RE: Using NRF52840 RADIO with basic/custom protocol without ESB

ejbasile — Tue, 23 Nov 2021 11:49:02 GMT

Hi Håkon,

I added the following function to both sides before initiatialization:

/**
 * Start the High Frequency Clock
 */
inline void start_hf_clock()
{
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);
  NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
}

And I verified that the HFCLKSTAT register was at 0x10001 following the execution of that function (triggered before the enabling for transmission and reception commands below).

// TRANSMITTER BOARD
NRF_RADIO->TASKS_TXEN = 1UL; // Enable the RADIO in TX Mode

// RECEIVER BOARD
NRF_RADIO->TASKS_RXEN = 1UL; // Enable the RADIO in RX Mode

Still, the issue seems to persist. I will provide a breakdown of each of my initialization functions.

Transmitter Functions:

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   POSITIONS & MASKS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

enum NRF_RADIO_PCNF0_POS
{
  RADIO_PCNF0_LFLEN_POS   = 0UL,
  RADIO_PCNF0_S0LEN_POS   = 8UL,
  RADIO_PCNF0_S1LEN_POS   = 16UL,
  RADIO_PCNF0_S1INCL_POS  = 20UL,
  RADIO_PCNF0_CILEN_POS   = 22UL,
  RADIO_PCNF0_PLEN_POS    = 24UL,
  RADIO_PCNF0_CRCINC_POS  = 26UL,
  RADIO_PCNF0_TERMLEN_POS = 29UL
};

enum NRF_RADIO_PCNF0_MSK
{
  RADIO_PCNF0_LFLEN_MSK   = 0x000FUL,
  RADIO_PCNF0_S0LEN_MSK   = 0x0001UL,
  RADIO_PCNF0_S1LEN_MSK   = 0x000FUL,
  RADIO_PCNF0_S1INCL_MSK  = 0x0001UL,
  RADIO_PCNF0_CILEN_MSK   = 0x0003UL,
  RADIO_PCNF0_PLEN_MSK    = 0x0003UL,
  RADIO_PCNF0_CRCINC_MSK  = 0x0001UL,
  RADIO_PCNF0_TERMLEN_MSK = 0x0003UL
};

enum NRF_RADIO_PCNF1_POS
{
  RADIO_PCNF1_MAXLEN_POS  = 0UL,
  RADIO_PCNF1_STATLEN_POS = 8UL,
  RADIO_PCNF1_BALEN_POS   = 16UL,
  RADIO_PCNF1_ENDIAN_POS  = 24UL,
  RADIO_PCNF1_WHITEEN_POS = 25UL
};

enum NRF_RADIO_PCNF1_MSK
{
  RADIO_PCNF1_MAXLEN_MSK  = 0x00FFUL,
  RADIO_PCNF1_STATLEN_MSK = 0x00FFUL,
  RADIO_PCNF1_BALEN_MSK   = 0x0007UL,
  RADIO_PCNF1_ENDIAN_MSK  = 0x0001UL,
  RADIO_PCNF1_WHITEEN_MSK = 0x0001UL
};

enum NRF_RADIO_PREFIX0_POS
{
  RADIO_PREFIX0_AP0 = 0UL,
  RADIO_PREFIX0_AP1 = 8UL,
  RADIO_PREFIX0_AP2 = 16UL,
  RADIO_PREFIX0_AP3 = 24UL
};

enum NRF_PREFIX1_POS
{
  RADIO_PREFIX1_AP4 = 0UL,
  RADIO_PREFIX1_AP5 = 8UL,
  RADIO_PREFIX1_AP6 = 16UL,
  RADIO_PREFIX1_AP7 = 24UL
};

enum NRF_RADIO_PREFIX_MSK
{
  RADIO_PREFIX_MSK = 0xFFUL
};

enum NRF_RADIO_TXADDRESS_MSK
{
  RADIO_TXADDRESS_MSK = 0x0007UL
};

enum NRF_RADIO_CRCCNF_POS
{
  RADIO_CRCCNF_LEN_POS      = 0UL,
  RADIO_CRCCNF_SKIPADDR_POS = 8UL
};

enum NRF_RADIO_CRCCNF_MSK
{
  RADIO_CRCCNF_LEN_MSK = 0x0003UL,
  RADIO_CRCCNF_SKIPADDR_MSK = 0x0003UL
};

enum NRF_RADIO_CRCPOLY_MSK
{
  RADIO_CRCPOLY_MSK = 0xFFFFFFUL
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   VALUE IDS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////


