Low level 802.15.4 transmit code

[DU_Radio]

I am trying to make a simple MAC-layer transceiver using Arduino environment.  I have some code derived from this example: https://github.com/IoTS-P/nRF52-802154-Raw-Transmitter
and have discovered that it hangs after one to a few hundred transmissions.  I have gone over the datasheet for the 802.15.4 radio section and I do not see where the problem is.I am using a Zena receiver to monitor the transmissions.  I noticed that the CCA appears to take some tens-of-mS fairly often while the Zena does not show any other messages arrived during that time.  What am I doing wrong with the radio hardware?

<project files attached>

[DU_Radio]

My uploaded files went to some bit bucket.  Here is the cleaned up code (3 files):

//Raw802.ino
#include <Arduino.h>
#include <stdint.h>
//#include <stdbool.h>
#include "radio.h"
#include <nrf52840.h>
#include <Adafruit_TinyUSB.h>// Seems to need this without Serial or USB. Maybe DFU boot loader needs it?

#define PIN_LEDX 22 // Red LED

// channel 
#define DEFAULT_INITIAL_CHANNEL 19

// read buffer  
uint8_t *rx_buffer;
uint8_t u8SeqNum = 0;
// the frame length in phy layer header 
uint8_t pkt_len = 0;
uint8_t u8PktBuf[100];

// has data transmitting
uint8_t bTransmitting = false;

// packets
#define MAX_PKTS_IN 12 // Maximum packets in the queue
struct __attribute__((packed)) packets_structure
{
  uint16_t size[MAX_PKTS_IN] = {0};
  uint8_t *pkt_buffer[MAX_PKTS_IN];
  uint8_t head = 0;
  uint8_t tail = 0;
} packets;

// channel
uint8_t radio_channel = DEFAULT_INITIAL_CHANNEL;


/**
 * nRF51822 RADIO handler.
 *
 * This handler is called whenever a RADIO event occurs (IRQ).
 **/
extern "C" void RADIO_IRQHandler(void)
{
  // if (NRF_RADIO->EVENTS_FRAMESTART)
  if (*(uint32_t *)(0x40001138)) //Events-FrameStart
  {
    *(uint32_t *)(0x40001138) = 0;
  }

  if (NRF_RADIO->EVENTS_READY)
  {
    NRF_RADIO->EVENTS_READY = 0;
    NRF_RADIO->TASKS_START = 1;
  }

  if (NRF_RADIO->EVENTS_END)
  {
    NRF_RADIO->EVENTS_END = 0;
    // NRF_RADIO->TASKS_START = 1;
    // If transmitt end
    if (bTransmitting)
    {
      bTransmitting = false;
      //Serial.write("SENDED ");
       //radio_tx_to_rx();
      //return;// maybe interrupt needs special return?
      goto exit;
    }
  }
  if (*(uint32_t *)(0x40001148))//CCA-Busy
  {
    Serial.println("CCABUSY");
    *(uint32_t *)(0x40001148) = 0;
    NRF_RADIO->TASKS_DISABLE = 1;
    while (NRF_RADIO->EVENTS_DISABLED == 0);
    //Serial.println("CCABUSY: disable the radio");
    sig_ccabusy = true;
  }
  if (*(uint32_t *)(0x4000114C))
  {
    Serial.println("CCASTOPPED");
  }
  if (*(uint32_t *)(0x40001144))//CCA-IDLE
  {
    Serial.println("CCAIDLE");
    sig_ccabusy = false;
    *(uint32_t *)(0x40001144) = 0;
    // NRF_RADIO->TASKS_CCASTART = 0
    //*(uint32_t *)(0x4000102c) = 1;
  }
  exit:
  {
  
  }
}

void setup()
{
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(PIN_LEDX, OUTPUT); // Going for the RED Led now
  Serial.begin(115200);
  rx_buffer = (uint8_t *)malloc(IEEE802154_FRAME_LEN_MAX + 3);

  radio_set_sniff(radio_channel, 0); // Setup the radio
}

uint32_t ctr = 0;
void loop()
{
  if (NRF_RADIO->EVENTS_READY)
  {
    NRF_RADIO->EVENTS_READY = 0;
    // NRF_RADIO->TASKS_START;
  }
  delay(1);
  ctr++;
  if(ctr > 900)// Transmit every 200mS
  {
    ctr = 0;
    pkt_len = 17; 
    memcpy(u8PktBuf, "\x11\x00\x00\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff",19);
    u8PktBuf[3] = u8SeqNum++;
  }


