nrf52840 RADIO_MODE_MODE_Ble_LR125Kbit

Question

// CRC Config
    NRF_RADIO->CRCCNF = (RADIO_CRCCNF_LEN_Three << RADIO_CRCCNF_LEN_Pos); // Number of checksum bits
    if ((NRF_RADIO->CRCCNF & RADIO_CRCCNF_LEN_Msk) == (RADIO_CRCCNF_LEN_Two << RADIO_CRCCNF_LEN_Pos))
    {
        NRF_RADIO->CRCINIT = 0xFFFFUL;   // Initial value
        NRF_RADIO->CRCPOLY = 0x11021UL;  // CRC poly: x^16 + x^12^x^5 + 1
    }
    else if ((NRF_RADIO->CRCCNF & RADIO_CRCCNF_LEN_Msk) == (RADIO_CRCCNF_LEN_One << RADIO_CRCCNF_LEN_Pos))
    {
        NRF_RADIO->CRCINIT = 0xFFUL;   // Initial value
        NRF_RADIO->CRCPOLY = 0x107UL;  // CRC poly: x^8 + x^2^x^1 + 1
    }
    else if ((NRF_RADIO->CRCCNF & RADIO_CRCCNF_LEN_Msk) == (RADIO_CRCCNF_LEN_Three << RADIO_CRCCNF_LEN_Pos))
    {
        NRF_RADIO->CRCINIT = 0xFFFFFFUL;   // Initial value
        NRF_RADIO->CRCPOLY = 0x107UL;  // CRC poly: x^8 + x^2^x^1 + 1
    }

How should the CRCINIT and CRCPOLY be set?

Thanks

Dmitry · Accepted Answer

Hi,

CRC parameters are the same for 1M and LR125. For BLE advertising channel, here is the right setup of CRC:

NRF_RADIO->CRCCNF  = (RADIO_CRCCNF_LEN_Three << RADIO_CRCCNF_LEN_Pos) | 
                       (RADIO_CRCCNF_SKIPADDR_Skip << RADIO_CRCCNF_SKIPADDR_Pos); // Skip Address when computing crc     
  NRF_RADIO->CRCINIT = 0x555555;    // Initial value of CRC
  NRF_RADIO->CRCPOLY = 0x00065B;    // CRC polynomial function

For data channel, CRCINIT is passed in CONNECT_IND message. If you are implementing some custom protocol, you're on your own.

nrf52840 RADIO_MODE_MODE_Ble_LR125Kbit

Top Replies