// Data Rate and Modulation
enum NRF_RADIO_MODE
{
  NRF_1MBIT          = 0,  // 1 Mbit/s Nordic proprietary radio mode
  NRF_2MBIT          = 1,  // 2 Mbit/s Nordic proprietary radio mode
  BLE_1MBIT          = 3,  // 1 Mbit/s BLE
  BLE_2MBIT          = 4,  // 2 Mbit/s BLE
  BLE_LR125KBIT      = 5,  // Long range 125 kbit/s TX, 125 kbit/s and 500 kbit/s RX
  BLE_LR500KBIT      = 6,  // Long range 500 kbit/s TX, 125 kbit/s and 500 kbit/s RX
  IEEE802154_250KBIT = 15  // IEEE 802.15.4-2006 250 kbit/s
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   HELPER FUNCTIONS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * Set PCNF0 Register in NRF RADIO Peripheral
 * 
 * @param length_field_len: Length on air of LENGTH field in number of bits.
 * @param s0_field_len: Length on air of S0 field in number of bytes.
 * @param s1_field_len: Length on air of S1 field in number of bits.
 * @param include_s1_field: Include or exclude S1 field in RAM
 * @param code_indicator_len: Length of code indicator - long range
 * @param preamble_len: Length of preamble on air. Decision point: TASKS_START task
 * @param include_crc_in_len: Indicates if LENGTH field contains CRC or not
 * @param term_field_len: Length of TERM field in Long Range operation
 */
void set_pcnf0(uint32_t length_field_len, 
               uint32_t s0_field_len,
               uint32_t s1_field_len,
               uint32_t include_s1_field,
               uint32_t code_indicator_len,
               uint32_t preamble_len,
               uint32_t include_crc,
               uint32_t term_field_len)
{
  assert(length_field_len   <= RADIO_PCNF0_LFLEN_MSK);
  assert(s0_field_len       <= RADIO_PCNF0_S0LEN_MSK);
  assert(s1_field_len       <= RADIO_PCNF0_S1LEN_MSK);
  assert(include_s1_field   <= RADIO_PCNF0_S1INCL_MSK);
  assert(code_indicator_len <= RADIO_PCNF0_CILEN_MSK);
  assert(preamble_len       <= RADIO_PCNF0_PLEN_MSK);
  assert(include_crc        <= RADIO_PCNF0_CRCINC_MSK);
  assert(term_field_len     <= RADIO_PCNF0_TERMLEN_MSK);
  
  NRF_RADIO->PCNF0 = (length_field_len   << RADIO_PCNF0_LFLEN_POS)  |
                     (s0_field_len       << RADIO_PCNF0_S0LEN_POS)  |
                     (s1_field_len       << RADIO_PCNF0_S1LEN_POS)  |
                     (include_s1_field   << RADIO_PCNF0_S1INCL_POS) |
                     (code_indicator_len << RADIO_PCNF0_CILEN_POS)  |
                     (preamble_len       << RADIO_PCNF0_PLEN_POS)   |
                     (include_crc        << RADIO_PCNF0_CRCINC_POS) |
                     (term_field_len     << RADIO_PCNF0_TERMLEN_POS);
}

/**
 * Set PCNF1 Register in NRF RADIO Peripheral
 * 
 * @param maximum_packet_payload_length: Maximum length of packet payload
 * @param static_length: Static length in number of bytes
 * @param base_address_length: Base address length in number of bytes
 * @param endianness: On air endianness of packet, this applies to the S0, LENGTH, S1 and the PAYLOAD fields.
 * @param packet_whitening_enable: Enable or disable packet whitening
 */
void set_pcnf1(uint32_t maximum_packet_payload_length,
               uint32_t static_length,
               uint32_t base_address_length,
               uint32_t endianness,
               uint32_t packet_whitening_enable)
{
  assert(maximum_packet_payload_length <= RADIO_PCNF1_MAXLEN_MSK);
  assert(static_length                 <= RADIO_PCNF1_STATLEN_MSK);
  assert(base_address_length           <= RADIO_PCNF1_BALEN_MSK);
  assert(endianness                    <= RADIO_PCNF1_ENDIAN_MSK);
  assert(packet_whitening_enable       <= RADIO_PCNF1_WHITEEN_MSK);

  NRF_RADIO->PCNF1 = (maximum_packet_payload_length << RADIO_PCNF1_MAXLEN_POS)  |
                     (static_length                 << RADIO_PCNF1_STATLEN_POS) |
                     (base_address_length           << RADIO_PCNF1_BALEN_POS)   |
                     (endianness                    << RADIO_PCNF1_ENDIAN_POS)  |
                     (packet_whitening_enable       << RADIO_PCNF1_WHITEEN_POS);
}

/**
 * Set the BASE Register
 * 
 * @param base_address: Base address 0
 */
void set_base0(uint32_t base_address)
{
  NRF_RADIO->BASE0 = base_address;
}

