[Si443x] Added fixed packet length mode

src/modules/Si443x/Si443x.cpp

@@ -61,6 +61,8 @@ int16_t Si443x::begin(float br, float freqDev, float rxBw, uint8_t preambleLen)
   state = setEncoding(0);
   RADIOLIB_ASSERT(state);
 
+  state = variablePacketLengthMode();
+
   return(state);
 }
 
@@ -233,8 +235,9 @@ int16_t Si443x::startTransmit(uint8_t* data, size_t len, uint8_t addr) {
   clearIRQFlags();
 
   // set packet length
-  /// \todo variable packet length
+  if (_packetLengthConfig == RADIOLIB_SI443X_FIXED_PACKET_LENGTH_OFF) {
     _mod->SPIwriteRegister(RADIOLIB_SI443X_REG_TRANSMIT_PACKET_LENGTH, len);
+  }
 
   /// \todo use header as address field?
   (void)addr;
@@ -591,6 +594,14 @@ void Si443x::readBit(RADIOLIB_PIN_TYPE pin) {
   updateDirectBuffer((uint8_t)digitalRead(pin));
 }
 
+int16_t Si443x::fixedPacketLengthMode(uint8_t len) {
+  return(Si443x::setPacketMode(RADIOLIB_SI443X_FIXED_PACKET_LENGTH_ON, len));
+}
+
+int16_t Si443x::variablePacketLengthMode(uint8_t maxLen) {
+  return(Si443x::setPacketMode(RADIOLIB_SI443X_FIXED_PACKET_LENGTH_OFF, maxLen));
+}
+
 int16_t Si443x::setFrequencyRaw(float newFreq) {
   // set mode to standby
   int16_t state = standby();
@@ -619,6 +630,25 @@ int16_t Si443x::setFrequencyRaw(float newFreq) {
   return(state);
 }
 
+int16_t Si443x::setPacketMode(uint8_t mode, uint8_t len) {
+  // check packet length
+  if (len > RADIOLIB_SI443X_MAX_PACKET_LENGTH) {
+    return(RADIOLIB_ERR_PACKET_TOO_LONG);
+  }
+
+  // set to fixed packet length
+  int16_t state = _mod->SPIsetRegValue(RADIOLIB_SI443X_REG_HEADER_CONTROL_2, mode, 3, 3);
+  RADIOLIB_ASSERT(state);
+
+  // set length to register
+  state = _mod->SPIsetRegValue(RADIOLIB_SI443X_REG_TRANSMIT_PACKET_LENGTH, len);
+  RADIOLIB_ASSERT(state);
+
+  // update cached value
+  _packetLengthConfig = mode;
+  return(state);
+}
+
 bool Si443x::findChip() {
   uint8_t i = 0;
   bool flagFound = false;

src/modules/Si443x/Si443x.h

@@ -816,6 +816,24 @@ class Si443x: public PhysicalLayer {
     */
     void readBit(RADIOLIB_PIN_TYPE pin);
 
+    /*!
+     \brief Set modem in fixed packet length mode.
+
+     \param len Packet length.
+
+     \returns \ref status_codes
+   */
+   int16_t fixedPacketLengthMode(uint8_t len = RADIOLIB_SI443X_MAX_PACKET_LENGTH);
+
+    /*!
+     \brief Set modem in variable packet length mode.
+
+     \param len Maximum packet length.
+
+     \returns \ref status_codes
+   */
+   int16_t variablePacketLengthMode(uint8_t maxLen = RADIOLIB_SI443X_MAX_PACKET_LENGTH);
+
 #if !defined(RADIOLIB_GODMODE) && !defined(RADIOLIB_LOW_LEVEL)
   protected:
 #endif
@@ -831,8 +849,10 @@ class Si443x: public PhysicalLayer {
 
     size_t _packetLength = 0;
     bool _packetLengthQueried = false;
+    uint8_t _packetLengthConfig = RADIOLIB_SI443X_FIXED_PACKET_LENGTH_ON;
 
     int16_t setFrequencyRaw(float newFreq);
+    int16_t setPacketMode(uint8_t mode, uint8_t len);
 
 #if !defined(RADIOLIB_GODMODE)
   private: