A6 A7 gateway (GSM GPRS) (#195)

* init 2G gateway with SMS sending and receiving

* A6lib add

* add 2Ggateway call from setup and loop

* add schematic and image

lib/A6lib/examples/dial/dial.ino

@@ -0,0 +1,44 @@
+#include <A6lib.h>
+
+#ifndef ESP8266
+#define D0 0
+#define D5 8
+#define D6 7
+#endif
+
+// Instantiate the library with TxPin, RxPin.
+A6lib A6l(D6, D5);
+
+void setup() {
+    Serial.begin(115200);
+
+    delay(1000);
+
+    // Power-cycle the module to reset it.
+    A6l.powerCycle(D0);
+    A6l.blockUntilReady(9600);
+}
+
+void loop() {
+    Serial.println("Checking call status...");
+    callInfo cinfo = A6l.checkCallStatus();
+    Serial.println("Call status checked.");
+
+    int sigStrength = A6l.getSignalStrength();
+    Serial.print("Signal strength percentage: ");
+    Serial.println(sigStrength);
+
+    delay(5000);
+
+    if (cinfo.number != NULL) {
+        if (cinfo.direction == DIR_INCOMING && cinfo.number == "919999999999") {
+            A6l.answer();
+        } else {
+            A6l.hangUp();
+        }
+        delay(1000);
+    } else {
+        Serial.println("No number yet.");
+        delay(1000);
+    }
+}