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tutorials:common:how_to_use_the_uart

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How To Use The Uart

About this Article

Abstract

Here is the guide to teach that how to enable the uart port on cubiboard and how to test the uart port is available .

Cubieboard pin

Open the port

#mount /dev/nanda /mnt
#cd /mnt
#bin2fex  script.bin script.fex
#vi script.fex

Modify the script.fex to open the uart3 ,uart4 as below :

[uart_para3]
uart_used = 1
uart_port = 3
uart_type = 4
uart_tx = port:PG06<4><1><default><default>
uart_rx = port:PG07<4><1><default><default>
uart_rts = port:PG08<4><1><default><default>
uart_cts = port:PG09<4><1><default><default>

[uart_para4]
uart_used = 1
uart_port = 4
uart_type = 2
uart_tx = port:PG10<4><1><default><default>
uart_rx = port:PG11<4><1><default><default>

Save the modification.

#fex2bin script.fex  script.bin
#reboot

After the reboot ,the uart3 and uart4 are available.

remember save as script.bin and reboot

Test the uart

Write a internal loopback program to test the uart .

#vi uart_test.c

Edit the program

/********************************************************************
 **************************uart_test*********************************
 ********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <sys/time.h>
#include <string.h>

#define TRUE 1
#define FALSE -1

int speed_arr[] = {B115200, B38400, B19200, B9600, B4800, B2400, B1200, B300,
        B38400, B19200, B9600, B4800, B2400, B1200, B300, };

int name_arr[] = {115200, 38400,  19200,  9600,  4800,  2400,  1200,  300,
        38400,  19200,  9600, 4800, 2400, 1200,  300, };

void set_speed(int fd, int speed)
{
  int i;
  int status;

  struct termios Opt;
  tcgetattr(fd,&Opt);

  for (i= 0;i<sizeof(speed_arr)/sizeof(int);i++)
  {
        if(speed == name_arr[i])
       {
           tcflush(fd, TCIOFLUSH);


        cfsetispeed(&Opt, speed_arr[i]);

        cfsetospeed(&Opt, speed_arr[i]);


        status = tcsetattr(fd, TCSANOW, &Opt);

        if(status != 0)
           perror("tcsetattr fd1");

             return;
         }
        tcflush(fd,TCIOFLUSH);
   }
}

int set_Parity(int fd,int databits,int stopbits,int parity)
{
    struct termios options;
   if( tcgetattr( fd,&options)!= 0)
   {
          perror("SetupSerial 1");

           return(FALSE);
    }

   options.c_cflag &= ~CSIZE;


  switch(databits)
   {
          case 7:
          options.c_cflag |= CS7;
          break;

       case 8:
        options.c_cflag |= CS8;
        break;

       default:
        fprintf(stderr,"Unsupported data size\n");

        return (FALSE);
    }

   switch(parity)
      {
          case 'n':
        case 'N':
        options.c_cflag &= ~PARENB;    /* Clear parity enable */
        options.c_iflag &= ~INPCK;    /* Enable parity checking */
        options.c_iflag &= ~(ICRNL|IGNCR);
        options.c_lflag &= ~(ICANON );
        break;


    case 'o':

    case 'O':
        options.c_cflag |= (PARODD | PARENB);
        options.c_iflag |= INPCK;    /* Disnable parity checking */
        break;


    case 'e':

    case 'E':
        options.c_cflag |= PARENB;    /* Enable parity */
        options.c_cflag &= ~PARODD;
        options.c_iflag |= INPCK;    /* Disnable parity checking */
        break;


    case 'S':

    case 's':  /*as no parity*/
        options.c_cflag &= ~PARENB;
        options.c_cflag &= ~CSTOPB;
        break;

         default:
        fprintf(stderr,"Unsupported parity\n");

        return (FALSE);
    }

   switch(stopbits)
      {

      case 1:

      options.c_cflag &= ~CSTOPB;

    break;


    case 2:

    options.c_cflag |= CSTOPB;

    break;


    default:

    fprintf(stderr,"Unsupported stop bits\n");


    return (FALSE);
    }

  /* Set input parity option */

   if(parity != 'n')
          options.c_iflag |= INPCK;
          options.c_cc[VTIME] = 150; // 15 seconds
       options.c_cc[VMIN] = 0;

         tcflush(fd,TCIFLUSH); /* Update the options and do it NOW */

  if(tcsetattr(fd,TCSANOW,&options) != 0)
  {
          perror("SetupSerial 3");

        return (FALSE);
    }

   return (TRUE);
}

int main(int argc, char **argv)
{
    int fd;
    int nread;
    int nwrite;
    int n=0;
    int i=0;
    char buffer[15];
    char devname_head[10] = "/dev/";
    char dev_name[20];

     if(argc < 2)
    {
      printf("Please input './test_uart ttySx'\n");
      exit(1);
    }
    else
    {
        strcpy(dev_name, devname_head);
        strcat(dev_name, argv[1]);
    }

    fd = open(dev_name, O_RDWR);
    if(fd < 0)
    {
        perror("error to open /dev/ttySx\n");
        exit(1);
    }


    if (fd > 0)
    {
        set_speed(fd,115200);
    }
    else
    {
        printf("Can't Open Serial Port!\n");

        exit(0);
    }

      if (set_Parity(fd,8,1,'N') == FALSE)
      {
        printf("Set Parity Error\n");

        exit(1);
      }

    printf("\nWelcome to uart_test\n\n");

   memset(buffer,0,sizeof(buffer));

   char test[15] = "hello world";

   nwrite = write(fd,test,strlen(test));
    if(nwrite < 0)
    {
        printf("write error\n");
    }

   printf("Send test data------>%s\n",test);

      while(1)
      {
        nread = read(fd,&buffer[n],1);
        if(nread < 0)
        {
            printf("read error\n");
        }

        printf("read char is -> %c \n",buffer[n]);

           if (strlen(buffer) == strlen(test))
           {
               printf("Read Test Data finished,Read Test Data is------->%s\n",buffer);

            memset(buffer,0,sizeof(buffer));
            printf("Send test data again------>%s\n",test);

            write(fd,test,strlen(test));
            n=0;
            sleep(1);

            continue;
        }
       n++;
    }
}

Install software build the compiled enviroment .

#apt-get install gcc build-essential
#gcc uart_test.c -o uart_test

To test uart3(or uart4) should make sure the PG06 and PG07 (or PG10 and PG11)internal loopback,use Dupont Line connect them .

If you only open the uart0 4, uart4 is mapping the device ttyS1.

While open the uart0 3 4, uart3 is mapping the device ttyS1. uart4 is mapping the device ttyS2.

#./uart_test ttyS1 // or ttyS2

The termial will prinf as below,it prove the uart3 is working .

See Also

tutorials/common/how_to_use_the_uart.1402313998.txt.gz · Last modified: 2014/06/09 19:39 by allen