/**
 * Set the PREFIX0.AP0 Register
 * 
 * @param prefix0_address: PREFIX0 Address for AP0
 */
void set_prefix0_ap0(uint32_t prefix0_address)
{
  prefix0_address &= RADIO_PREFIX_MSK;
  NRF_RADIO->PREFIX0 = prefix0_address << RADIO_PREFIX0_AP0;
}

/**
 * Set the transmission address
 * 
 * @param tx_address: Transmission Address
 */
void set_txaddress(uint32_t tx_address)
{
  tx_address &= RADIO_TXADDRESS_MSK;
  NRF_RADIO->TXADDRESS = tx_address;
}

/**
 * Configure the CRC
 * 
 * @param crc_length: CRC length in number of bytes.
 * @param crc_skipaddress: Include or exclude packet address field out of CRC calculation.
 */
void configure_crc(uint32_t crc_length, uint32_t crc_skipaddress)
{
  assert(crc_length      <= RADIO_CRCCNF_LEN_MSK);
  assert(crc_skipaddress <= RADIO_CRCCNF_SKIPADDR_MSK);
  
  NRF_RADIO->CRCCNF = (crc_length      << RADIO_CRCCNF_LEN_POS) |
                      (crc_skipaddress << RADIO_CRCCNF_SKIPADDR_MSK);
}

/**
 * Set the CRC Polynomial
 * 
 * @param crc_polynomial: CRC Polynomial
 *                        Each term in the CRC polynomial is mapped to a bit in this register which index 
 *                        corresponds to the term's exponent. The least significant term/bit is hard-wired 
 *                        internally to 1, and bit number 0 of the register content is ignored by the hardware. 
 *                        The following example is for an 8 bit CRC polynomial: x8 + x7 + x3 + x2 + 1 = 1 1000 1101 .
 */
void set_crc_polynomial(uint32_t crc_polynomial)
{
  crc_polynomial &= RADIO_CRCPOLY_MSK;
  NRF_RADIO->CRCPOLY = crc_polynomial;
}

/**
 * Prepare the NRF RADIO Peripheral Packet Pointer (Double Buffered)
 */
inline void prepare_radio_packet_ptr(uint8_t* packet_ptr)
{
  NRF_RADIO->PACKETPTR = (uint32_t)packet_ptr;
}

/**
 * Set the radio frequency
 * 
 * @param frequency: X + 2400MHz
 */
inline void set_radio_frequency(uint32_t frequency)
{
  assert(frequency <= 100);

  NRF_RADIO->FREQUENCY = frequency;
}

/**
 * Transmit a Packet using the NRF RADIO Peripheral
 */
inline void tx_radio_packet()
{
  NRF_RADIO->TASKS_START = 1UL;
  while(NRF_RADIO->EVENTS_END == 0); // Wait for the packet to finish transmission
}

/**
 * Start the High Frequency Clock
 */
inline void start_hf_clock()
{
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);
  NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   APPLICATION-SPECIFIC FUNCTIONS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * Initialize the NRF RADIO Peripheral in the desired configuration for Transmission to the Relay
 */
void init_radio_for_transmission()
{ 
  NRF_RADIO->MODE = NRF_2MBIT; // Set to 2Mbps bandwidth

  // Set the PCNF0 & PCNF1 registers
  set_pcnf0(8UL, 0UL, 0UL, 0UL, 0UL, 2UL, 0UL, 0UL);
  set_pcnf1(255UL, 0UL, 4UL, 0UL, 1UL);

  // Set the BASE and PREFIX registers
  set_base0(0xABCDDBF5);
  set_prefix0_ap0(0xEF);
  set_txaddress(0x00); // Logical Address 0
  set_radio_frequency(0x00); // Set to 2400MHz

  // Set the CRCCNF & CRCPOLY Registers
  configure_crc(2UL, 0UL);

  // Set the CRC Polynomial - Utilizing this table:
  //   https://users.ece.cmu.edu/~koopman/crc/
  //    - From Carnegie Mellon University
  set_crc_polynomial(0xd175);

  start_hf_clock();
  
  NRF_RADIO->TASKS_TXEN = 1UL; // Enable the Transmitter
}

Receiver Functions:

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   POSITIONS & MASKS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

enum NRF_RADIO_PCNF0_POS
{
  RADIO_PCNF0_LFLEN_POS   = 0UL,
  RADIO_PCNF0_S0LEN_POS   = 8UL,
  RADIO_PCNF0_S1LEN_POS   = 16UL,
  RADIO_PCNF0_S1INCL_POS  = 20UL,
  RADIO_PCNF0_CILEN_POS   = 22UL,
  RADIO_PCNF0_PLEN_POS    = 24UL,
  RADIO_PCNF0_CRCINC_POS  = 26UL,
  RADIO_PCNF0_TERMLEN_POS = 29UL
};

enum NRF_RADIO_PCNF0_MSK
{
  RADIO_PCNF0_LFLEN_MSK   = 0x000FUL,
  RADIO_PCNF0_S0LEN_MSK   = 0x0001UL,
  RADIO_PCNF0_S1LEN_MSK   = 0x000FUL,
  RADIO_PCNF0_S1INCL_MSK  = 0x0001UL,
  RADIO_PCNF0_CILEN_MSK   = 0x0003UL,
  RADIO_PCNF0_PLEN_MSK    = 0x0003UL,
  RADIO_PCNF0_CRCINC_MSK  = 0x0001UL,
  RADIO_PCNF0_TERMLEN_MSK = 0x0003UL
};

enum NRF_RADIO_PCNF1_POS
{
  RADIO_PCNF1_MAXLEN_POS  = 0UL,
  RADIO_PCNF1_STATLEN_POS = 8UL,
  RADIO_PCNF1_BALEN_POS   = 16UL,
  RADIO_PCNF1_ENDIAN_POS  = 24UL,
  RADIO_PCNF1_WHITEEN_POS = 25UL
};

enum NRF_RADIO_PCNF1_MSK
{
  RADIO_PCNF1_MAXLEN_MSK  = 0x00FFUL,
  RADIO_PCNF1_STATLEN_MSK = 0x00FFUL,
  RADIO_PCNF1_BALEN_MSK   = 0x0007UL,
  RADIO_PCNF1_ENDIAN_MSK  = 0x0001UL,
  RADIO_PCNF1_WHITEEN_MSK = 0x0001UL
};

enum NRF_RADIO_PREFIX0_POS
{
  RADIO_PREFIX0_AP0 = 0UL,
  RADIO_PREFIX0_AP1 = 8UL,
  RADIO_PREFIX0_AP2 = 16UL,
  RADIO_PREFIX0_AP3 = 24UL
};

enum NRF_PREFIX1_POS
{
  RADIO_PREFIX1_AP4 = 0UL,
  RADIO_PREFIX1_AP5 = 8UL,
  RADIO_PREFIX1_AP6 = 16UL,
  RADIO_PREFIX1_AP7 = 24UL
};

enum NRF_RADIO_PREFIX_MSK
{
  RADIO_PREFIX_MSK = 0xFFUL
};

enum NRF_RADIO_TXADDRESS_MSK
{
  RADIO_TXADDRESS_MSK = 0x0007UL
};

typedef enum NRF_RADIO_RXADDRESS_POS
{
  RADIO_RX_ADDRESS0_POS = 0UL,
  RADIO_RX_ADDRESS1_POS = 1UL,
  RADIO_RX_ADDRESS2_POS = 2UL,
  RADIO_RX_ADDRESS3_POS = 3UL,
  RADIO_RX_ADDRESS4_POS = 4UL,
  RADIO_RX_ADDRESS5_POS = 5UL,
  RADIO_RX_ADDRESS6_POS = 6UL,
  RADIO_RX_ADDRESS7_POS = 7UL
} nrf_radio_rxaddress_pos_t;

enum NRF_RADIO_CRCCNF_POS
{
  RADIO_CRCCNF_LEN_POS      = 0UL,
  RADIO_CRCCNF_SKIPADDR_POS = 8UL
};

enum NRF_RADIO_CRCCNF_MSK
{
  RADIO_CRCCNF_LEN_MSK = 0x0003UL,
  RADIO_CRCCNF_SKIPADDR_MSK = 0x0003UL
};

enum NRF_RADIO_CRCPOLY_MSK
{
  RADIO_CRCPOLY_MSK = 0xFFFFFFUL
};

