SX1262: Does enabling setRxBoostedGainMode increase the RSSI value for FSK reception #1232

Celliwig · 2024-09-24T10:51:27Z

Celliwig
Sep 24, 2024

Hi,

I'm hoping that somebody can put me out of my misery on this one.

Have an SX1262 setup to receive FSK packets, no problem. However noticed that the RSSI for the packets was substantially lower (10-20 db) in comparison to a sx1276 that I also have setup. Having done some Googling saw some mention of a similar situation and it being resolved by enabling Rx Boosted Gain. Having included that in my code I found it made absolutely no difference. I checked my code, and it's looks like it's writing the correct values to the registers, read back the register and it is also what I expect...

Should I expect Rx Boosted Gain to increase the RSSI for FSK packets, or am I being a moron...

Thanks for any input.

StevenCellist · 2024-09-24T12:07:08Z

StevenCellist
Sep 24, 2024
Collaborator

I cannot answer the question (for that we must summon @jgromes the Great), but I do have a question for you to answer in the meantime: what is your transmission source? Is it another SX1276, or an SX1262, or something else (if so, what is it)?

2 replies

Celliwig Sep 24, 2024
Author

Primarily using another sx1276. (Do have another sx1262 but haven't tried that yet, doing this remotely which complicates
matters...)

jgromes Sep 24, 2024
Maintainer

I have been summoned - who dares disturb my slumber?!?

The SX1262 datasheet specifies sensitivity for Rx boosted gain for FSK as well as LoRa, so it should work for both. However, the difference in sensitivity is only 3 dB at 4k8 FSK (see below). 10-20 dB seems like way too much to be explained just by that. Could you share your code just so that we can check any obvious issues? Also some information about the hardware setup would be useful; for example, are you sure you have correctly tuned antenna for the SX126x?

Celliwig · 2024-09-24T23:15:12Z

Celliwig
Sep 24, 2024
Author

Hi, sorry to disturb your slumber 😉

The original code is not suitable for sharing, but knocked up a reasonable facsimile using the FSK modem example. The sender is a Lillygo TTGO (ESP32 WROOM with a sx1276). The receiver is a custom board which has a few Waveshare Core1262 modules on it, connected to an ESP32 WROOM. These modules are connected together on a shared bus, with different chip select lines selecting for each one. The CS lines are inverted, so have (crudely...) altered the RadioLib library to account for that (can't for the life of me imagine how that could affect things).

So here's the sender code:

// include the library
#include <RadioLib.h>

#define SERIAL_BAUDRATE 4000000

// Lilygo TTGO (SX1276)
////////////////////////////////////////
// SPI clock frequency
#define RADIO_SPI_SCK_FREQ 			10000000
// Pins used by the radio transceiver module
#define RADIO_SPI_SCK 				5
#define RADIO_SPI_MISO 				19
#define RADIO_SPI_MOSI 				27
#define RADIO_SPI_CS 				18
#define RADIO_SPI_RST 				23
#define RADIO_SPI_IRQ 				26

// FSK configuration
////////////////////////////////////////
#define FSK_CFG_TX_PWR 				2

#define FSK_CFG_BAND 				869.8

// Bit rate: 19.2k
#define FSK_CFG_BIT_RATE			19.2
#define FSK_CFG_FREQUENCY_DEVIATION		20
#define FSK_CFG_RX_BANDWIDTH			50

#define FSK_CFG_PREAMBLE_LEN			16
#define FSK_CFG_SYNC_WORD			{ 'H', 'L', 'P' }
#define FSK_CFG_SYNC_WORD_LEN			3
#define FSK_CFG_RSSI_SAMPLES			1
#define FSK_CFG_ENCODING			RADIOLIB_ENCODING_WHITENING
#define FSK_CFG_DATA_SHAPING			RADIOLIB_SHAPING_0_5

SX1276 radio = new Module(RADIO_SPI_CS, RADIO_SPI_IRQ, RADIO_SPI_RST);

void setup() {
  Serial.begin(SERIAL_BAUDRATE);

  // Setup for radio module hardware
  SPI.begin(RADIO_SPI_SCK, RADIO_SPI_MISO, RADIO_SPI_MOSI, RADIO_SPI_CS);
  // Set SPI bus frequency
  SPI.setFrequency(RADIO_SPI_SCK_FREQ);

