Check if (and which) SPI devices is connected (NRF24L01 and SX1278 LoRa modules)



  • Hi,

    I Have a small arduino atmega 328p based sensor board.
    I want too be able to choose which wireless board (NRF24L01 or SX1278) I hard connect to it without reprogramming it, it may be fast and useful for my distance tests.

    I actually use those libraries separately with success :

    The problem is that if I use one library with the matching chip disconnected, when I will initialise it, my atmega will freeze (get stuck and do nothing).
    So I wonder how to check if a SPI module is physically connected and how recognize which one it is so I could initialise the corresponding library or simply go to deep sleep.

    How could I easily do this SPI check?

    Thanks for reading, sorry for my poor English level 😕



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  • Well.. The quick answer I guess would be Yes, it is possible. But I imagine you would need to know a little bit about how the different components work. I also use the LoRa library from Sandeep Mistry and if you take a look at the code that initializes the card you find the following:

      // check version
      uint8_t version = readRegister(REG_VERSION);
      if (version != 0x12) {
        return 0;
      }
    

    Which is using the function readRegister:

    uint8_t LoRaClass::readRegister(uint8_t address)
    {
      return singleTransfer(address & 0x7f, 0x00);
    }
    

    Which is using the function singleTransfer:

    uint8_t LoRaClass::singleTransfer(uint8_t address, uint8_t value)
    {
      uint8_t response;
    
      digitalWrite(_ss, LOW);
    
      _spi->beginTransaction(_spiSettings);
      _spi->transfer(address);
      response = _spi->transfer(value);
      _spi->endTransaction();
    
      digitalWrite(_ss, HIGH);
    
      return response;
    }
    

    Which is using pretty simple SPI commands. So perhaps you could do the same and select the LoRa library if the version is 0x12 or else select the nRF library.

    I don't know if there is enough space on the 328p to load both the libraries? And if you want to use the mysensors library it would be more complicated i suppose..


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