typedef enum NRF_RADIO_SHORTS_POS
{
  RADIO_SHORTS_READY_START_POS        = 0UL,
  RADIO_SHORTS_END_DISABLE_POS        = 1UL,
  RADIO_SHORTS_DISABLED_TXEN_POS      = 2UL,
  RADIO_SHORTS_DISABLED_RXEN_POS      = 3UL,
  RADIO_SHORTS_ADDRESS_RSSISTART_POS  = 4UL,
  RADIO_SHORTS_END_START_POS          = 5UL,
  RADIO_SHORTS_ADDRESS_BCSTART_POS    = 6UL,
  RADIO_SHORTS_DISABLED_RSSISTOP_POS  = 8UL,
  RADIO_SHORTS_RXREADY_CCASTART_POS   = 11UL,
  RADIO_SHORTS_CCAIDLE_TXEN_POS       = 12UL,
  RADIO_SHORTS_CCABUSY_DISABLE_POS    = 13UL,
  RADIO_SHORTS_FRAMESTART_BCSTART_POS = 14UL,
  RADIO_SHORTS_READY_EDSTART_POS      = 15UL,
  RADIO_SHORTS_EDEND_DISABLE_POS      = 16UL,
  RADIO_SHORTS_CCAIDLE_STOP_POS       = 17UL,
  RADIO_SHORTS_TXREADY_START_POS      = 18UL,
  RADIO_SHORTS_RXREADY_START_POS      = 19UL,
  RADIO_SHORTS_PHYEND_DISABLE_POS     = 20UL,
  RADIO_SHORTS_PHYEND_START_POS       = 21UL
} nrf_radio_shorts_pos_t;


typedef enum NRF_RADIO_SHORTS_MSK
{
  RADIO_SHORTS_READY_START_MSK        = 0x000001UL,
  RADIO_SHORTS_END_DISABLE_MSK        = 0x000002UL,
  RADIO_SHORTS_DISABLED_TXEN_MSK      = 0x000004UL,
  RADIO_SHORTS_DISABLED_RXEN_MSK      = 0x000008UL,
  RADIO_SHORTS_ADDRESS_RSSISTART_MSK  = 0x000010UL,
  RADIO_SHORTS_END_START_MSK          = 0x000020UL,
  RADIO_SHORTS_ADDRESS_BCSTART_MSK    = 0x000040UL,
  RADIO_SHORTS_DISABLED_RSSISTOP_MSK  = 0x000100UL,
  RADIO_SHORTS_RXREADY_CCASTART_MSK   = 0x000800UL,
  RADIO_SHORTS_CCAIDLE_TXEN_MSK       = 0x001000UL,
  RADIO_SHORTS_CCABUSY_DISABLE_MSK    = 0x002000UL,
  RADIO_SHORTS_FRAMESTART_BCSTART_MSK = 0x004000UL,
  RADIO_SHORTS_READY_EDSTART_MSK      = 0x008000UL,
  RADIO_SHORTS_EDEND_DISABLE_MSK      = 0x010000UL,
  RADIO_SHORTS_CCAIDLE_STOP_MSK       = 0x020000UL,
  RADIO_SHORTS_TXREADY_START_MSK      = 0x040000UL,
  RADIO_SHORTS_RXREADY_START_MSK      = 0x080000UL,
  RADIO_SHORTS_PHYEND_DISABLE_MSK     = 0x100000UL,
  RADIO_SHORTS_PHYEND_START_MSK       = 0x200000UL
} nrf_radio_shorts_msk_t;

typedef enum NRF_RADIO_INTENSET_POS
{
  RADIO_INTENSET_READY_POS      = 0UL,
  RADIO_INTENSET_ADDRESS_POS    = 1UL,
  RADIO_INTENSET_PAYLOAD_POS    = 2UL,
  RADIO_INTENSET_END_POS        = 3UL,
  RADIO_INTENSET_DISABLED_POS   = 4UL,
  RADIO_INTENSET_DEVMATCH_POS   = 5UL,
  RADIO_INTENSET_DEVMISS_POS    = 6UL,
  RADIO_INTENSET_RSSIEND_POS    = 7UL,
  RADIO_INTENSET_BCMATCH_POS    = 10UL,
  RADIO_INTENSET_CRCOK_POS      = 12UL,
  RADIO_INTENSET_CRCERROR_POS   = 13UL,
  RADIO_INTENSET_FRAMESTART_POS = 14UL,
  RADIO_INTENSET_EDEND_POS      = 15UL,
  RADIO_INTENSET_EDSTOPPED_POS  = 16UL,
  RADIO_INTENSET_CCAIDLE_POS    = 17UL,
  RADIO_INTENSET_CCABUSY_POS    = 18UL,
  RADIO_INTENSET_CCASTOPPED_POS = 19UL,
  RADIO_INTENSET_RATEBOOST_POS  = 20UL,
  RADIO_INTENSET_TXREADY_POS    = 21UL,
  RADIO_INTENSET_RXREADY_POS    = 22UL,
  RADIO_INTENSET_MHRMATCH_POS   = 23UL,
  RADIO_INTENSET_SYNC_POS       = 26UL,
  RADIO_INTENSET_PHYEND_POS     = 27UL
} nrf_radio_intenset_pos_t;