  // initialize SX1276 FSK modem with default settings
  Serial.print(F("[SX1276] Initializing ... "));
  int state = radio.beginFSK();
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);
    while (true);
  }

  // Select FSK, not OOK
  if (radio.setOOK(false) != RADIOLIB_ERR_NONE) {
    Serial.println("  Error initialising radio module: failed to select FSK mode");
    while (true);
  }

  // Configure FSK transceiver module
  if (radio.setFrequency(FSK_CFG_BAND) == RADIOLIB_ERR_INVALID_FREQUENCY) {
    Serial.println("	Error initialising radio module: invalid frequency");
    while (true);
  }
  if (radio.setBitRate(FSK_CFG_BIT_RATE) == RADIOLIB_ERR_INVALID_BIT_RATE) {
    Serial.println("	Error initialising radio module: invalid bit rate");
    while (true);
  }
  if (radio.setFrequencyDeviation(FSK_CFG_FREQUENCY_DEVIATION) == RADIOLIB_ERR_INVALID_FREQUENCY_DEVIATION) {
    Serial.println("	Error initialising radio module: invalid frequency deviation");
    while (true);
  }
  if (radio.setAFCBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid AFC Rx bandwidth");
    while (true);
  }
  if (radio.setRxBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid Rx bandwidth");
    while (true);
  }
  if (radio.setPreambleLength(FSK_CFG_PREAMBLE_LEN) == RADIOLIB_ERR_INVALID_PREAMBLE_LENGTH) {
    Serial.println("	Error initialising radio module: invalid preamble length");
    while (true);
  }
  uint8_t sync_word[] = FSK_CFG_SYNC_WORD;
  if (radio.setSyncWord(sync_word, FSK_CFG_SYNC_WORD_LEN) != RADIOLIB_ERR_NONE) {
    Serial.println("	Error initialising radio module: invalid sync word");
    while (true);
  }
  if (radio.setRSSIConfig(FSK_CFG_RSSI_SAMPLES) == RADIOLIB_ERR_INVALID_NUM_SAMPLES) {
    Serial.println("	Error initialising radio module: invalid RSSI sample average");
    while (true);
  }
  if (radio.setEncoding(FSK_CFG_ENCODING) == RADIOLIB_ERR_INVALID_ENCODING) {
    Serial.println("	Error initialising radio module: invalid encoding scheme");
    while (true);
  }
  if (radio.setDataShaping(FSK_CFG_DATA_SHAPING) == RADIOLIB_ERR_INVALID_DATA_SHAPING) {
    Serial.println("	Error initialising radio module: invalid data shaping");
    while (true);
  }

  if (radio.setOutputPower(FSK_CFG_TX_PWR, false) == RADIOLIB_ERR_INVALID_OUTPUT_POWER) {
    Serial.println("	Error initialising radio module: invalid output power");
    while (true);
  }

  // Disable CRC generation
  radio.setCRC(false);
}

void loop() {
  // FSK modem can use the same transmit/receive methods
  // as the LoRa modem, even their interrupt-driven versions
  // NOTE: FSK modem maximum packet length is 63 bytes!

  // transmit FSK packet
  int state = radio.transmit("Hello World!");
  /*
    byte byteArr[] = {0x01, 0x23, 0x45, 0x67,
                      0x89, 0xAB, 0xCD, 0xEF};
    int state = radio.transmit(byteArr, 8);
  */
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("[SX1276] Packet transmitted successfully!"));
  } else if (state == RADIOLIB_ERR_PACKET_TOO_LONG) {
    Serial.println(F("[SX1276] Packet too long!"));
  } else if (state == RADIOLIB_ERR_TX_TIMEOUT) {
    Serial.println(F("[SX1276] Timed out while transmitting!"));
  } else {
    Serial.println(F("[SX1276] Failed to transmit packet, code "));
    Serial.println(state);
  }

//  // receive FSK packet
//  String str;
//  state = radio.receive(str);
//  /*
//    byte byteArr[8];
//    int state = radio.receive(byteArr, 8);
//  */
//  if (state == RADIOLIB_ERR_NONE) {
//    Serial.println(F("[SX1278] Received packet!"));
//    Serial.print(F("[SX1278] Data:\t"));
//    Serial.println(str);
//  } else if (state == RADIOLIB_ERR_RX_TIMEOUT) {
//    Serial.println(F("[SX1278] Timed out while waiting for packet!"));
//  } else {
//    Serial.println(F("[SX1278] Failed to receive packet, code "));
//    Serial.println(state);
//  }

  delay(1000);
}

The receiver code:

