SX1280 on Pi Pico clone (Pimoroni Pico Lipo)

[DimitrisTS12]

Hi All, I am trying to get two SX1280 modules (RFSolutions Lambda80) to communicate with each other. I have tried vibecoding, and just copying code from the examples for the 1280 to little success. This is what I have at the moment:

For the TX:

#include <RadioLib.h>
SX1280 radio = new Module(17, 22, 20, 21);

int counter = 0;

void setup() {
  Serial.begin(9600);
  SPI.begin();
  // initialize SX1280 with default settings
  Serial.print(F("[SX1280] Initializing ... "));
  int state = radio.beginFLRC();
  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);
    while (true) { delay(10); }
  }

  // if needed, you can switch between any of the modems
  //
  // radio.begin()       start LoRa modem (and disable FLRC)
  //radio.beginFLRC()   //start FLRC modem (and disable LoRa)

  // the following settings can also
  // be modified at run-time
  state = radio.setFrequency(2410.5);
  state = radio.setBitRate(520);
  state = radio.setCodingRate(2);
  state = radio.setOutputPower(5);
  state = radio.setDataShaping(1.0);
  uint8_t syncWord[] = {0x01, 0x23, 0x45, 0x67};
  state = radio.setSyncWord(syncWord, 4);
  if (state != RADIOLIB_ERR_NONE) {
    Serial.print(F("Unable to set configuration, code "));
    Serial.println(state);
    while (true) { delay(10); }
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  String msg = String(counter);
  int state = radio.transmit(msg);

  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("[SX1280] Packet transmitted successfully!"));
  } else if (state == RADIOLIB_ERR_PACKET_TOO_LONG) {
    Serial.println(F("[SX1280] Packet too long!"));
  } else if (state == RADIOLIB_ERR_TX_TIMEOUT) {
    Serial.println(F("[SX1280] Timed out while transmitting!"));
  } else {
    Serial.println(F("[SX1280] Failed to transmit packet, code "));
    Serial.println(state);
  }

  counter++;

  delay(1000);
}

And my RX code is as follows:

#include <RadioLib.h>
#include <SPI.h>

// NSS, DIO1, RESET, BUSY
SX1280 radio = new Module(17, 22, 20, 21);

void setup() {

  Serial.begin(9600);

  // Configure Pico SPI pins
  SPI.setRX(16);
  SPI.setTX(19);
  SPI.setSCK(18);
  SPI.begin();

  Serial.print(F("[SX1280] Initializing ... "));

  int state = radio.beginFLRC();

  if (state == RADIOLIB_ERR_NONE) {
    Serial.println(F("success!"));
  } else {
    Serial.print(F("failed, code "));
    Serial.println(state);

    while (true) {
      delay(10);
    }
  }

  // Radio configuration
  radio.setFrequency(2410.5);
  radio.setBitRate(520);
  radio.setCodingRate(2);
  radio.setOutputPower(5);
  radio.setDataShaping(1.0);

  uint8_t syncWord[] = {0x01, 0x23, 0x45, 0x67};
  radio.setSyncWord(syncWord, 4);

  Serial.println(F("Receiver ready"));
}

void loop() {

  String str;

  int state = radio.receive(str);

  if (state == RADIOLIB_ERR_NONE) {

    Serial.println(F("[SX1280] Received packet!"));

    Serial.print(F("[SX1280] Data: "));
    Serial.println(str);

    Serial.print(F("[SX1280] RSSI: "));
    Serial.println(radio.getRSSI());

  } else if (state == RADIOLIB_ERR_RX_TIMEOUT) {

    Serial.println(F("[SX1280] RX timeout"));

  } else {

    Serial.print(F("[SX1280] Failed, code "));
    Serial.println(state);
  }
}`

The wiring on both breadboards is the same.

SCLK GP18
SDI GP19
SDO GP16
nSel GP17
RESET GP20
DIO1 GP21
BUSY GP22

The output on the serial monitor of the TX is always "packet sent succesfully" but on the RX the serial monitor shows zero rssi and nothing for the string, but also no errors.

[K4KDR]

It's a huge help if you have an SDR that you can set to the freq. being used to see what, if anything, is actually being transmitted over-the-air. I've caught a lot of mistakes that way.

[DimitrisTS12]

Are there budget options for this? HackRF are so expensive

[K4KDR]

You might want to search for down-converters. That puts the signal down in the range of any SDR.

[jgromes]

I would recommend to start simpler - first, try to get the LoRa modem working since it is the one that is most tolerant to bad configuration, frequency offsets, noise, low power etc.

You should also use interrupt-driven receive mode, as the blocking receive which you are using now is very likely to miss packets between the calls to receive.

[DimitrisTS12]

Thanks for this. If I set the pins correctly can I use the given code? And which would be a better Transmit mode?

[jgromes]

Yes, all the examples are set up in a way that usually changing the pins/SPI is the only thing that's needed to make them work. For transmit mode blocking is fine unless you are transmitting very long packets, or have some timing constraints (like needing to e.g. handle some periodic actions every N milliseconds in your code).