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RS485 on 52259 MQX 3.8

Question asked by Toe on Feb 16, 2012
Latest reply on Feb 17, 2012 by David E Seymour

So I was trying to get a 485 implementation working properly in mqx.  I have an enable pin that needs to be turned off after I am done sending a message.  I realized that this was being turned off before all of the data had been sent.


I'm using the interrupt version of the serial driver in MQX and I am calling fflush after writing to the device with the assumption that it would return when all the data had been sent.


I noticed that there is a command that is available in the Kinetis parts that for some reason is left out of the coldfire parts:



The rs485.c example tries to use it and throws an error and the comment says "use newer MQX version".  Funny...


So I added the code in serl_pol_mcf52xx.c in the function _mcf52xx_uart_serial_polled_ioctl and wanted to post it here if it might help someone else.  It probably should be added to the MQX codebase.

case IO_IOCTL_SERIAL_WAIT_FOR_TC:    while(!(uart_ptr->READ.USR & MCF52XX_UART_USR_TXEMP)) ;    break;


Now if I call that before disabling my enable pin I don't miss any data on my line.