Ensures ES8266 firmware version up to date

If ESP8266 firmware version is less that v2.0.0, then we print a debug
message and return an error from the connect function.

Author: sarahmarshy

ESP8266/ESP8266.cpp

@@ -24,6 +24,14 @@ ESP8266::ESP8266(PinName tx, PinName rx, bool debug)
     _parser.debugOn(debug);
 }
 
+bool ESP8266::check_firmware_version()
+{
+    _parser.send("AT+GMR");
+    int8_t version = 0;
+    bool success = _parser.recv("SDK version: %d", &version) && _parser.recv("OK");
+    return success && (version == 2);
+}
+
 bool ESP8266::startup(int mode)
 {
     //only 3 valid modes

ESP8266/ESP8266.h

@@ -27,6 +27,13 @@ class ESP8266
 public:
     ESP8266(PinName tx, PinName rx, bool debug=false);
 
+    /**
+    * Check firmware version of ESP8266
+    *
+    * @return true only if ESP8266 firmware > v2
+    */
+    bool check_firmware_version(void);
+    
     /**
     * Startup the ESP8266
     *

ESP8266Interface.cpp

@@ -46,8 +46,16 @@ int ESP8266Interface::connect(const char *ssid, const char *pass, nsapi_security
 
 int ESP8266Interface::connect()
 {
+    _esp.setTimeout(ESP8266_MISC_TIMEOUT);
+    
+    if(!_esp.check_firmware_version()) {
+        debug("ERROR: Firmware incompatible with this driver.\
+               \r\nUpdate to v2.0.0 - https://developer.mbed.org/teams/ESP8266/wiki/Firmware-Update\r\n"); 
+        return NSAPI_ERROR_DEVICE_ERROR;
+    }
+    
     _esp.setTimeout(ESP8266_CONNECT_TIMEOUT);
-
+  
     if (!_esp.startup(3)) {
         return NSAPI_ERROR_DEVICE_ERROR;
     }

ESP8266Interface.h

@@ -18,6 +18,7 @@
 #define ESP8266_INTERFACE_H
 
 #include "mbed.h"
+#include "mbed_debug.h"
 #include "ESP8266.h"