  // memcpy pkt_buffer to tx_buffer
  if (!bTransmitting && pkt_len)
  {
    Serial.write(".");
    digitalWrite(PIN_LEDX, HIGH);
    bTransmitting = true;
    radio_send_custom(u8PktBuf, radio_channel);
    pkt_len = 0;
    digitalWrite(PIN_LEDX, LOW);
  }
}

//radio.cpp
#include "radio.h"
#include <Arduino.h>
#include <assert.h>

// signal for CCABUSY
volatile uint8_t sig_ccabusy = false;

/**
 * channel_to_freq(int channel)
 *
 * Convert a BLE channel number into the corresponding frequency offset
 * for the nRF51822.
 **/
uint8_t channel_to_freq(int channel) {
  assert(channel > 10);
  assert(channel < 27);
  return 5 * (channel - 10);
}

/**
 * radio_disable()
 *
 * Disable the radio.
 **/

void radio_disable(void) {
  if (NRF_RADIO->STATE > 0) {
    NVIC_DisableIRQ(RADIO_IRQn);

    NRF_RADIO->EVENTS_DISABLED = 0;
    NRF_RADIO->TASKS_DISABLE = 1;
    while (NRF_RADIO->EVENTS_DISABLED == 0);
  }
}

/**
 * @brief   Convert from dBm to the internal representation, when the
 *          radio operates as a IEEE802.15.4 transceiver.
 */
static inline uint8_t _dbm_to_ieee802154_hwval(int8_t dbm) {
  return ((dbm - ED_RSSIOFFS) / ED_RSSISCALE);
}

static int set_cca_threshold(int8_t threshold) {

  if (threshold < ED_RSSIOFFS) {
    return -1;
  }

  uint8_t hw_val = _dbm_to_ieee802154_hwval(threshold);

   NRF_RADIO->CCACTRL &= ~RADIO_CCACTRL_CCAEDTHRES_Msk;
  //*(uint32_t *)(0x4000166c) &= ~RADIO_CCACTRL_CCAEDTHRES_Msk;

   NRF_RADIO->CCACTRL |= hw_val << RADIO_CCACTRL_CCAEDTHRES_Pos;
  //*(uint32_t *)(0x4000166c) |= hw_val << RADIO_CCACTRL_CCAEDTHRES_Pos;
  return 0;
}

/**
 * radio_set_sniff(int channel)
 *
 * Configure the nRF51822 to sniff on a specific channel.
 **/

void radio_set_sniff(int channel, uint32_t access_address) {
  // Disable radio
  radio_disable();

  // Enable the High Frequency clock on the processor. This is a pre-requisite
  // for the RADIO module. Without this clock, no communication is possible.
  NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
  NRF_CLOCK->TASKS_HFCLKSTART = 1;
  while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

  // power should be one of: -30, -20, -16, -12, -8, -4, 0, 4
  NRF_RADIO->TXPOWER = RADIO_TXPOWER_TXPOWER_Neg20dBm;//Pos4dBm;
  NRF_RADIO->TXADDRESS = 0;

  /* Set 802154 data rate. */
  NRF_RADIO->MODE = RADIO_MODE_MODE_Ieee802154_250Kbit;
  /* Listen on channel . */
  NRF_RADIO->FREQUENCY = channel_to_freq(channel);

  /* set start frame delimiter */
   //NRF_RADIO->RESERVED12[4] = IEEE802154_SFD;// Gets a read-only error on ths
  *(uint32_t *)(0x40001660) = IEEE802154_SFD;

  /* set MHR filters */
   NRF_RADIO->MHRMATCHCONF = 0;         /* Search Pattern Configuration */
  //*(uint32_t *)(0x40001644) = 0;

   NRF_RADIO->MHRMATCHMAS = 0xff0007ff; /* Pattern mask */
  //*(uint32_t *)(0x40001648) = 0xff0007ff;

  /* and set some fitting configuration */
  NRF_RADIO->PCNF0 = ((8 << RADIO_PCNF0_LFLEN_Pos) |
                      (RADIO_PCNF0_PLEN_32bitZero << RADIO_PCNF0_PLEN_Pos) |
                      (RADIO_PCNF0_CRCINC_Include << RADIO_PCNF0_CRCINC_Pos));

