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====== How To Use The Uart ======

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//__About this Article__//
  * **Author**: allen --- allen@cubietech.com --- 2014/03/26 16:50
  * **Copyrights**: [[http://creativecommons.org/licenses/by-sa/3.0/|CC Attribution-Share Alike 3.0 Unported]]
  * **Contributors**: [[http://cubieboard.org/|Cubieboard Community]] : ...
</WRAP></WRAP>

===== 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 ====
Cubietruck         [[http://docs.cubieboard.org/a20-cubietruck_gpio_pin]]

Cubieboard 1 2 [[http://docs.cubieboard.org/cubieboard1_and_cubieboard2_gpio_pin]]

Fex Guide   [[http://linux-sunxi.org/Fex_Guide]]
===== Open the port =====
<code>
#mount /dev/nanda /mnt
#cd /mnt
#bin2fex  script.bin script.fex
#vi script.fex   

</code>
Modify the script.fex to open the uart3 ，uart4 as below ：   
 
<code>
[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>  
</code>


Save the modification.
<code>
#fex2bin script.fex  script.bin
#reboot
</code>

After the reboot ,the uart3 and uart4 are available.

<note tip> **remember save as script.bin and reboot**</note>


===== Test the uart  =====


Write a internal loopback program  to test the uart .
<code>
#vi uart_test.c 
</code>


Edit the program 
<code>
/********************************************************************
 **************************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++;
	}
}
</code>

Install software build the compiled enviroment .
<code>

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

</code> 

To test uart3 should make sure the PG06 and PG07 internal loopback,use Dupont Line connect them .

If you only open the uart0 3 4,  uart3 is mapping the device ttyS1.

While open the uart0 2 3 4,  uart3 is mapping the device ttyS2.

<code>
#./uart_test ttyS1 // or ttyS2
</code>

The termial will prinf as below,it prove the uart3 is working .
{{:tutorials:common:选区_052.png?600|}}

=== See Also ===

<WRAP noprint>
{{tag>Cubieboard Cubietruck}}
</WRAP>
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