dave408

I'm using a FRDM-K64F with a handful of peripherals.  At the moment, I cannot get UART4 to work.  I have PEx set up to use PTE24 and PTE25:


I'm using the same settings (with the exception of pins) for UART3 for an RS485 transceiver, and it works just fine.  But when I look at the output of TX on the scope, I get nothing.


Can anyone suggest something that I might be doing wrong?  Here's what I have done so far:


  • Double-checked the PEx auto-generated code and it looks correct.  Pin muxing is set properly for HW_UART4.  UART_DRV_Init() is called from Components_Init().
  • Stepped into the call to UART_DRV_SendDataBlocking for my RS485 and my UART4 code, and they follow the same path and supposedly send similar type of data, except that UART4 doesn't do anything on the pins.