typedef enum NRF_RADIO_INTENSET_MSK
{
  RADIO_INTENSET_READY_MSK      = 0x0000001UL,
  RADIO_INTENSET_ADDRESS_MSK    = 0x0000002UL,
  RADIO_INTENSET_PAYLOAD_MSK    = 0x0000004UL,
  RADIO_INTENSET_END_MSK        = 0x0000008UL,
  RADIO_INTENSET_DISABLED_MSK   = 0x0000010UL,
  RADIO_INTENSET_DEVMATCH_MSK   = 0x0000020UL,
  RADIO_INTENSET_DEVMISS_MSK    = 0x0000040UL,
  RADIO_INTENSET_RSSIEND_MSK    = 0x0000080UL,
  RADIO_INTENSET_BCMATCH_MSK    = 0x0000400UL,
  RADIO_INTENSET_CRCOK_MSK      = 0x0001000UL,
  RADIO_INTENSET_CRCERROR_MSK   = 0x0002000UL,
  RADIO_INTENSET_FRAMESTART_MSK = 0x0004000UL,
  RADIO_INTENSET_EDEND_MSK      = 0x0008000UL,
  RADIO_INTENSET_EDSTOPPED_MSK  = 0x0010000UL,
  RADIO_INTENSET_CCAIDLE_MSK    = 0x0020000UL,
  RADIO_INTENSET_CCABUSY_MSK    = 0x0040000UL,
  RADIO_INTENSET_CCASTOPPED_MSK = 0x0080000UL,
  RADIO_INTENSET_RATEBOOST_MSK  = 0x0100000UL,
  RADIO_INTENSET_TXREADY_MSK    = 0x0200000UL,
  RADIO_INTENSET_RXREADY_MSK    = 0x0400000UL,
  RADIO_INTENSET_MHRMATCH_MSK   = 0x0800000UL,
  RADIO_INTENSET_SYNC_MSK       = 0x4000000UL,
  RADIO_INTENSET_PHYEND_MSK     = 0x8000000UL
} nrf_radio_intenset_msk_t;

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   VALUE IDS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////


// Data Rate and Modulation
enum NRF_RADIO_MODE
{
  NRF_1MBIT          = 0,  // 1 Mbit/s Nordic proprietary radio mode
  NRF_2MBIT          = 1,  // 2 Mbit/s Nordic proprietary radio mode
  BLE_1MBIT          = 3,  // 1 Mbit/s BLE
  BLE_2MBIT          = 4,  // 2 Mbit/s BLE
  BLE_LR125KBIT      = 5,  // Long range 125 kbit/s TX, 125 kbit/s and 500 kbit/s RX
  BLE_LR500KBIT      = 6,  // Long range 500 kbit/s TX, 125 kbit/s and 500 kbit/s RX
  IEEE802154_250KBIT = 15  // IEEE 802.15.4-2006 250 kbit/s
};

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   HELPER FUNCTIONS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * Set PCNF0 Register in NRF RADIO Peripheral
 * 
 * @param length_field_len: Length on air of LENGTH field in number of bits.
 * @param s0_field_len: Length on air of S0 field in number of bytes.
 * @param s1_field_len: Length on air of S1 field in number of bits.
 * @param include_s1_field: Include or exclude S1 field in RAM
 * @param code_indicator_len: Length of code indicator - long range
 * @param preamble_len: Length of preamble on air. Decision point: TASKS_START task
 * @param include_crc_in_len: Indicates if LENGTH field contains CRC or not
 * @param term_field_len: Length of TERM field in Long Range operation
 */
void set_pcnf0(uint32_t length_field_len, 
               uint32_t s0_field_len,
               uint32_t s1_field_len,
               uint32_t include_s1_field,
               uint32_t code_indicator_len,
               uint32_t preamble_len,
               uint32_t include_crc,
               uint32_t term_field_len)
{
  length_field_len   &= RADIO_PCNF0_LFLEN_MSK;
  s0_field_len       &= RADIO_PCNF0_S0LEN_MSK;
  s1_field_len       &= RADIO_PCNF0_S1LEN_MSK;
  include_s1_field   &= RADIO_PCNF0_S1INCL_MSK;
  code_indicator_len &= RADIO_PCNF0_CILEN_MSK;
  preamble_len       &= RADIO_PCNF0_PLEN_MSK;
  include_crc        &= RADIO_PCNF0_CRCINC_MSK;
  term_field_len     &= RADIO_PCNF0_TERMLEN_MSK;
  
