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#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() */
#define BUFFER_SIZE 256
int openSerialPort(char pathToPort[]) {
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));
close(serialPort);
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, B115200);
cfsetospeed(&serialTerminal, B115200);
if (tcsetattr(serialPort, TCSANOW, &serialTerminal) != 0) {
printf("Error tcsetattr(): %s\n", strerror(errno));
close(serialPort);
return -1;
}
return serialPort;
}
int querySerialPort(int serialPort, char *input) {
time_t timeStart;
unsigned long idx;
int bytesRead, bufferFree, returnCode, isEnd,
bufferSize = sizeof(char) * BUFFER_SIZE; /* initial size in bytes */
char *txBuffer, *buffer = calloc(BUFFER_SIZE, 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"};
txBuffer = malloc(sizeof(char) * (strlen(input) + 2));
strncpy(txBuffer, input, sizeof(char) * (strlen(input) + 1));
strncat(txBuffer, "\r", 2 * sizeof(char));
if (write(serialPort, txBuffer, sizeof(char) * (strlen(txBuffer))) < 0) {
printf("Error write(): %s\n", strerror(errno));
free(txBuffer);
free(buffer);
return 1;
}
free(txBuffer);
bytesRead = bufferFree = bufferSize;
returnCode = isEnd = 0;
timeStart = time(NULL);
while (!isEnd) {
bytesRead =
read(serialPort, buffer + bufferSize - bufferFree, bufferFree - 1);
if (bytesRead < 0) {
printf("Error reading serial port\n");
returnCode = 1;
break;
}
else if (bytesRead > 0) {
buffer[bytesRead] = '\0';
bufferFree -= (bytesRead + 1);
if (bufferFree == 0) {
bufferSize += bufferFree = BUFFER_SIZE;
buffer = realloc(buffer, bufferSize);
}
for (idx = 0; idx < sizeof(responseCodes) / sizeof(*responseCodes);
idx++) {
if (strstr(buffer, responseCodes[idx])) {
isEnd = 1;
break;
}
}
} else if (bytesRead == 0 && time(NULL) - timeStart > 180) {
printf("Response timeout after 180 seconds\n");
returnCode = 1;
break;
}
}
printf("%s\n", buffer);
free(buffer);
return returnCode;
}
int main() {
char *commandList[] = {"AT", "ATI", "AT+COPS?"/* ,
"AT+COPS=?" */},
serialFilePath[] = "/dev/serial0";
int serialPort;
unsigned long idx;
serialPort = openSerialPort(serialFilePath);
if (serialPort < 0) {
printf("Error openSerialPort()\n");
return 1;
}
for (idx = 0; idx < sizeof(commandList) / sizeof(*commandList); idx++) {
if (0 != querySerialPort(serialPort, commandList[idx])) {
printf("Error querySerialPort()\n");
close(serialPort);
return 1;
}
}
close(serialPort);
return 0;
}
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