SIM900A not sending sms

Projects Programming
19

I found a mistake in my sketch. I had accidentally turned "CMGW" into "CMGS" and I also left out the "CMSS" which does the actual send. One problem is that the CMSS command needs to know what SMS memory location was set by CMGW. I added code to "WaitForReply" that grabs the number reported by CMGW and then I can use that when sending "AT+CMSS: n".

Try this new version:

#include <SoftwareSerial.h>

SoftwareSerial ATCommandStream(2, 3);
// Connect the ATCommandStream TX to Arduino pin 2 RX.
// Connect the ATCommandStream RX to Arduino pin 3 TX.

const char * number = "+639358861057";
int MemoryWriteLocation = 1;

void setup()
{
  // start th serial communication with the host computer
  Serial.begin(19200);
  while (!Serial);
  Serial.println("Arduino with ATCommandStream is ready");
  // start communication with the ATCommandStream in 19200
  ATCommandStream.begin(19200);
  Serial.println("ATCommandStream started at 19200");
  delay(1000);
  Serial.println("Setup Complete! ATCommandStream is Ready!");

  // Turn on verbose messages
  SendShortCommand("AT+CMEE");

  // Set character set to GSM:
  SendShortCommand("AT+CSCS=\"GSM\"");

  // Set the SMS output to text mode
  SendShortCommand("AT+CMGF=1");

  // Check the phone number type
  SendShortCommand("AT+CSTA?");
  Serial.println("Note: 129=Unknown, 161=National, 145=International, 177=Network Specific");

  // Test for CMGS command support:
  SendShortCommand("AT+CMGS=?");
}

void loop()
{
  // Keep reading from SIM900 and send to Arduino Serial Monitor
  if (ATCommandStream.available())
  {
    char c = ATCommandStream.read();
    Serial.write(c);
  }

  // Keep reading from Arduino Serial Monitor and send to ATCommandStream
  if (Serial.available())
  {
    char c = Serial.read();
    if (c == 's')
    {
      SendSMSMessage(number, "sim900a sms");
    }
  }
}

bool WaitForResponse()
{
  unsigned long startTime = millis();
  while (millis() - startTime < 5000)
  {
    String reply = ATCommandStream.readStringUntil('\n');
    if (reply.length() > 0)
    {
      Serial.print("Received: \"");
      Serial.print(reply);
      Serial.println("\"");
      if (reply.startsWith("+CMGW:"))
      {
        reply.remove(0, 6); // Strip off "+CMGW:"
        MemoryWriteLocation = reply.toInt();
      }
      if (reply.startsWith("OK"))
        return true;
      if (reply.startsWith("ERROR"))
        return false;
    }
  }
  Serial.println("Did not receive OK.");
  return false;
}

bool SendShortCommand(String command)
{
  Serial.print("Sending command: \"");
  Serial.print(command);
  Serial.println("\"");

  ATCommandStream.print(command);
  ATCommandStream.print("\r\n");

  return WaitForResponse();
}

void SendSMSMessage(const char *number, const char *message)
{
  Serial.println("Sending SMS text followed by Ctrl-Z/ESC");
  
  Serial.print("Sending: ");
  Serial.print("AT+CMGW=\"");
  Serial.print(number);
  Serial.println("\"(CR)");
  Serial.print(message); // The SMS text you want to send
  Serial.println("(ESC)");


  ATCommandStream.print("AT+CMGW=\"");  // Write message to memory
  ATCommandStream.print(number);
  ATCommandStream.print("\"\r"); // NOTE: Command ends with CR, not CRLF
  ATCommandStream.print(message); // The SMS text you want to send
  ATCommandStream.write(26); // ASCII code of CTRL+Z

  WaitForResponse();

  String command = "AT+CMSS=" + String(MemoryWriteLocation);
  SendShortCommand(command);  // Send message in memory location 1
}