  NRF_RADIO->PCNF0 = (length_field_len   << RADIO_PCNF0_LFLEN_POS)  |
                     (s0_field_len       << RADIO_PCNF0_S0LEN_POS)  |
                     (s1_field_len       << RADIO_PCNF0_S1LEN_POS)  |
                     (include_s1_field   << RADIO_PCNF0_S1INCL_POS) |
                     (code_indicator_len << RADIO_PCNF0_CILEN_POS)  |
                     (preamble_len       << RADIO_PCNF0_PLEN_POS)   |
                     (include_crc        << RADIO_PCNF0_CRCINC_POS) |
                     (term_field_len     << RADIO_PCNF0_TERMLEN_POS);
}

/**
 * Set PCNF1 Register in NRF RADIO Peripheral
 * 
 * @param maximum_packet_payload_length: Maximum length of packet payload
 * @param static_length: Static length in number of bytes
 * @param base_address_length: Base address length in number of bytes
 * @param endianness: On air endianness of packet, this applies to the S0, LENGTH, S1 and the PAYLOAD fields.
 * @param packet_whitening_enable: Enable or disable packet whitening
 */
void set_pcnf1(uint32_t maximum_packet_payload_length,
               uint32_t static_length,
               uint32_t base_address_length,
               uint32_t endianness,
               uint32_t packet_whitening_enable)
{
  maximum_packet_payload_length &= RADIO_PCNF1_MAXLEN_MSK;
  static_length                 &= RADIO_PCNF1_STATLEN_MSK;
  base_address_length           &= RADIO_PCNF1_BALEN_MSK;
  endianness                    &= RADIO_PCNF1_ENDIAN_MSK;
  packet_whitening_enable       &= RADIO_PCNF1_WHITEEN_MSK;

  NRF_RADIO->PCNF1 = (maximum_packet_payload_length << RADIO_PCNF1_MAXLEN_POS)  |
                     (static_length                 << RADIO_PCNF1_STATLEN_POS) |
                     (base_address_length           << RADIO_PCNF1_BALEN_POS)   |
                     (endianness                    << RADIO_PCNF1_ENDIAN_POS)  |
                     (packet_whitening_enable       << RADIO_PCNF1_WHITEEN_POS);
}

/**
 * Set the BASE Register
 * 
 * @param base_address: Base address 0
 */
void set_base0(uint32_t base_address)
{
  NRF_RADIO->BASE0 = base_address;
}

/**
 * Set the PREFIX0.AP0 Register
 * 
 * @param prefix0_address: PREFIX0 Address for AP0
 */
void set_prefix0_ap0(uint32_t prefix0_address)
{
  prefix0_address &= RADIO_PREFIX_MSK;
  NRF_RADIO->PREFIX0 = prefix0_address << RADIO_PREFIX0_AP0;
}

/**
 * Set the transmission address
 * 
 * @param tx_address: Transmission Address
 */
void set_txaddress(uint32_t tx_address)
{
  tx_address &= RADIO_TXADDRESS_MSK;
  NRF_RADIO->TXADDRESS = tx_address;
}

/**
 * Enable the reception Address
 * 
 * @param rx_address_pos: RX Address Position in the register
 */
void enable_rxaddress(nrf_radio_rxaddress_pos_t rx_address_pos)
{
  NRF_RADIO->RXADDRESSES = 1UL << rx_address_pos;
}

/**
 * Disable the reception Address
 * 
 * @param rx_address_pos: RX Address Position in the register
 */
void disable_rxaddress(nrf_radio_rxaddress_pos_t rx_address_pos)
{
  NRF_RADIO->RXADDRESSES = 0UL << rx_address_pos;
}


/**
 * Configure the CRC
 * 
 * @param crc_length: CRC length in number of bytes.
 * @param crc_skipaddress: Include or exclude packet address field out of CRC calculation.
 */
void configure_crc(uint32_t crc_length, uint32_t crc_skipaddress)
{
  crc_length      &= RADIO_CRCCNF_LEN_MSK;
  crc_skipaddress &= RADIO_CRCCNF_SKIPADDR_MSK;
  
  NRF_RADIO->CRCCNF = (crc_length      << RADIO_CRCCNF_LEN_POS) |
                      (crc_skipaddress << RADIO_CRCCNF_SKIPADDR_MSK);
}

/**
 * Set the CRC Polynomial
 * 
 * @param crc_polynomial: CRC Polynomial
 *                        Each term in the CRC polynomial is mapped to a bit in this register which index 
 *                        corresponds to the term's exponent. The least significant term/bit is hard-wired 
 *                        internally to 1, and bit number 0 of the register content is ignored by the hardware. 
 *                        The following example is for an 8 bit CRC polynomial: x8 + x7 + x3 + x2 + 1 = 1 1000 1101 .
 */
void set_crc_polynomial(uint32_t crc_polynomial)
{
  crc_polynomial &= RADIO_CRCPOLY_MSK;
  NRF_RADIO->CRCPOLY = crc_polynomial;
}

