my linux C program cannot receive data from Arduino through USB Serial - linux

Question

My Linux C application cannot receive bytes from Arduino
Hi all, I intend to use Arduino Mega 2560 as a programmer for AT89S52 (a family of 8051 microprocessor). The Arduino board connects to PC via USB Serial cable.
At first I need to write a program in my Ubuntu to communicate with Arduino board. My program can open connection and write bytes to Arduino properly (I tested by turning led on/off), but the problem is that the Linux program cannot receive data from Arduino.
I already searched through many tutorials and forums but still cannot resolve the problem, so I post question here and hope that someone can help me.
Below is my functon used to open connection to device
AT89S_EID usbserial_open ( char* dev_name,
UsbSerialDevice* dev_ptr,
int baudrate,
int config ) {
speed_t io_baudrate = B9600;
if (dev_name == NULL || dev_ptr == NULL)
{
return AT89S_EID_ARG_NULL;
}
if (baudrate != US_BAUDRATE_9600
&& baudrate != US_BAUDRATE_19200
&& baudrate != US_BAUDRATE_115200)
{
return AT89S_EID_SERIAL_BAUDRATE_INVALID;
}
if (config != US_CONFIG_8N1
&& config != US_CONFIG_7E1
&& config != US_CONFIG_7O1)
{
return AT89S_EID_SERIAL_CONFIG_INVALID;
}
// store device name
strcpy(dev_ptr->name, dev_name);
// open device
dev_ptr->fd = open (dev_ptr->name,
O_RDWR | O_NOCTTY | O_NDELAY | O_NONBLOCK);
if (dev_ptr->fd < 0)
{
return AT89S_EID_SERIAL_OPEN;
}
// get current termios settings
if (tcgetattr(dev_ptr->fd, &dev_ptr->tios) < 0)
{
return AT89S_EID_SERIAL_GET_ATTR;
}
// set input/output baudrdate
if (baudrate == US_BAUDRATE_9600)
io_baudrate = B9600;
else if (baudrate == US_BAUDRATE_19200)
io_baudrate = B19200;
else if (baudrate == US_BAUDRATE_115200)
io_baudrate = B115200;
if (cfsetispeed(&dev_ptr->tios, io_baudrate) != 0
|| cfsetospeed(&dev_ptr->tios, io_baudrate) != 0)
{
return AT89S_EID_SERIAL_SET_IOSPEED;
}
// enable receiver, ignore status line
dev_ptr->tios.c_cflag |= (CREAD | CLOCAL);
// set config
if (config == US_CONFIG_8N1)
{
dev_ptr->tios.c_cflag &= ~PARENB;
dev_ptr->tios.c_cflag &= ~CSTOPB;
dev_ptr->tios.c_cflag &= ~CSIZE;
dev_ptr->tios.c_cflag |= CS8;
}
else if (config == US_CONFIG_7E1)
{
dev_ptr->tios.c_cflag |= PARENB;
dev_ptr->tios.c_cflag &= ~PARODD;
dev_ptr->tios.c_cflag &= ~CSTOPB;
dev_ptr->tios.c_cflag &= ~CSIZE;
dev_ptr->tios.c_cflag |= CS7;
}
else if (config == US_CONFIG_7O1)
{
dev_ptr->tios.c_cflag |= PARENB;
dev_ptr->tios.c_cflag |= PARODD;
dev_ptr->tios.c_cflag &= ~CSTOPB;
dev_ptr->tios.c_cflag &= ~CSIZE;
dev_ptr->tios.c_cflag |= CS7;
}
// no HW flow control
dev_ptr->tios.c_cflag &= ~CRTSCTS;
// no input processing (raw input)
dev_ptr->tios.c_iflag &= ~(IXON | IXOFF | IXANY);
// other input settings
dev_ptr->tios.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);
// no output processing (raw output)
dev_ptr->tios.c_oflag &= ~OPOST;
// control character settings
dev_ptr->tios.c_cc[VMIN] = 1; // wait for 1 minimum chacacter received
dev_ptr->tios.c_cc[VTIME] = 0; // no timeout when waiting for charater
// commit new settings
if (tcsetattr(dev_ptr->fd, TCSANOW, &dev_ptr->tios) < 0)
{
return AT89S_EID_SERIAL_SET_ATTR;
}
// wait for device reset & sync up
usleep(1500 * 1000);
return AT89S_EID_OK;
} /* usbserial_open */
And this is the receiving function:
AT89S_EID usbserial_recv ( UsbSerialDevice* dev_ptr,
unsigned char* data_ptr,
int data_len ) {
int read_byte = 0;
char b[1];
if (dev_ptr == NULL
|| data_ptr == NULL)
{
return AT89S_EID_ARG_NULL;
}
// block reading
fcntl(dev_ptr->fd, F_SETFL, 0);
// start receiving data
while (read_byte < data_len)
{
if (read(dev_ptr->fd, b, 1) > 0)
{
data_ptr[read_byte++] = *b;
}
else
{
if (errno == EAGAIN)
continue;
else if (errno == ETIMEDOUT)
break;
else
return AT89S_EID_SERIAL_RECV;
}
}
return AT89S_EID_OK;
} /* usbserial_recv */
So sorry for posting a long code :)
I already searched through many tutorials and forums but still cannot resolve the problem. I believe that the Arduino code is working fine because I used some other tools to test it (e.g.: minicom)

Answer 1

I resolved my problem. Just add flush function when open the connection to device, everything can be working fine.
tcflush(fd, TCIOFLUSH);