topic Re: RS485 half-duplex SET GPIO to hardware flow control in MQX Software Solutions

RS485 half-duplex SET GPIO to hardware flow control

edgardocerone — Fri, 08 Feb 2013 20:51:18 GMT

Hi all,
I'm currently using, MQX 4.0, PXS2010 and RS-485 transceiver (SP485EE). (my board, not the tower)

I'm using the example rs485.c with hardware flow control:

rs485_dev = fopen (RS485_CHANNEL, (const char *) IO_SERIAL_HW_485_FLOW_CONTROL);

twr-pxs2010 connects GPIO[51] -> DE, GPIO [12] -> RE.

my board connects GPIO[98] -> DE, GPIO [99] -> RE.

My question is how to change these pins in the MQX, to work with DE / RE automatically?

Thanks in advance,
Eddie

Re: RS485 half-duplex SET GPIO to hardware flow control

Martin_ — Mon, 11 Feb 2013 06:31:36 GMT

Hello,

PXS20 LinFlex module doesn't implement hardware signal for RS-485 transceiver DE (Driver Output Enable). It has only TXD and RXD signals.

IO_SERIAL_HW_485_FLOW_CONTROL open flag is not supported on MQX 4.0 PXS20 BSP, and thus the DE signal would need to be implemented using a GPIO output and user software. MQX I/O User's Guide describes the steps for this in chapter 5.11.

Re: RS485 half-duplex SET GPIO to hardware flow control

edgardocerone — Mon, 11 Feb 2013 15:21:51 GMT

Hi Martin,

Thank you for answering me!, I will implement DE signal by software.

Re: RS485 half-duplex SET GPIO to hardware flow control

barbercolman — Mon, 11 Feb 2013 19:03:58 GMT

Hello

Where do I do I find if a processor supports the IO_SERIAL_HW_485_FLOW_CONTROL? I will be using a I20 processor. MK20DN512VLK10.

Re: RS485 half-duplex SET GPIO to hardware flow control

Martin_ — Tue, 12 Feb 2013 06:45:18 GMT

UART module on Kinetis parts has support for RS-485 in hardware (there is dedicated transmitter RTS output signal for this).

If there is hardware support in the module, IO_SERIAL_HW_485_FLOW_CONTROL open flag is supported in MQX serial driver.

On Kinetis, if we open serial device with IO_SERIAL_HW_485_FLOW_CONTROL flag, the driver will enable RTS signal in the port control module, and it will also configure UART module MODEM register for this functionality.

Re: RS485 half-duplex SET GPIO to hardware flow control

barbercolman — Tue, 12 Feb 2013 12:51:15 GMT

Thanks for help. Freescale does some very good things. Just connecting all the dots takes some work.