UART Example

Target Side

/*
 * uartTask1.c
 *
 *  Created on: May 15, 2010
 *      Author: root
 */
#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#include <sys/prctl.h>
#include <sched.h>
#include <fcntl.h>
#include <termios.h>
 
#include "app.h"
 
#define DEVICE_FILE            ("/dev/ttyS2")
 
struct termios options;
 
void set_port(int fd)
{
    int status;
    // Get current settings for the port
    tcgetattr(fd, &options);
    // Set baud rate = 1200
    cfsetispeed(&options, B115200);
    cfsetospeed(&options, B115200);
    // Set 8 bits, no parity
    options.c_cflag &= ~PARENB;
    options.c_cflag &= ~CSTOPB;
    options.c_cflag &= ~CSIZE;
    options.c_cflag |= CS8;
    // Raw input
    options.c_lflag &= ~(IEXTEN |ICANON | ECHO | ECHOE | ISIG );
    // Check and strip parity bit.
    options.c_iflag = 0;
    // Disable software flow control
    options.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON | IXOFF | IXANY);
    // Output to be raw
    options.c_oflag &= ~(OPOST | OLCUC | ONLCR | OCRNL );
 
    options.c_cc[VTIME] = 0;
    options.c_cc[VMIN] = sizeof(uart_buffer_t);
 
    // Set new options for port
    status = tcsetattr(fd, TCSANOW, &options);
}
void uartTask1()
{
    int msgCount = 0,count = 0;
    int fd;
    struct timespec waitTime;
    uart_buffer_t buf_out,buf_in;
    struct sched_param param;
    param.sched_priority = 10;
//    sched_setscheduler(0,SCHED_FIFO,&param);
    waitTime.tv_nsec =  20 * MILI_SECOND;
    waitTime.tv_sec = 0;
    prctl(PR_SET_NAME,"UART1");
    printf("starting...%d\n",sizeof(uart_buffer_t));
 
    //sleep(20); // test purpose , wait to change the uart plug
 
    // create a test data
    memcpy(buf_in.buf ,"aaaaaaaaaabbbbbbbbbb"
                        "cccccccccc1111111111dddddddddd"
                        "eeeeeeeeee12345678901234567890"
                        "12345678901234567890",UART_BUFFER_SIZE );
 
    buf_in.len = UART_BUFFER_SIZE;
 
    // open serial device
    fd=open(DEVICE_FILE,O_RDWR | O_NOCTTY );
 
    // flush old input and output data if exists
    tcflush(fd,TCIOFLUSH);
 
    set_port(fd);
 
    puts("uartTask1 started");
    while(1)
    {
        int s;
        nanosleep(&waitTime,NULL);
        msgCount++;
        buf_in.msgNum = msgCount;
        buf_in.checksum = checksum(buf_in.buf,UART_BUFFER_SIZE);
 
        //send message
        s=write(fd,&buf_in,sizeof(uart_buffer_t));
 
        //wait for message to arrive
        read(fd,&buf_out,sizeof(uart_buffer_t));
 
        if(++count == 400)
        {
            //dump arrived message
            printf("Got Msg number=%d from UART\n=============\n",buf_out.msgNum);
            puts((char*)buf_out.buf);
            if(checksum(buf_out.buf,buf_out.len) == buf_out.checksum)
            {
                puts("message ok");
            }
            else
            {
                puts("error in checksum");
            }
            count = 0;
        }
    }
 
}

Host side

/*
 ============================================================================
 Name        : PcUARTApp.c
 Author      :
 Version     :
 Copyright   : Your copyright notice
 Description : Hello World in C, Ansi-style
 ============================================================================
 */
/*
 * uartTask1.c
 *
 *  Created on: May 15, 2010
 *      Author: root
 */
#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
#include <sys/prctl.h>
#include <fcntl.h>
#include <termios.h>
 
#pragma pack(1)
 
typedef struct {
    int msgNum;
    unsigned char buf[100];
    short int len;
    short int checksum;
}buffer_t;
 
#pragma pack()
 
struct termios options;
 
void set_port(int fd)
{
    int status;
    // Get current settings for the port
    tcgetattr(fd, &options);
    // Set baud rate = 1200
    // Set 8 bits, no parity
    options.c_cflag = B115200 | CRTSCTS | CS8 | CLOCAL | CREAD;
    // Check and strip parity bit.
    options.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
 
    options.c_oflag &= (~OPOST);
 
    options.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
    options.c_cc[VTIME] = 0;
    options.c_cc[VMIN] = sizeof(buffer_t);
 
    // Set new options for port
    status = tcsetattr(fd, TCSANOW, &options);
}
int main()
{
    int b;
    int fd;
    buffer_t buf1;
 
    printf("starting...%d\n",sizeof(buffer_t));
    fd=open("/dev/ttyS0",O_RDWR | O_NOCTTY );
    set_port(fd);
    tcflush(fd,TCIOFLUSH);
 
    puts("start ......");
    while(1)
    {
        b=read(fd,&buf1,sizeof(buffer_t));
        if(b > 0)
        {
            printf("Msg number=%d\n=============\n",buf1.msgNum);
            puts(buf1.buf);
            write(fd,&buf1,sizeof(buffer_t));
        }
 
    }
 
}