Reallocating the UART pins

Questions » Reallocating the UART pins

siva surendar

8 years, 3 months ago.

Hello

I have a situation where i need 4 UARTs wtih LPC824. However two of them are mutually exclusive. So I am was hoping there was a way to change pin allocations to use 1 or the other based on time . To Try i did the following program. However it fails with "No UART Available"

<code> RawSerial serialPorts[3] = {RawSerial(USBTX,USBRX),RawSerial(P0_4,P0_0), RawSerial(P0_19,P0_18)};

DigitalOut dummy1(P0_6,1);

DigitalOut dummy2(P0_7,1);

while(1) {

First set of allocation

dummy1 = DigitalOut(P0_6,1);

dummy2 = DigitalOut(P0_7,1);

serialPorts[2] = RawSerial(P0_19,P0_18);

serialPorts[2].putc('1');

wait(7);

Second set of allocation

dummy1 = DigitalOut(P0_19,1);

dummy1 = DigitalOut(P0_18,1);

serialPorts[2] = RawSerial(P0_6,P0_7);

serialPorts[2].putc('2');

wait(7); }

</code>

2 Answers

Andy A

8 years, 3 months ago.

Did you try deleting and creating the serial port object when you need to switch?

RawSerial *sharedPort = null;

void switchToPortOne() {
  if (sharedPort)
    delete sharedPort;

  sharedPort  = new RawSerial(P0_19,P0_18);
}

void switchToPortTwo() {
  if (sharedPort)
    delete sharedPort;

  sharedPort  = new RawSerial(P0_6,P0_7);
  sharedPort->baud(9600); // etc for any non-default setup required.
}

main() {
  switchToPortOne();
  sharedPort->putc('1');
  switchToPortTwo();
  sharedPort->putc('2');
}

I have no idea if this will work, it will be slow when switching but id does avoid two serial objects trying to use the same uart at the same time.

Oh and << >> rather than < > around to code tags to make them work ;-)

Accepted Answer

Andy Awesome. Looks like it worked

Pardon the basic question. I have an array. How will the syntax be? ex:

RawSerial serialPorts[3] = {RawSerial(P0_25,P0_26),RawSerial(USBTX,USBRX), RawSerial(P0_21,P0_22)}

Thanks for <<code>> pointer. Have always wondered why it didnt work

When I tried to SWM pin allocation ,Strangely, the first sharedPort worked only once (in a loop) and then it would throw out garbage, The second shared port worked well.. Heres my code


    LPC_SYSCON->SYSAHBCLKCTRL |= (1<<7);

    LPC_SWM->PINASSIGN0 = 0xffffffffUL; 

    LPC_SWM->PINASSIGN0 = 0xffff1213UL;

    LPC_SYSCON->SYSAHBCLKCTRL |= (0<<7);

posted by siva surendar 21 Sep 2016

Sanjiv Bhatia

8 years, 3 months ago.

Varying with your UART needs (speed; handshake lines, etc.), perhaps you could bit-bang out the UART model(s) that are required ? There are also SPI based UARTs from assorted silicon vendors but often these SPI UARTs cost more than the CPU with the requested resources of multiple UARTs.

Reference reading: https://developer.mbed.org/forum/mbed/topic/2092/

siva surendar

Important changes to forums and questions

8 years, 3 months ago.