UART

簡介：UART
在linux下，目錄通常是 /dev/ttyxxx，
最快的測法，就是開兩個minicom來test (ex: uart0 傳給 uart1)
Code Bookmark

• Embedded Linux UART的使用 ( 有詳細的termios介紹 )
• Cubieboard Docs  (這個比較好用)

不要開ssh 去cat /dev/ttyXX測，會掉字元

「轉貼 Cubieboard Docs」

/********************************************************************
 **************************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)); 
    tcdrain(fd);    /* delay for output */
    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++;
    }
}


「轉貼 Cubieboard Docs」


BTW: Android C++版 (沒試過，共4頁)