// The chip select lines on this board are 'weird'
// So the library has been updated to reflect this
// So need this
#define RADIOLIB_GODMODE true

// include the library
#include <RadioLib.h>

// Serial baudrate
#define SERIAL_BAUDRATE 1000000

// ESP32 WROOM / Waveshare Core1262
////////////////////////////////////////
// SPI clock frequency
#define RADIO_SPI_SCK_FREQ			10000000
// Pins used by the radio transceiver module
#define RADIO_SPI_SCK				18
#define RADIO_SPI_MISO				19
#define RADIO_SPI_MOSI				23
#define RADIO_SPI_CS				5
#define RADIO_SPI_RST				4
#define RADIO_SPI_IRQ				21
#define RADIO_SPI_BUSY				22
#define SPI_CSEXTRA_X				16
#define SPI_CSEXTRA_Y				17

#define RADIO_TCXO_VLTG				1.8
#define RADIO_TCXO_STRTUP			5000

// FSK configuration
////////////////////////////////////////
#define FSK_CFG_RX_GAIN				false

#define FSK_CFG_BAND				869.8

// Bit rate: 19.2k
#define FSK_CFG_BIT_RATE			19.2
#define FSK_CFG_FREQUENCY_DEVIATION		20
#define FSK_CFG_RX_BANDWIDTH			58.6

#define FSK_CFG_PREAMBLE_LEN			16
#define FSK_CFG_SYNC_WORD			{ 'H', 'L', 'P' }
#define FSK_CFG_SYNC_WORD_LEN			3
#define FSK_CFG_RSSI_SAMPLES			1
#define FSK_CFG_ENCODING			RADIOLIB_ENCODING_WHITENING
#define FSK_CFG_DATA_SHAPING			RADIOLIB_SHAPING_1_0

SX1262 radio = new Module(RADIO_SPI_CS, RADIO_SPI_IRQ, RADIO_SPI_RST, RADIO_SPI_BUSY);

void setup() {
  Serial.begin(SERIAL_BAUDRATE);

  // Invert radio's CS logic
  radio.mod->hal->CsLevelLow = radio.mod->hal->GpioLevelHigh;
  radio.mod->hal->CsLevelHigh = radio.mod->hal->GpioLevelLow;

  // Configure additional SPI CS lines
  pinMode(SPI_CSEXTRA_X, OUTPUT);
  digitalWrite(SPI_CSEXTRA_X, LOW);
  pinMode(SPI_CSEXTRA_Y, OUTPUT);
  digitalWrite(SPI_CSEXTRA_Y, LOW);

  // Setup for radio module hardware
  SPI.begin(RADIO_SPI_SCK, RADIO_SPI_MISO, RADIO_SPI_MOSI, RADIO_SPI_CS);
  // Set SPI bus frequency
  SPI.setFrequency(RADIO_SPI_SCK_FREQ);

  // initialize SX1262 FSK modem with default settings
  Serial.print(F("[SX1262] Initializing ... "));
  int state = radio.beginFSK();
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);
    while (true);
  }

  // Configure TCXO
  if (radio.setTCXO(RADIO_TCXO_VLTG, RADIO_TCXO_STRTUP) != RADIOLIB_ERR_NONE) {
    Serial.println("  Error initialising radio module: failed to configure TCXO");
    while (true);
  }

