Make processRTCMframe weak

Allow processRTCMframe to be overridden.  Its replacement would now be
able to place all of the bytes into a buffer for processing at a later
time and eliminate a deep call stack for every byte.

src/SparkFun_u-blox_GNSS_Arduino_Library.cpp

@@ -2114,7 +2114,7 @@ void SFE_UBLOX_GNSS::process(uint8_t incoming, ubxPacket *incomingUBX, uint8_t r
   }
   else if (currentSentence == RTCM)
   {
-    processRTCMframe(incoming); // Deal with RTCM bytes
+    currentSentence = processRTCMframe(incoming, &rtcmFrameCounter); // Deal with RTCM bytes
   }
 }
 
@@ -2876,13 +2876,15 @@ nmeaAutomaticFlags *SFE_UBLOX_GNSS::getNMEAFlagsPtr()
 // Byte 2: 10-bits of length of this packet including the first two-ish header bytes, + 6.
 // byte 3 + 4 bits: Msg type 12 bits
 // Example: D3 00 7C 43 F0 ... / 0x7C = 124+6 = 130 bytes in this packet, 0x43F = Msg type 1087
-void SFE_UBLOX_GNSS::processRTCMframe(uint8_t incoming)
+SFE_UBLOX_GNSS::SentenceTypes SFE_UBLOX_GNSS::processRTCMframe(uint8_t incoming, uint16_t * rtcmFrameCounter)
 {
-  if (rtcmFrameCounter == 1)
+  static uint16_t rtcmLen = 0;
+
+  if (*rtcmFrameCounter == 1)
   {
     rtcmLen = (incoming & 0x03) << 8; // Get the last two bits of this byte. Bits 8&9 of 10-bit length
   }
-  else if (rtcmFrameCounter == 2)
+  else if (*rtcmFrameCounter == 2)
   {
     rtcmLen |= incoming; // Bits 0-7 of packet length
     rtcmLen += 6;        // There are 6 additional bytes of what we presume is header, msgType, CRC, and stuff
@@ -2896,15 +2898,12 @@ void SFE_UBLOX_GNSS::processRTCMframe(uint8_t incoming)
     rtcmMsgType |= (incoming >> 4); //Message Type, bits 0-7
   }*/
 
-  rtcmFrameCounter++;
+  *rtcmFrameCounter++;
 
   processRTCM(incoming); // Here is where we expose this byte to the user
 
-  if (rtcmFrameCounter == rtcmLen)
-  {
-    // We're done!
-    currentSentence = NONE; // Reset and start looking for next sentence type
-  }
+  // Reset and start looking for next sentence type when done
+  return (*rtcmFrameCounter == rtcmLen) ? NONE : RTCM;
 }
 
 // This function is called for each byte of an RTCM frame

src/SparkFun_u-blox_GNSS_Arduino_Library.h

@@ -646,6 +646,15 @@ public:
   SFE_UBLOX_GNSS(void);
   ~SFE_UBLOX_GNSS(void);
 
+  // Depending on the sentence type the processor will load characters into different arrays
+  enum SentenceTypes
+  {
+    NONE = 0,
+    NMEA,
+    UBX,
+    RTCM
+  } currentSentence = NONE;
+
 // A default of 250ms for maxWait seems fine for I2C but is not enough for SerialUSB.
 // If you know you are only going to be using I2C / Qwiic communication, you can
 // safely reduce defaultMaxWait to 250.
@@ -738,7 +747,7 @@ public:
 
   void process(uint8_t incoming, ubxPacket *incomingUBX, uint8_t requestedClass, uint8_t requestedID);    // Processes NMEA and UBX binary sentences one byte at a time
   void processNMEA(char incoming) __attribute__((weak));                                                  // Given a NMEA character, do something with it. User can overwrite if desired to use something like tinyGPS or MicroNMEA libraries
-  void processRTCMframe(uint8_t incoming);                                                                // Monitor the incoming bytes for start and length bytes
+  SentenceTypes processRTCMframe(uint8_t incoming, uint16_t * rtcmFrameCounter) __attribute__((weak));    // Monitor the incoming bytes for start and length bytes
   void processRTCM(uint8_t incoming) __attribute__((weak));                                               // Given rtcm byte, do something with it. User can overwrite if desired to pipe bytes to radio, internet, etc.
   void processUBX(uint8_t incoming, ubxPacket *incomingUBX, uint8_t requestedClass, uint8_t requestedID); // Given a character, file it away into the uxb packet structure
   void processUBXpacket(ubxPacket *msg);                                                                  // Once a packet has been received and validated, identify this packet's class/id and update internal flags
@@ -1582,15 +1591,6 @@ public:
   uint16_t rtcmFrameCounter = 0; // Tracks the type of incoming byte inside RTCM frame
 
 private:
-  // Depending on the sentence type the processor will load characters into different arrays
-  enum SentenceTypes
-  {
-    NONE = 0,
-    NMEA,
-    UBX,
-    RTCM
-  } currentSentence = NONE;
-
   // Depending on the ubx binary response class, store binary responses into different places
   enum classTypes
   {
@@ -1761,8 +1761,6 @@ private:
   uint8_t getNMEAMaxLength();            // Get the maximum length of this NMEA message
   nmeaAutomaticFlags *getNMEAFlagsPtr(); // Get a pointer to the flags
 
-  uint16_t rtcmLen = 0;
-
   // Flag to prevent reentry into checkCallbacks
   // Prevent badness if the user accidentally calls checkCallbacks from inside a callback
   volatile bool checkCallbacksReentrant = false;