An ESP8266/Arduino library for communicating with the AI-Thinker A6 GSM module. It will probably also work with other GSM modules that use the AT command set, like the SIM900.
This library is an adaptation of this sample module. It is still very incomplete, but at least it works somewhat. Please feel free to issue pull requests to improve it.
If you have the A6 breakout board, connect the Tx and Rx pins to your ESP8266. The example assumes the TX pin is connected to D5 and the RX to D6. A6lib can power-cycle the module if you connect a MOSFET to a pin and control the A6's power supply with it.
The A6's PWR pin should be permanently connected to Vcc (if you think that's wrong or know a better way, please open an issue).
The code looks something like this:
// Instantiate the class with Tx, Rx (remember to swap them when connecting to
the A6, i.e. connect the A6's Rx pin to D6).
A6 A6c(D6, D5);
// Initialize the modem, rebooting it if it fails to become ready.
do {
// Power-cycle the module to reset it.
A6c.powerCycle(D0);
} while (A6c.blockUntilReady(9600) != A6_OK);
// Start and place a call.
A6c.dial("1234567890");
delay(8000);
A6c.hangUp();
delay(8000);
A6c.redial();
delay(8000);
// Send a message.
A6c.sendSMS("+1234567890", "Hello there!");
// Get an SMS message from memory.
SMSmessage sms = A6c.readSMS(3);
// Delete an SMS message.
A6c.deleteSMS(3);
callInfo cinfo = A6c.checkCallStatus();
// This will be the calling number, "1234567890".
cinfo.number;