  // Configure FSK transceiver module
  if (radio.setFrequency(FSK_CFG_BAND) == RADIOLIB_ERR_INVALID_FREQUENCY) {
    Serial.println("	Error initialising radio module: invalid frequency");
    while (true);
  }
  if (radio.setBitRate(FSK_CFG_BIT_RATE) == RADIOLIB_ERR_INVALID_BIT_RATE) {
    Serial.println("	Error initialising radio module: invalid bit rate");
    while (true);
  }
  if (radio.setFrequencyDeviation(FSK_CFG_FREQUENCY_DEVIATION) == RADIOLIB_ERR_INVALID_FREQUENCY_DEVIATION) {
    Serial.println("	Error initialising radio module: invalid frequency deviation");
    while (true);
  }
  if (radio.setRxBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid Rx bandwidth");
    while (true);
  }
  if (radio.setPreambleLength(FSK_CFG_PREAMBLE_LEN) == RADIOLIB_ERR_INVALID_PREAMBLE_LENGTH) {
    Serial.println("	Error initialising radio module: invalid preamble length");
    while (true);
  }
  uint8_t sync_word[] = FSK_CFG_SYNC_WORD;
  if (radio.setSyncWord(sync_word, FSK_CFG_SYNC_WORD_LEN) != RADIOLIB_ERR_NONE) {
    Serial.println("    Error initialising radio module: invalid sync word");
    while (true);
  }
  if (radio.setEncoding(FSK_CFG_ENCODING) == RADIOLIB_ERR_INVALID_ENCODING) {
    Serial.println("	Error initialising radio module: invalid encoding scheme");
    while (true);
  }
  if (radio.setDataShaping(FSK_CFG_DATA_SHAPING) == RADIOLIB_ERR_INVALID_DATA_SHAPING) {
    Serial.println("	Error initialising radio module: invalid data shaping");
    while (true);
  }

  if (radio.setRxBoostedGainMode(FSK_CFG_RX_GAIN, true) != RADIOLIB_ERR_NONE) {
    Serial.println("	Error initialising radio module: invalid gain");
    while (true);
  }

  // Disable CRC generation
  radio.setCRC(false);
}

void loop() {
//  // transmit FSK packet
//  int state = radio.transmit("Hello World!");
//  /*
//    byte byteArr[] = {0x01, 0x23, 0x45, 0x67,
//                      0x89, 0xAB, 0xCD, 0xEF};
//    int state = radio.transmit(byteArr, 8);
//  */
//  if (state == RADIOLIB_ERR_NONE) {
//    Serial.println(F("[SX1262] Packet transmitted successfully!"));
//  } else if (state == RADIOLIB_ERR_PACKET_TOO_LONG) {
//    Serial.println(F("[SX1262] Packet too long!"));
//  } else if (state == RADIOLIB_ERR_TX_TIMEOUT) {
//    Serial.println(F("[SX1262] Timed out while transmitting!"));
//  } else {
//    Serial.println(F("[SX1262] Failed to transmit packet, code "));
//    Serial.println(state);
//  }

  // receive FSK packet
  String str;
  int state = radio.receive(str);
  float rssi = radio.getRSSI(true);
  /*
    byte byteArr[8];
    int state = radio.receive(byteArr, 8);
  */
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("[SX1262] Received packet!"));
    Serial.print(F("[SX1262] Data:\t"));
    Serial.print(str);
    Serial.print("\t\tRSSI: ");
    Serial.println(rssi);
  } else if (state == RADIOLIB_ERR_RX_TIMEOUT) {
    Serial.println(F("[SX1262] Timed out while waiting for packet!"));
  } else {
    Serial.println(F("[SX1262] Failed to receive packet, code "));
    Serial.println(state);
  }

}

Log files of the terminal session, showing average RSSI does not change whether definition 'FSK_CFG_RX_GAIN' is true or false.
RxGainOff.log
RxGainOn.log

As to the antenna, I'm working on this remotely so can't check myself, but I believe the antenna is suitable for the selected frequency.

Thanks for any insights.

1 reply

jgromes Sep 25, 2024
Maintainer

The CS lines are inverted, so have (crudely...) altered the RadioLib library to account for that

Good lord. What about the other GPIO lines, namely the BUSY and IRQ pins, how are those connected? And post a git diff so that we know what changes are we dealing with. Or better yet, override RadioLibHal with a new class based on ArduinoHal that handles the swapped CS logic correctly. There's no need to be digging in the internals.

I believe the antenna is suitable for the selected frequency.

As in "bought as 868 MHz antenna" or "measured as 868 MHz antenna"?

Also, I find it strange how you always have precisely one timeout between receptions, despite the fact that you have a rather fast bit rate and one second between transmissions. You should be seeing loads of timeouts. Change to interrupt reception and add a counter to the sent packets, I have a hunch that you are not actually receiving anything past some initial packet, sicne the RSSI never actually changes.

