I didn't get any answers to my previous question ( Usb-serial writing and reading data issue in Debian Gnu/Linux ) so I'm trying a different approach now.
I plugged my gauge to Windows, ran a proprietary program and checked COM port settings settings are here.
Then I wrote some code based on this article. Here what I have got
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdio.h>
#include <termios.h>
#define DEVICE "/dev/ttyUSB0"
#define WRITE_SPEED B1200
#define READ_SPEED B1200
#define PARITY ~PARENB
#define STOPBITS ~CSTOPB
#define DATASIZE CS8
#define HARDWARE_FLOW_CONTROL ~CRTSCTS
#define RECEIVER CREAD
#define MODEM_CONTROL_LINES CLOCAL
#define START_STOP_INPUT_CONTROL IXON
#define START_STOP_OUTPUT_CONTROL IXOFF
#define ANY_CHARACTER_RESTORE_STOPPED_OUTPUT ~IXANY
#define CANONICAL_MODE ~ICANON
#define PRINT_ECHO ECHO
#define ECHO_NEW_LINE ECHONL
#define ERASE_CHARACTER ECHOE
#define APPLICATION_DEFINED_CHARACTER IEXTEN
#define GENERATE_SIGNALS ISIG
#define OUTPUT_PROCESSING OPOST
#define SEND_TIMES_COUNT 1
#define SLEEP_TIME 0
unsigned int HEX_DATA_INPUT[] = {0xFF, 0x3A, 0x32, 0x34, 0x31, 0x3B, 0x30, 0x3B, 0x36, 0x35, 0x34, 0x30, 0x35, 0x0D};
unsigned int HEX_DATA_OUTPUT[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
int HEX_DATA_SIZE = 14;
/*setup terminal
fd - terminal file descriptor
returns 0 if everything fine and
not 0 otherwise
*/
int setupTerminal(int fd) {
int ret = 0;
struct termios SerialPortSettings;
tcgetattr(fd, &SerialPortSettings);
cfsetispeed(&SerialPortSettings, WRITE_SPEED);
cfsetospeed(&SerialPortSettings, READ_SPEED);
SerialPortSettings.c_cflag &= STOPBITS;
SerialPortSettings.c_cflag &= ~CSIZE;
SerialPortSettings.c_cflag |= DATASIZE;
SerialPortSettings.c_cflag &= HARDWARE_FLOW_CONTROL;
SerialPortSettings.c_cflag |= RECEIVER | MODEM_CONTROL_LINES;
SerialPortSettings.c_iflag &= (START_STOP_INPUT_CONTROL | START_STOP_OUTPUT_CONTROL | ANY_CHARACTER_RESTORE_STOPPED_OUTPUT);
SerialPortSettings.c_iflag &= (CANONICAL_MODE | PRINT_ECHO | ECHO_NEW_LINE | ERASE_CHARACTER| APPLICATION_DEFINED_CHARACTER | GENERATE_SIGNALS);
SerialPortSettings.c_oflag &= OUTPUT_PROCESSING;
if((tcsetattr(fd, TCSANOW, &SerialPortSettings)) != 0) {
/*Error while changing port settings*/
printf("Error in setting attributes. Error text:%s\n", strerror(errno));
ret = errno;
}
}
int main(int argc, char **argv)
{
int ret = 0;
/*We are opening serila-usb port here*/
int fd = open(DEVICE, O_RDWR | O_NOCTTY | O_NONBLOCK | O_NDELAY);
if(fd != -1) {
/*port has been opened successfully*/
if(setupTerminal(fd) == 0) {
/*Terminal has been st up correctly*/
/*discard old data in the buffer*/
tcflush(fd, TCIFLUSH);
/*writing data to the port*/
int writeRet = -1;
int i = 0;
for(i = 0; i < SEND_TIMES_COUNT; ++i) {
writeRet = write(fd, HEX_DATA_INPUT, HEX_DATA_SIZE * sizeof(unsigned int));
printf("writeRet=%d\n", writeRet);
}
if(writeRet != -1) {
/*writing to the port succeffull*/
/*Delay before reading data*/
sleep(SLEEP_TIME);
int readRet = read(fd, HEX_DATA_OUTPUT, HEX_DATA_SIZE * sizeof(unsigned int));
if(readRet != -1) {
/*reading from the port successfully*/
printf("readRet=%d\n", readRet);
}
else {
/*Error while reading from the port*/
printf("error while reading from the port. Error code:%d; Error message:%s\n", errno, strerror(errno));
ret = errno;
}
}
else {
/*Error while writing data to the port*/
printf("writing to the port failed. Error text: %\n", strerror(errno));
ret = errno;
}
}
else {
printf("error opening %s. Error message:%s\n", DEVICE, strerror(errno));
ret = errno;
}
}
else {
printf("error opening port. Error number: %d; error text: %s\n", errno, strerror(errno));
ret = errno;
}
int cdf = close(fd);
printf("cdf=%d\n", cdf);
printf("press any key to exit\n");
getchar();
return ret;
}
This code allows me to successfully write 56 bytes to the port, but reading attempt gives me error 11 "Resource temproary unavailable". I guess this is because of wrong settings I made to termios structure but I don't know which. In Windows I used software "Serial port monitor" to trace data exchange between device and proprietary program, trace file is located here under the nameexchange.xlsx I tried to set up port in my program the same way the proprietary program did according to the info in this file but with no luck. Could you please help me find out where is my mistake is?
