added documentation on initialisation in ModemInterface

Author: cristidragomir97

Diff for: src/ModemInterface.cpp

@@ -5,28 +5,31 @@
 #include <ModemInterface.h>
 
 #if defined(ARDUINO_PORTENTA_C33)
-    #define ON_PIN 32 // P708 (32) is the ON pin
-
+    // On the C33 the Serial1 object is already defined, but it does not have hardware flow control
+    // mbed allows us to define a UART object with software flow control on given pins 
     // P602/P110/P603/P604 -> Serial1
-    UART Serial1_FC(UART1_TX_PIN, UART1_RX_PIN, 61, 62);
+    UART Serial1_FC(UART1_TX_PIN, UART1_RX_PIN, PORTENTA_C33_CTS_PIN, PORTENTA_C33_RTS_PIN);
 
     #ifdef DUMP_AT_COMMANDS
     StreamDebugger          debugger(Serial1_FC, Serial);
-    __attribute__ ((init_priority (101))) ModemInterface        modem(debugger, ON_PIN);
+    
+    // we need to make sure that the Modem object is initialised before anything else in the sketch to avoid issues with the TinyGSM library
+    // the init_priority attribute is used to set the priority of the constructor, the lower the number the higher the priority (101 to 65535)
+    // for more information see https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html
+    __attribute__ ((init_priority (101))) ModemInterface        modem(debugger, PORTENTA_C33_MODEM_ON_PIN);
     #else
-    __attribute__ ((init_priority (101))) ModemInterface        modem(Serial1_FC, ON_PIN);
+    __attribute__ ((init_priority (101))) ModemInterface        modem(Serial1_FC, PORTENTA_C33_MODEM_ON_PIN);
     #endif
 
 #elif defined(ARDUINO_PORTENTA_H7_M7) || defined(CORE_CM4)
     #include "pinDefinitions.h"
-    #define ON_PIN PG_3 // PG3 is the ON pin
 
     // P602/P110/P603/P604 -> Serial1  
     #ifdef DUMP_AT_COMMANDS
     StreamDebugger          debugger(Serial1, Serial);
-    __attribute__ ((init_priority (101))) ModemInterface modem(debugger, PinNameToIndex(ON_PIN));
+    __attribute__ ((init_priority (101))) ModemInterface modem(debugger, PinNameToIndex(PORTENTA_H7_MODEM_ON_PIN));
     #else
-    __attribute__ ((init_priority (101))) ModemInterface modem(Serial1, PinNameToIndex(ON_PIN));
+    __attribute__ ((init_priority (101))) ModemInterface modem(Serial1, PinNameToIndex(PORTENTA_H7_MODEM_ON_PIN));
     #endif
 
 #endif

Diff for: src/ModemInterface.h

@@ -11,6 +11,14 @@
 #define TINY_GSM_RX_BUFFER 1024
 #define TINY_GSM_MODEM_BG96
 
+#if defined(ARDUINO_PORTENTA_H7_M7) || defined(CORE_CM4)
+  #define PORTENTA_H7_MODEM_ON_PIN PG_3 // PG3 is the ON pin
+#elif defined(ARDUINO_PORTENTA_C33)
+  #define PORTENTA_C33_CTS_PIN 61
+  #define PORTENTA_C33_RTS_PIN 62
+  #define PORTENTA_C33_MODEM_ON_PIN 32
+#endif
+
 
 #include <Arduino.h>
 #include <StreamDebugger.h>
@@ -19,7 +27,7 @@
 
 /**
  * @class ModemInterface
- * @brief Represents the interface to the 4G modem module.
+ * @brief Represents the interface to the 4G modem module which extends the TinyGsmBG96 class.
  */
 class ModemInterface : public TinyGsmBG96 {
 public:
@@ -33,16 +41,20 @@ class ModemInterface : public TinyGsmBG96 {
   };
 
   /**
-   * @brief Initializes the modem interface.
+   * @brief Initializes the modem interface. (Overrides the init method in TinyGsmBG96)
    * @param pin The PIN code for the SIM card (optional).
    * @return True if initialization is successful, false otherwise.
    */
   bool init(const char* pin = NULL) {
+    // Power on the modem
     pinMode(powerPin, OUTPUT);
     digitalWrite(powerPin, HIGH);
     delay(1000);
+
     #ifdef DUMP_AT_COMMANDS
       #if defined(ARDUINO_PORTENTA_C33)
+        // On the C33 we have defined a UART object with software flow control on given pins in the .cpp file, we'll use extern to access and begin communication
+
         extern UART Serial1_FC;
         Serial1_FC.begin(115200);
       #endif