1 files changed, 142 insertions, 0 deletions
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..c041563
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,142 @@
+#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;
+}