I am reading binary data from a serial port on Phidget sbc using Linux to get a command from an application running on a PC. I wrote a test program in VB to read the data into a byte array and convert it to decimal to use it but can’t figure out how to do it in c. I am unable to come up with anything with the research I have done on the internet.

Command sent from PC is 0x0F.

To check if I am getting correct data I read the data and send it back. Here is what I get back. Returned data has a carriage return added to it.

Hex Display 0F00 0000 0D

‘\’ Display \0F\00\00\00\r

Normal display just display a strange character.

This tells me that the data is there that I can use, but can’t figure out to extract the value 0F or 15.

How can I convert the incoming data to use it?

I tried converting the received data using strtol, but it returns 0. I also tried setting the port to raw but it did not make any difference.

unsigned char buffer1[1];
int ReadPort1()
{
int result;

result = read(file1, &buffer1,1);

if(result > 0)
{
    WritePort1(buffer1);
    sprintf(tempstr, "Port1 data %s %d", buffer1, result);
    DisplayText(2,tempstr);
}
return result;
}

Port Open/Setup

void OpenPort1()
{
//file1 = open("/dev/ttyUSB1", O_RDWR | O_NOCTTY | O_NONBLOCK);
     file1 = open("/dev/ttyUSB1", O_RDWR | O_NOCTTY | O_NODELAY);

if(file1 < 0)
    printf("Error opening serial port1.\n");
else
{
    SetPort(file1, 115200, 8, 1, 0, 1);
    port1open = 1;
}
}


void SetPort(int fd, int Baud_Rate, int Data_Bits, int Stop_Bits, int Parity, int raw)
{
    long BAUD;                      // derived baud rate from command line
    long DATABITS;
    long STOPBITS;
    long PARITYON;
    long PARITY;

struct termios newtio;

  switch (Baud_Rate)
  {
    case 115200:
        BAUD = B115200;
        break;
     case 38400:
        BAUD = B38400;
        break;
     case 19200:
        BAUD  = B19200;
        break;
     case 9600:
        BAUD  = B9600;
        break;
  }  //end of switch baud_rate
  switch (Data_Bits)
  {
     case 8:
     default:
        DATABITS = CS8;
        break;
     case 7:
        DATABITS = CS7;
        break;
     case 6:
        DATABITS = CS6;
        break;
     case 5:
        DATABITS = CS5;
        break;
  }  //end of switch data_bits
  switch (Stop_Bits)
  {
     case 1:
     default:
        STOPBITS = 0;
        break;
     case 2:
        STOPBITS = CSTOPB;
        break;
  }  //end of switch stop bits
  switch (Parity)
  {
     case 0:
     default:                       //none
        PARITYON = 0;
        PARITY = 0;
        break;
     case 1:                        //odd
        PARITYON = PARENB;
        PARITY = PARODD;
        break;
     case 2:                        //even
        PARITYON = PARENB;
        PARITY = 0;
        break;
  }  //end of switch parity

  newtio.c_cflag = BAUD | DATABITS | STOPBITS | PARITYON | PARITY | CLOCAL | CREAD;   
  newtio.c_iflag = IGNPAR;

  if(raw == 1)
  {
        newtio.c_oflag &= ~OPOST;
        newtio.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); 
  }
  else
  {
        newtio.c_lflag = 0;       //ICANON;
        newtio.c_oflag = 0;
  }

  newtio.c_cc[VMIN]=1;
  newtio.c_cc[VTIME]=0;
  tcflush(fd, TCIFLUSH);
  tcsetattr(fd,TCSANOW,&newtio);
}