Celliwig · 2024-09-25T10:51:45Z

Celliwig
Sep 25, 2024
Author

Good lord. What about the other GPIO lines, namely the BUSY and IRQ pins, how are those connected? And post a git diff so that we know what changes are we dealing with. Or better yet, override RadioLibHal with a new class based on ArduinoHal that handles the swapped CS logic correctly. There's no need to be digging in the internals.

BUSY & IRQ are 'normal' hence why I needed to get creative with the CS line. Yep, overriding the HAL would be the way to go long term, but this is a quick and dirty test. I have access (now) to another sx1262 module (LillyGo T3S3) which I can try, but I expect the same results..

As in "bought as 868 MHz antenna" or "measured as 868 MHz antenna"?

Neither. It is designed as an 868 antenna, but I have no way to measure that this end.

As to the dropped packets, if you take a look at the sender code, I added a 1 second delay to the loop (so as not to be spamming the air waves). Here are the logs with that removed:

RxGainOff.nodelay.log
RxGainOn.nodelay.log

0 replies

Celliwig · 2024-09-25T12:14:31Z

Celliwig
Sep 25, 2024
Author

Okay.

To remove any doubts, I swapped out the custom board for a Lillygo T3S3 which has a sx1262 module on it. I also did a completely fresh install of RadioLib to remove any of my 'weirdness'.

Sender code:

// include the library
#include <RadioLib.h>

#define SERIAL_BAUDRATE 4000000

// Lilygo TTGO (SX1276)
////////////////////////////////////////
// SPI clock frequency
#define RADIO_SPI_SCK_FREQ 			10000000
// Pins used by the radio transceiver module
#define RADIO_SPI_SCK 				5
#define RADIO_SPI_MISO 				19
#define RADIO_SPI_MOSI 				27
#define RADIO_SPI_CS 				18
#define RADIO_SPI_RST 				23
#define RADIO_SPI_IRQ 				26

// FSK configuration
////////////////////////////////////////
#define FSK_CFG_TX_PWR 				2

#define FSK_CFG_BAND 				869.8

// Bit rate: 19.2k
#define FSK_CFG_BIT_RATE			19.2
#define FSK_CFG_FREQUENCY_DEVIATION		40
#define FSK_CFG_RX_BANDWIDTH			125.0

#define FSK_CFG_PREAMBLE_LEN			16
#define FSK_CFG_SYNC_WORD			{ 'H', 'L', 'P' }
#define FSK_CFG_SYNC_WORD_LEN			3
#define FSK_CFG_RSSI_SAMPLES			1
#define FSK_CFG_ENCODING			RADIOLIB_ENCODING_WHITENING
#define FSK_CFG_DATA_SHAPING			RADIOLIB_SHAPING_0_5

SX1276 radio = new Module(RADIO_SPI_CS, RADIO_SPI_IRQ, RADIO_SPI_RST);

void setup() {
  Serial.begin(SERIAL_BAUDRATE);

  // Setup for radio module hardware
  SPI.begin(RADIO_SPI_SCK, RADIO_SPI_MISO, RADIO_SPI_MOSI, RADIO_SPI_CS);
  // Set SPI bus frequency
  SPI.setFrequency(RADIO_SPI_SCK_FREQ);

  // initialize SX1276 FSK modem with default settings
  Serial.print(F("[SX1276] Initializing ... "));
  int state = radio.beginFSK();
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);
    while (true);
  }

  // Select FSK, not OOK
  if (radio.setOOK(false) != RADIOLIB_ERR_NONE) {
    Serial.println("  Error initialising radio module: failed to select FSK mode");
    while (true);
  }

