GSM: add setTimeout function

libraries/GSM/src/GSM.cpp

@@ -68,6 +68,7 @@ int arduino::GSMClass::begin(const char* pin, const char* apn, const char* usern
 
   _device->set_cmux_status_flag(_cmuxGSMenable);
   _device->set_retry_timeout_array(_retry_timeout, sizeof(_retry_timeout) / sizeof(_retry_timeout[0]));
+  _device->set_timeout(_timeout);
   _device->attach(mbed::callback(this, &GSMClass::onStatusChange));
   _device->init();
 
@@ -101,6 +102,10 @@ int arduino::GSMClass::begin(const char* pin, const char* apn, const char* usern
   return connect_status == NSAPI_ERROR_OK ? 1 : 0;
 }
 
+void arduino::GSMClass::setTimeout(unsigned long timeout) {
+  _timeout = timeout;
+}
+
 void arduino::GSMClass::enableCmux() {
   _cmuxGSMenable = true;
 }

libraries/GSM/src/GSM.h

@@ -100,8 +100,12 @@ class GSMClass : public MbedSocketClass {
    */
   void end(void);
 
-  unsigned long getTime();
+  /*
+   * Change cellular state timeouts. Needs to be called before GSM.begin()
+   */
+  void setTimeout(unsigned long timeout);
 
+  unsigned long getTime();
   unsigned long getLocalTime();
 
   bool setTime(unsigned long const epoch, int const timezone = 0);
@@ -133,6 +137,7 @@ class GSMClass : public MbedSocketClass {
   mbed::CellularContext* _context = nullptr;
   mbed::CellularDevice* _device = nullptr;
   bool _at_debug = false;
+  unsigned long _timeout = 1000;
 
   /* Internal cellular state machine retries. Values are in seconds.
    * This array also defines the maximum number of retries to CELLULAR_RETRY_ARRAY_SIZE