Read Beagle Board xM RS-232 Serial output

環境設置

• Beagle Board xM 使用 OTG USB 供電
• Beagle Board xM RS-232 Serial output 連接到電腦 USB to COM
• 軟體修改老師的 ext_uart.c 如下

#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 <string.h>
//#include <stdlib.h>
static char *serial_name[]={"/dev/ttyS0","/dev/ttyS1","/dev/ttySAC1","/dev/ttySAC2","/dev/ttyUSB0"};
int main(void)
{
 int  n, len,  fd_max,i;
  fd_set  readfds;
  char buffer[256];
 static struct termios oldtio,newtio;

 printf(" *** 0:ttyS0 ***\r\n,*** 1:ttyS1 ***\r\n,*** 2:ttySAC1 ***\r\n,*** 3:ttySAC2 ***\r\n,*** 4:ttyUSB0 ***\r\n");
 printf("*** please input the open serial : ");
 scanf("%d",&i);

 int fd = open(serial_name[i],O_RDWR | O_NOCTTY | O_NDELAY);//270
 if(fd<0){
  perror("Cannot Open Serial Port !\n");
 }
 else
  printf("open Serial Port success !\r\n");

 tcgetattr(fd,&oldtio);
 tcgetattr(fd,&newtio);


 cfsetispeed(&newtio,B115200);
 cfsetospeed(&newtio,B115200);

 //newtio.c_lflag&= ~(ICANON | ECHO | ECHOE | ISIG);
 newtio.c_lflag |= ICANON;

 newtio.c_cflag &= ~PARENB;


 newtio.c_cflag &= ~CSTOPB;


 newtio.c_cflag &= ~CSIZE;
 newtio.c_cflag |= CS8;


 newtio.c_oflag &= ~OPOST;


 newtio.c_cflag |= (CLOCAL | CREAD);

 newtio.c_iflag = 0;


 newtio.c_cc[VTIME] = 0;
 newtio.c_cc[VMIN] = 0;


 if(tcsetattr(fd,TCSAFLUSH,&newtio)<0)
 {
  printf("tcsetattr fail !\n");
  exit(1);
 }

    FD_ZERO(&readfds);
    FD_SET(fd, &readfds);
    fd_max = fd + 1;

    /* Do the select */
    //return 0;
    while(1)
    {

    n = select(fd_max,&readfds,NULL,NULL,NULL);
    memset(buffer, 0, sizeof(buffer));
    if (n<=0)
            printf("select failed");
     else
        {
            if (FD_ISSET(fd, &readfds))
                 {    char buf[16];
                  len=read(fd, buffer, 256);
                  fprintf(stderr, "%s", buffer);
                  /*
                 buffer[len] = '\0';
                       fprintf(stderr, "Readed %d data:%s\n",len, buffer);
                       sprintf(buf, "got data:%s\n",buf);
                         write(fd,buf,strlen(buf));
                         */
                 }
       }
    }
}

修改內容：

1. 增加 /dev/ttyUSB0 for USB to COM
2. Baud Rate 設為 115200
3. 採用 ICANON 模式
4. VTIME=0 && VMIN=0 : 立即讀取，若無資料則返回
5. 將讀到的資料直接顯示出來，並將寫回去的功能移除

程式讀到的結果如下：

U-Boot SPL 2011.12-00010-ga3eb89c (Jan 29 2012 - 14:53:43)

Texas Instruments Revision detection unimplemented

OMAP SD/MMC: 0

timed out in wait_for_bb: I2C_STAT=1000

reading u-boot.img

reading u-boot.img





U-Boot 2011.12-00010-ga3eb89c (Jan 29 2012 - 14:53:43)



OMAP36XX/37XX-GP ES1.2, CPU-OPP2, L3-165MHz, Max CPU Clock 1 Ghz

OMAP3 Beagle board + LPDDR/NAND

I2C:   ready

DRAM:  512 MiB

NAND:  0 MiB

MMC:   OMAP SD/MMC: 0

*** Warning - readenv() failed, using default environment



In:    serial

Out:   serial

Err:   serial

Beagle xM Rev C

No EEPROM on expansion board

No EEPROM on expansion board

Die ID #465600029ff800000168300f0d030023

Net:   Net Initialization Skipped

No ethernet found.

Hit any key to stop autoboot:  2     1     0 

The user button is currently NOT pressed.

SD/MMC found on device 0

reading uEnv.txt



** Unable to read "uEnv.txt" from mmc 0:1 **

Loading file "/boot/uImage" from mmc device 0:2 (xxa2)

在上面卡很久，只好等老師解釋了！！