  // Configure FSK transceiver module
  if (radio.setFrequency(FSK_CFG_BAND) == RADIOLIB_ERR_INVALID_FREQUENCY) {
    Serial.println("	Error initialising radio module: invalid frequency");
    while (true);
  }
  if (radio.setBitRate(FSK_CFG_BIT_RATE) == RADIOLIB_ERR_INVALID_BIT_RATE) {
    Serial.println("	Error initialising radio module: invalid bit rate");
    while (true);
  }
  if (radio.setFrequencyDeviation(FSK_CFG_FREQUENCY_DEVIATION) == RADIOLIB_ERR_INVALID_FREQUENCY_DEVIATION) {
    Serial.println("	Error initialising radio module: invalid frequency deviation");
    while (true);
  }
  if (radio.setAFCBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid AFC Rx bandwidth");
    while (true);
  }
  if (radio.setRxBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid Rx bandwidth");
    while (true);
  }
  if (radio.setPreambleLength(FSK_CFG_PREAMBLE_LEN) == RADIOLIB_ERR_INVALID_PREAMBLE_LENGTH) {
    Serial.println("	Error initialising radio module: invalid preamble length");
    while (true);
  }
  uint8_t sync_word[] = FSK_CFG_SYNC_WORD;
  if (radio.setSyncWord(sync_word, FSK_CFG_SYNC_WORD_LEN) != RADIOLIB_ERR_NONE) {
    Serial.println("	Error initialising radio module: invalid sync word");
    while (true);
  }
  if (radio.setRSSIConfig(FSK_CFG_RSSI_SAMPLES) == RADIOLIB_ERR_INVALID_NUM_SAMPLES) {
    Serial.println("	Error initialising radio module: invalid RSSI sample average");
    while (true);
  }
  if (radio.setEncoding(FSK_CFG_ENCODING) == RADIOLIB_ERR_INVALID_ENCODING) {
    Serial.println("	Error initialising radio module: invalid encoding scheme");
    while (true);
  }
  if (radio.setDataShaping(FSK_CFG_DATA_SHAPING) == RADIOLIB_ERR_INVALID_DATA_SHAPING) {
    Serial.println("	Error initialising radio module: invalid data shaping");
    while (true);
  }

  if (radio.setOutputPower(FSK_CFG_TX_PWR, false) == RADIOLIB_ERR_INVALID_OUTPUT_POWER) {
    Serial.println("	Error initialising radio module: invalid output power");
    while (true);
  }

  // Disable CRC generation
  radio.setCRC(false);
}

void loop() {
  // FSK modem can use the same transmit/receive methods
  // as the LoRa modem, even their interrupt-driven versions
  // NOTE: FSK modem maximum packet length is 63 bytes!

  // transmit FSK packet
  int state = radio.transmit("Hello World!");
  /*
    byte byteArr[] = {0x01, 0x23, 0x45, 0x67,
                      0x89, 0xAB, 0xCD, 0xEF};
    int state = radio.transmit(byteArr, 8);
  */
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("[SX1276] Packet transmitted successfully!"));
  } else if (state == RADIOLIB_ERR_PACKET_TOO_LONG) {
    Serial.println(F("[SX1276] Packet too long!"));
  } else if (state == RADIOLIB_ERR_TX_TIMEOUT) {
    Serial.println(F("[SX1276] Timed out while transmitting!"));
  } else {
    Serial.println(F("[SX1276] Failed to transmit packet, code "));
    Serial.println(state);
  }

//  // receive FSK packet
//  String str;
//  state = radio.receive(str);
//  /*
//    byte byteArr[8];
//    int state = radio.receive(byteArr, 8);
//  */
//  if (state == RADIOLIB_ERR_NONE) {
//    Serial.println(F("[SX1278] Received packet!"));
//    Serial.print(F("[SX1278] Data:\t"));
//    Serial.println(str);
//  } else if (state == RADIOLIB_ERR_RX_TIMEOUT) {
//    Serial.println(F("[SX1278] Timed out while waiting for packet!"));
//  } else {
//    Serial.println(F("[SX1278] Failed to receive packet, code "));
//    Serial.println(state);
//  }

  //delay(1000);
}

Receiver code:

// include the library
#include <RadioLib.h>

// Serial baudrate
#define SERIAL_BAUDRATE 4000000

// Lilygo T3-S3 (SX1262)
////////////////////////////////////////
// SPI clock frequency
#define RADIO_SPI_SCK_FREQ			18000000
// Pins used by the radio transceiver module
#define RADIO_SPI_SCK				5
#define RADIO_SPI_MISO				3
#define RADIO_SPI_MOSI				6
#define RADIO_SPI_CS				7
#define RADIO_SPI_RST				8
#define RADIO_SPI_IRQ				33
#define RADIO_SPI_BUSY				34
#define RADIO_ANT_RXEN				21
#define RADIO_ANT_TXEN				10

