[SX126x/SX128x] Start reading from Rx buffer offset

src/modules/SX126x/SX126x.cpp

@@ -709,20 +709,17 @@ int16_t SX126x::readData(uint8_t* data, size_t len) {
   if((irq & RADIOLIB_SX126X_IRQ_CRC_ERR) || (irq & RADIOLIB_SX126X_IRQ_HEADER_ERR)) {
     crcState = RADIOLIB_ERR_CRC_MISMATCH;
   }
-
-  // get packet length
-  size_t length = getPacketLength();
+
+  // get packet length and Rx buffer offset
+  uint8_t offset = 0;
+  size_t length = getPacketLength(true, &offset);
   if((len != 0) && (len < length)) {
     // user requested less data than we got, only return what was requested
     length = len;
   }
 
-  // read packet data
-  state = readBuffer(data, length);
-  RADIOLIB_ASSERT(state);
-
-  // reset the base addresses
-  state = setBufferBaseAddress();
+  // read packet data starting at offset
+  state = readBuffer(data, length, offset);
   RADIOLIB_ASSERT(state);
 
   // clear interrupt flags
@@ -1394,6 +1391,10 @@ float SX126x::getFrequencyError() {
 }
 
 size_t SX126x::getPacketLength(bool update) {
+  return(this->getPacketLength(update, NULL));
+}
+
+size_t SX126x::getPacketLength(bool update, uint8_t* offset) {
   (void)update;
 
   // in implicit mode, return the cached value
@@ -1403,6 +1404,9 @@ size_t SX126x::getPacketLength(bool update) {
 
   uint8_t rxBufStatus[2] = {0, 0};
   this->mod->SPIreadStream(RADIOLIB_SX126X_CMD_GET_RX_BUFFER_STATUS, rxBufStatus, 2);
+
+  if(offset) { *offset = rxBufStatus[1]; }
+
   return((size_t)rxBufStatus[0]);
 }
 

src/modules/SX126x/SX126x.h

@@ -952,6 +952,14 @@ class SX126x: public PhysicalLayer {
     */
     size_t getPacketLength(bool update = true) override;
 
+    /*!
+      \brief Query modem for the packet length of received payload and Rx buffer offset.
+      \param update Update received packet length. Will return cached value when set to false.
+      \param offset Pointer to variable to store the Rx buffer offset.
+      \returns Length of last received packet in bytes.
+    */
+    size_t getPacketLength(bool update, uint8_t* offset);
+
     /*!
       \brief Set modem in fixed packet length mode. Available in FSK mode only.
       \param len Packet length.

src/modules/SX128x/SX128x.cpp

@@ -617,15 +617,16 @@ int16_t SX128x::readData(uint8_t* data, size_t len) {
     crcState = RADIOLIB_ERR_CRC_MISMATCH;
   }
 
-  // get packet length
-  size_t length = getPacketLength();
+  // get packet length and Rx buffer offset
+  uint8_t offset = 0;
+  size_t length = getPacketLength(true, &offset);
   if((len != 0) && (len < length)) {
     // user requested less data than we got, only return what was requested
     length = len;
   }
 
-  // read packet data
-  state = readBuffer(data, length);
+  // read packet data starting at offset 
+  state = readBuffer(data, length, offset);
   RADIOLIB_ASSERT(state);
 
   // clear interrupt flags
@@ -1253,6 +1254,10 @@ float SX128x::getFrequencyError() {
 }
 
 size_t SX128x::getPacketLength(bool update) {
+  return(this->getPacketLength(update, NULL));
+}
+
+size_t SX128x::getPacketLength(bool update, uint8_t* offset) {
   (void)update;
 
   // in implicit mode, return the cached value
@@ -1262,6 +1267,9 @@ size_t SX128x::getPacketLength(bool update) {
 
   uint8_t rxBufStatus[2] = {0, 0};
   this->mod->SPIreadStream(RADIOLIB_SX128X_CMD_GET_RX_BUFFER_STATUS, rxBufStatus, 2);
+
+  if(offset) { *offset = rxBufStatus[1]; }
+
   return((size_t)rxBufStatus[0]);
 }
 
@@ -1412,8 +1420,8 @@ int16_t SX128x::writeBuffer(uint8_t* data, uint8_t numBytes, uint8_t offset) {
   return(this->mod->SPIwriteStream(cmd, 2, data, numBytes));
 }
 
-int16_t SX128x::readBuffer(uint8_t* data, uint8_t numBytes) {
-  uint8_t cmd[] = { RADIOLIB_SX128X_CMD_READ_BUFFER, RADIOLIB_SX128X_CMD_NOP };
+int16_t SX128x::readBuffer(uint8_t* data, uint8_t numBytes, uint8_t offset) {
+  uint8_t cmd[] = { RADIOLIB_SX128X_CMD_READ_BUFFER, offset };
   return(this->mod->SPIreadStream(cmd, 2, data, numBytes));
 }
 

src/modules/SX128x/SX128x.h

@@ -745,6 +745,14 @@ class SX128x: public PhysicalLayer {
     */
     size_t getPacketLength(bool update = true) override;
 
+    /*!
+      \brief Query modem for the packet length of received payload and Rx buffer offset.
+      \param update Update received packet length. Will return cached value when set to false.
+      \param offset Pointer to variable to store the Rx buffer offset.
+      \returns Length of last received packet in bytes.
+    */
+    size_t getPacketLength(bool update, uint8_t* offset);
+
     /*!
       \brief Get expected time-on-air for a given size of payload.
       \param len Payload length in bytes.
@@ -820,7 +828,7 @@ class SX128x: public PhysicalLayer {
     int16_t writeRegister(uint16_t addr, uint8_t* data, uint8_t numBytes);
     int16_t readRegister(uint16_t addr, uint8_t* data, uint8_t numBytes);
     int16_t writeBuffer(uint8_t* data, uint8_t numBytes, uint8_t offset = 0x00);
-    int16_t readBuffer(uint8_t* data, uint8_t numBytes);
+    int16_t readBuffer(uint8_t* data, uint8_t numBytes, uint8_t offset = 0x00);
     int16_t setTx(uint16_t periodBaseCount = RADIOLIB_SX128X_TX_TIMEOUT_NONE, uint8_t periodBase = RADIOLIB_SX128X_PERIOD_BASE_15_625_US);
     int16_t setRx(uint16_t periodBaseCount, uint8_t periodBase = RADIOLIB_SX128X_PERIOD_BASE_15_625_US);
     int16_t setCad();