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#include <bits/types/time_t.h>
#include <errno.h> /* strerror() */
#include <fcntl.h> /* O_RDWR */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <time.h>
#include <unistd.h> /* write(), read(), close() */
int openSerialPort(char pathToPort[], int baudRate) {
static int serialPort;
struct termios serialTerminal;
serialPort = open(pathToPort, O_RDWR);
if (serialPort < 0) {
printf("Error open(): %s\n", strerror(errno));
return -1;
}
if (tcgetattr(serialPort, &serialTerminal) != 0) {
printf("Error tcgetattr(): %s\n", strerror(errno));
return -1;
}
serialTerminal.c_cflag |= CREAD;
/* serialTerminal.c_iflag &= ~(BRKINT | IGNBRK | INLCR | IGNCR | ICRNL | IXOFF
| IUTF8 | IUCLC | IXANY | IMAXBEL); */
serialTerminal.c_iflag &=
~(IGNBRK | BRKINT | INLCR | IGNCR | ICRNL | IXON | IXOFF | IUCLC | IXANY |
IMAXBEL | IGNPAR | PARMRK | INPCK | ISTRIP);
/* serialTerminal.c_lflag &= ~(ECHO | ECHONL | NOFLSH | ISIG | TOSTOP | ICANON
| IEXTEN | ECHOE | ECHOK); */
serialTerminal.c_lflag &= ~(ICANON | ISIG | ECHO | ECHONL | ECHOE | ECHOK);
/* serialTerminal.c_oflag &=
~(OLCUC | OCRNL | OPOST | OFILL | ONLCR | ONOCR | ONLRET | OFDEL); */
serialTerminal.c_oflag &= ~(OPOST);
serialTerminal.c_cc[VTIME] = 0;
serialTerminal.c_cc[VMIN] = 0;
cfsetispeed(&serialTerminal, baudRate);
cfsetospeed(&serialTerminal, baudRate);
if (tcsetattr(serialPort, TCSANOW, &serialTerminal) != 0) {
printf("Error tcsetattr(): %s\n", strerror(errno));
close(serialPort);
return -1;
}
return serialPort;
}
int readSerialPort(int serialPort) {
time_t start;
int bytesRead, bufferFree, idx, returnCode, isEnd;
int bufferSize = sizeof(char) * 256; /* initial size in bytes */
char *buffer = calloc(256, sizeof(char));
const char *responseCodes[8] = {"\r\nOK\r\n", "\r\nCONNECT\r\n",
"\r\nRING\r\n", "\r\nNO CARRIER\r\n",
"\r\nERROR\r\n", "\r\nNO DIALTONE\r\n",
"\r\nBUSY\r\n", "\r\nNO ANSWER\r\n"};
bytesRead = bufferFree = bufferSize;
returnCode = isEnd = 0;
start = time(NULL);
while (!isEnd) {
if (bufferFree < 1) {
bufferSize += sizeof(char) * 256;
buffer = realloc(buffer, bufferSize);
if (buffer == NULL) {
printf("Error realloc(): %s\n", strerror(errno));
returnCode = 1;
break;
}
}
bytesRead = read(serialPort, buffer + bufferSize - bufferFree, bufferFree);
if (bytesRead < 0) {
printf("Error read(): %s\n", strerror(errno));
returnCode = 1;
break;
} else if (bytesRead > 0) {
bufferFree -= bytesRead;
start = time(NULL);
} else if (bytesRead == 0 && difftime(time(NULL), start) > 180) {
printf("Response timeout\n");
returnCode = 1;
break;
} else {
for (idx = 0; (long unsigned)idx <
sizeof(responseCodes) / sizeof(responseCodes[1]);
idx++) {
if (strstr(buffer, responseCodes[idx]) != NULL) {
isEnd = 1;
break;
}
}
}
}
printf("%s", buffer);
free(buffer);
return returnCode;
}
int main() {
int serialPort;
serialPort = openSerialPort("/dev/serial0", 115200);
if (write(serialPort, "AT\r", sizeof("AT\r")) < 0) {
printf("Error write(): %s\n", strerror(errno));
close(serialPort);
return 1;
}
readSerialPort(serialPort);
if (write(serialPort, "ATI\r", sizeof("ATI\r")) < 0) {
printf("Error write(): %s\n", strerror(errno));
close(serialPort);
return 1;
}
readSerialPort(serialPort);
if (write(serialPort, "AT+COPS?\r", sizeof("AT+COPS?\r")) < 0) {
printf("Error write(): %s\n", strerror(errno));
close(serialPort);
return 1;
}
readSerialPort(serialPort);
close(serialPort);
return 0;
}
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