// FSK configuration
////////////////////////////////////////
#define FSK_CFG_RX_GAIN				false

#define FSK_CFG_BAND				869.8

// Bit rate: 19.2k
#define FSK_CFG_BIT_RATE			19.2
#define FSK_CFG_FREQUENCY_DEVIATION		40
#define FSK_CFG_RX_BANDWIDTH			117.3

#define FSK_CFG_PREAMBLE_LEN			16
#define FSK_CFG_SYNC_WORD			{ 'H', 'L', 'P' }
#define FSK_CFG_SYNC_WORD_LEN			3
#define FSK_CFG_RSSI_SAMPLES			1
#define FSK_CFG_ENCODING			RADIOLIB_ENCODING_WHITENING
#define FSK_CFG_DATA_SHAPING			RADIOLIB_SHAPING_1_0

SX1262 radio = new Module(RADIO_SPI_CS, RADIO_SPI_IRQ, RADIO_SPI_RST, RADIO_SPI_BUSY);

void setup() {
  Serial.begin(SERIAL_BAUDRATE);

  // Setup for radio module hardware
  SPI.begin(RADIO_SPI_SCK, RADIO_SPI_MISO, RADIO_SPI_MOSI, RADIO_SPI_CS);
  // Set SPI bus frequency
  SPI.setFrequency(RADIO_SPI_SCK_FREQ);

  // initialize SX1262 FSK modem with default settings
  Serial.print(F("[SX1262] Initializing ... "));
  int state = radio.beginFSK();
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);
    while (true);
  }

//  // Configure TCXO
//  if (radio.setTCXO(RADIO_TCXO_VLTG, RADIO_TCXO_STRTUP) != RADIOLIB_ERR_NONE) {
//    Serial.println("  Error initialising radio module: failed to configure TCXO");
//    while (true);
//  }

  // Configure FSK transceiver module
  if (radio.setFrequency(FSK_CFG_BAND) == RADIOLIB_ERR_INVALID_FREQUENCY) {
    Serial.println("	Error initialising radio module: invalid frequency");
    while (true);
  }
  if (radio.setBitRate(FSK_CFG_BIT_RATE) == RADIOLIB_ERR_INVALID_BIT_RATE) {
    Serial.println("	Error initialising radio module: invalid bit rate");
    while (true);
  }
  if (radio.setFrequencyDeviation(FSK_CFG_FREQUENCY_DEVIATION) == RADIOLIB_ERR_INVALID_FREQUENCY_DEVIATION) {
    Serial.println("	Error initialising radio module: invalid frequency deviation");
    while (true);
  }
  if (radio.setRxBandwidth(FSK_CFG_RX_BANDWIDTH) == RADIOLIB_ERR_INVALID_RX_BANDWIDTH) {
    Serial.println("	Error initialising radio module: invalid Rx bandwidth");
    while (true);
  }
  if (radio.setPreambleLength(FSK_CFG_PREAMBLE_LEN) == RADIOLIB_ERR_INVALID_PREAMBLE_LENGTH) {
    Serial.println("	Error initialising radio module: invalid preamble length");
    while (true);
  }
  uint8_t sync_word[] = FSK_CFG_SYNC_WORD;
  if (radio.setSyncWord(sync_word, FSK_CFG_SYNC_WORD_LEN) != RADIOLIB_ERR_NONE) {
    Serial.println("    Error initialising radio module: invalid sync word");
    while (true);
  }
  if (radio.setEncoding(FSK_CFG_ENCODING) == RADIOLIB_ERR_INVALID_ENCODING) {
    Serial.println("	Error initialising radio module: invalid encoding scheme");
    while (true);
  }
  if (radio.setDataShaping(FSK_CFG_DATA_SHAPING) == RADIOLIB_ERR_INVALID_DATA_SHAPING) {
    Serial.println("	Error initialising radio module: invalid data shaping");
    while (true);
  }

  Serial.print("Rx Gain: ");
  Serial.println(FSK_CFG_RX_GAIN);
  if (radio.setRxBoostedGainMode(FSK_CFG_RX_GAIN, true) != RADIOLIB_ERR_NONE) {
    Serial.println("	Error initialising radio module: invalid gain");
    while (true);
  }

  // Disable CRC generation
  radio.setCRC(false);

