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K22FN512 and MQX UART (MUX and baudrate)

Question asked by Yvan BOURNE on Sep 23, 2015

I'm tryng to create a new project on a custom board (even on a FRDMK22F512) and MQX (I don't want to use KDS).

I had a lot of problem to porting librairies even with the cloning tool and problems to program / debug (because the Target Type is not present under CW : Re: MQ vs KDS ).


Now, after several lost days, I can run some little pieces of code


But on the UART side, I had found, I think, 2 bugs in MXQ :

1. MUX

2. Baud rate


1. MUX :

In the init_gpio.c files (from the TWRK22F120M) :


TWRK22F120M :

A14 - A15 : OK UART0

E0 - E1 (second error : MUX disable : 3 - 4...) : OK UART1

E16 - E17 : These pins are not present on none package : it's PTB2 and PTB3, not PORTE for UART2



I tried UART0 at 115200 in the user_config.h file. I had 172 KBd in Tx pin...

Even with the IOCTL function, same BR :

_mqx_uint baud ;



  baud = 19200 ;

  ioctl(uart0_handle, IO_IOCTL_SERIAL_SET_BAUD, &baud) ;


By writing manually the registers, I can have 115200Bds :

UART_MemMapPtr   uart = UART0_BASE_PTR;



  uart->BDH = 0 ;

  uart->BDL = 65 ; // 115200


I will continue just few days to find bugs, after, I'll give up (K22_100 is written as supported by MQX : Freescale MQX™ Software Solutions|Freescale).