problem with serial port
I am currently working with the beagle board in which Linux is
ported. I have written program in it so that It continuously reads the
data coming to the serial port.I send the requests(at every 1 second)
to it by modbus tester(In another PC) but when it reads the requests,
immediately it(beagleboard) sends the garbage bytes to the serial
port.I don't write to the serial port or nothing at all do to write
anything to the serial port(in beagle board) still it writes
immediately after reading the requests.
I have attached a piece of code at beagle board side..(assuming
all necessary declaration)
int main()
{
int num_read,i,j,l;
char read_buffer[11];
char *nums_read = &read_buffer;
char nums[] = {0x02,0x04,0x00,0x00,0x00,0x02,0x71,0xf8};
char *nums_write = &nums;
serial_port_open();
while(1)
{
signal (SIGINT, (void*)sigint_handler);
tcflush(serial_port,TCIOFLUSH);
// The main program loop:
for(l=0;l<10;l++)
{ for(i=0;i<65535;i++)
{
if (serial_port != -1)
{
num_read = serial_port_read(nums_read, 9);
if (num_read > 0)
{
goto pa;
}
}
}
}
pa:j=1;
}
}
int serial_port_open(void)
{
struct termios options;
serial_port = open(PORT_NAME, O_RDWR | O_NONBLOCK);
if (serial_port != -1)
{
printf("Serial Port open\n");
tcgetattr(serial_port,&options_original);
tcgetattr(serial_port, &options);
cfsetispeed(&options, B9600);
cfsetospeed(&options, B9600);
options.c_cflag |= (CLOCAL | CREAD);
options.c_lflag |= ICANON;
tcsetattr(serial_port, TCSANOW, &options);
}
else
printf("Unable to open /dev/ttyS2\n");
return (serial_port);
}
int serial_port_read(char *nums_read, size_t max_chars_to_read)
{
int i,l;
int chars_read = read(serial_port, nums_read, max_chars_to_read);
usleep(20000);
tcflush(serial_port,TCIOFLUSH);
return chars_read;
}
A part of the observation of free serial monitor is written
here.Request is issued by the modbus tester and answer(undesired) is
given by beagleboard.I don't know how it writes into the serial
port...please help me work out this problem as soon as possible...
Request:
01 01 00 00 00 64 3D E1 01 01 00 00 00 64 3D E1 01 01 00 00 00 64
3D E1
Answer:
5E 41
Request:
01 01 00 00 00 64 3D E1 01 01 00 00 00 64 3D E1 01 01 00 00 00 64
3D E1 01 01 00 00 00 64 3D E1
Answer:
5E 41
Request:
01 01 00 00 00 64 3D E1
Answer:
5E 41
..........