  // Set antenna switch pins
  radio.setRfSwitchPins(RADIO_ANT_RXEN, RADIO_ANT_TXEN);
}

void loop() {
//  // transmit FSK packet
//  int state = radio.transmit("Hello World!");
//  /*
//    byte byteArr[] = {0x01, 0x23, 0x45, 0x67,
//                      0x89, 0xAB, 0xCD, 0xEF};
//    int state = radio.transmit(byteArr, 8);
//  */
//  if (state == RADIOLIB_ERR_NONE) {
//    Serial.println(F("[SX1262] Packet transmitted successfully!"));
//  } else if (state == RADIOLIB_ERR_PACKET_TOO_LONG) {
//    Serial.println(F("[SX1262] Packet too long!"));
//  } else if (state == RADIOLIB_ERR_TX_TIMEOUT) {
//    Serial.println(F("[SX1262] Timed out while transmitting!"));
//  } else {
//    Serial.println(F("[SX1262] Failed to transmit packet, code "));
//    Serial.println(state);
//  }

  // receive FSK packet
  String str;
  int state = radio.receive(str);
  float rssi = radio.getRSSI(true);
  /*
    byte byteArr[8];
    int state = radio.receive(byteArr, 8);
  */
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("[SX1262] Received packet!"));
    Serial.print(F("[SX1262] Data:\t"));
    Serial.print(str);
    Serial.print("\t\tRSSI: ");
    Serial.println(rssi);
  } else if (state == RADIOLIB_ERR_RX_TIMEOUT) {
    Serial.println(F("[SX1262] Timed out while waiting for packet!"));
  } else {
    Serial.println(F("[SX1262] Failed to receive packet, code "));
    Serial.println(state);
  }

}

And the results!

Rx Gain on:

load:0x403cc700,len:0x2fd0
entry 0x403c98ac
[SX1262] Initializing ... success!
Rx Gain: 1
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
[SX1262] Received packet!
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............

Rx Gain off:

load:0x403cc700,len:0x2fd0
entry 0x403c98ac
[SX1262] Initializing ... success!
Rx Gain: 0
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
[SX1262] Received packet!
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -42.50
[SX1262] Received packet!
[SX1262] Data:	Hello World!		RSSI: -43.00
                    ...............

There is slight variation in the RSSI +-0.5, so I would say it is receiving. But no visible variation with Rx Gain on or off.

Weird!

0 replies

HeadBoffin · 2024-09-25T12:34:37Z

HeadBoffin
Sep 25, 2024
Collaborator

I hope you have lots of money to pay for the courts, fines and lawyers from breaching almost every air time law anywhere?

Whilst you are moving funds, perhaps wonder how it helps us to help you with such a long long log of repetition??

1 reply

Celliwig Sep 25, 2024
Author

I hope you have lots of money to pay for the courts, fines and lawyers from breaching almost every air time law anywhere?

If my reading of IR2030 is correct (might not be), there are no duty cycle restrictions on that band, below 5mW erp. The sx1276 with the output set to the lowest possible value, 2, should be below that...

Whilst you are moving funds, perhaps wonder how it helps us to help you with such a long long log of repetition??

Apart from showing that the RSSI does actually occasionally shift, not much I suppose. Edited for brevity.

jgromes · 2024-09-25T16:01:24Z

jgromes
Sep 25, 2024
Maintainer

I did some testing on my own, and I can confirm the behavior is not what I would expect. Enabling or disabling the boosted Rx gain doesn't seem to influence the actual values of the packet or instant RSSI (nor LoRa SNR for that matter) for FSK or LoRa modem. And I can also see the value in the register updating, as expected.

So TL;DR, I don't know. It is possible we are just using it incorrectly, maybe it has to be sent at a specific time (e.g. before something else is configured). The right people to ask would be the manufcaturer, i.e. Semtech. Unfoprutnately they took down their developer forum, so right now the only public communication channel is their git repositories.

1 reply

Celliwig Sep 25, 2024
Author

Okay, many thanks jgromes for confirming my observations, I appreciate that. Even if it doesn't work as expected, at least it's doing it for 'everybody'. Discounts the problem being a broken module at least!

I'll continue tweaking things to see if I can get it play ball, if I find anything I'll post back.

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SX1262: Does enabling setRxBoostedGainMode increase the RSSI value for FSK reception #1232

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