/**
 * Enable a shortcut on the RADIO SHORTS register
 *
 * @param shorts_position: The mask of the shortcuts in the register
 */
void radio_enable_shorts(uint32_t shorts_msk)
{
  NRF_RADIO->SHORTS = 1UL & shorts_msk;
}

/**
 * Disable a shortcut on the RADIO SHORTS register
 */
void radio_disable_shorts()
{
  NRF_RADIO->SHORTS = 0UL;
}

/**
 * Enable a specific interrupts() in the INTENSET RADIO Register
 * 
 * @param interrupt_msk: The mask of the interrupt(s) in the register
 */
void radio_enable_interrupt(uint32_t interrupt_msk)
{
  NRF_RADIO->INTENSET = 1UL & interrupt_msk;
}

/**
 * Disable a specific interrupt in the INTENSET RADIO Register
 */
void radio_disable_interrupts()
{
  NRF_RADIO->INTENSET = 0UL;
}

/**
 * Set the NRF RADIO Peripheral Packet Pointer (Double Buffered)
 */
void set_radio_packet_ptr(uint32_t packet_ptr)
{
  NRF_RADIO->PACKETPTR = packet_ptr;
}

/**
 * Set the radio frequency
 * 
 * @param frequency: X + 2400MHz
 */
inline void set_radio_frequency(uint32_t frequency)
{
  assert(frequency <= 100);

  NRF_RADIO->FREQUENCY = frequency;
}


/**
 * Begin listening for incoming packets
 */
void begin_radio_listen()
{
  NRF_RADIO->TASKS_START = 1UL;
}

/**
 * Start the High Frequency Clock
 */
inline void start_hf_clock()
{
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);
  NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   IRQs
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

volatile bool RADIO_PACKET_RECEIVED = false;

/**
 * RADIO IRQ Handler: Weak Link to be taken here and triggered during END event in SAADC (Enabled elsewhere)
 */
extern "C" void RADIO_IRQHandler_v( void ) {
    // Check to see if the RADIO has completed reception of a packet
    if (NRF_RADIO->EVENTS_END == 1UL)
    {
        NRF_RADIO->EVENTS_END = 0; // Clear the "END" event
        
        RADIO_PACKET_RECEIVED = true; // Start transmission

        RADIO_RX_BUFFER_INDEX_TO_SEND = RADIO_RX_BUFFER_INDEX;

        // This will apply to the next reception sequence (double buffered packet pointer)
        increment_rx_buffer_index();
        set_radio_packet_ptr((uint32_t)(&RADIO_RX_BUFFER[RADIO_RX_BUFFER_INDEX]));
    }
    else
    {
      pinMode(LEDR, OUTPUT);
      digitalWrite(LEDR, LOW);
    }
}


/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
///
///   APPLICATION-SPECIFIC FUNCTIONS
///
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

/**
 * Initialize the Blueooth RADIO Peripheral in the desired configuration for Transmission to the Relay
 */
void init_radio_for_reception()
{ 
  NRF_RADIO->MODE = NRF_2MBIT; // Set to 2Mbps bandwidth

  // Set the PCNF0 & PCNF1 registers
  set_pcnf0(8UL, 0UL, 0UL, 0UL, 0UL, 2UL, 0UL, 0UL);
  set_pcnf1(255UL, 0UL, 4UL, 0UL, 1UL);

  // Set the BASE and PREFIX registers
  set_base0(0xABCDDBF5);
  set_prefix0_ap0(0xEF);
  enable_rxaddress(RADIO_RX_ADDRESS0_POS);
  set_radio_frequency(0x00); // Set to 2400MHz

  // Set the CRCCNF & CRCPOLY Registers
  configure_crc(2UL, 0UL);

  // Set the CRC Polynomial - Utilizing this table:
  //   https://users.ece.cmu.edu/~koopman/crc/
  //    - From Carnegie Mellon University
  set_crc_polynomial(0xd175);

  start_hf_clock();

  // Set the packet
  set_radio_packet_ptr((uint32_t)RADIO_RX_BUFFER);

  radio_enable_shorts(RADIO_SHORTS_END_START_POS);

  radio_enable_interrupt(RADIO_INTENSET_END_MSK | RADIO_INTENSET_ADDRESS_MSK);
  NVIC_SetPriority( RADIO_IRQn, 1UL );
  NVIC_EnableIRQ( RADIO_IRQn );
  
  NRF_RADIO->TASKS_RXEN = 1UL; // Enable the RADIO in RX Mode

  // Wait until the RADIO has begun to move forward with the application
  while(NRF_RADIO->EVENTS_READY == 0UL); 

  begin_radio_listen();  
}