  NRF_RADIO->PCNF1 = IEEE802154_FRAME_LEN_MAX;

  NRF_RADIO->MODECNF0 |=
      RADIO_MODECNF0_RU_Fast; // Enable fast mode for radio ramp up

  // Enable CRC
  NRF_RADIO->CRCCNF =
      ((RADIO_CRCCNF_LEN_Two << RADIO_CRCCNF_LEN_Pos) |
       (RADIO_CRCCNF_SKIPADDR_Ieee802154 << RADIO_CRCCNF_SKIPADDR_Pos));
  NRF_RADIO->CRCPOLY = 0x11021;
  NRF_RADIO->CRCINIT = 0;

  // DATAWHITE
  NRF_RADIO->DATAWHITEIV = 0x40;

  NRF_RADIO->PACKETPTR = (uint32_t)(rx_buffer);

  // configure CCA
  set_cca_threshold(CONFIG_IEEE802154_CCA_THRESH_DEFAULT);

  // Configure interrupts
  NRF_RADIO->INTENSET = RADIO_INTENSET_END_Msk | RADIO_INTENSET_FRAMESTART_Msk |
                        // RADIO_INTENSET_CCAIDLE_Msk |
                        RADIO_INTENSET_CCABUSY_Msk;
  // Enable NVIC Interrupt for Radio
  NVIC_SetPriority(RADIO_IRQn, IRQ_PRIORITY_LOW);
  NVIC_ClearPendingIRQ(RADIO_IRQn);
  NVIC_EnableIRQ(RADIO_IRQn);

  // Enable receiver hardware
  NRF_RADIO->EVENTS_READY = 0;
  NRF_RADIO->TASKS_RXEN = 1;
  while (NRF_RADIO->EVENTS_READY == 0);
  NRF_RADIO->EVENTS_END = 0;
  NRF_RADIO->TASKS_START = 1;
}

/**
 * Send raw data asynchronously.
 **/

void radio_send_custom(uint8_t *pBuffer, uint8_t channel) {

  /* No shortcuts on disable. */
  NRF_RADIO->SHORTS = 0x0;
  /* Switch radio to TX. */
  radio_disable();

  for (size_t try_ = 0; try_ < MAX_RETRIES; try_++) 
  {
    /* Switch packet buffer to tx_buffer. */
    NRF_RADIO->PACKETPTR = (uint32_t)pBuffer;
    NRF_RADIO->INTENSET = (1 << RADIO_INTENSET_END_Pos);
    NVIC_ClearPendingIRQ(RADIO_IRQn);
    NVIC_EnableIRQ(RADIO_IRQn);

    NRF_RADIO->EVENTS_READY = 0;
    NRF_RADIO->TASKS_RXEN = 1;
    Serial.write("While 1 ");// NEEDS THIS DELAY
    while (!NRF_RADIO->EVENTS_READY);

     NRF_RADIO->EVENTS_CCAIDLE = 0;
    //*(uint32_t *)(0x40001144) = 0;
    NRF_RADIO->TASKS_CCASTART = 1;
    //*(uint32_t *)(0x4000102c) = 1;

     Serial.write("While 2 "); // Needs this delay
    // while(!(NRF_RADIO->EVENTS_CCAIDLE || CCABUSY));
    while(!(NRF_RADIO->EVENTS_CCAIDLE || NRF_RADIO->EVENTS_CCABUSY));
    // wait for CCAIDLE or CCABUSY
    Serial.write("While 3 ");
    while (!(*(uint32_t *)(0x40001144) || sig_ccabusy));//CCA_IDLE
    if (sig_ccabusy) 
    {
      Serial.println("WARNING: retry for CCABUSY");
      sig_ccabusy = false;
      delay(100);
      continue;
    }

    /* Transmit with max power. */
    NRF_RADIO->TXPOWER =
        (RADIO_TXPOWER_TXPOWER_Pos4dBm << RADIO_TXPOWER_TXPOWER_Pos);
    NRF_RADIO->FREQUENCY = channel_to_freq(channel);

    // enable receiver
    NRF_RADIO->EVENTS_READY = 0;
    NRF_RADIO->TASKS_TXEN = 1;

     Serial.write("While 4\r\n");//needs this delay
    while (!NRF_RADIO->EVENTS_READY);
    NRF_RADIO->TASKS_START = 1;
    /* From now, radio will send data and notify the result to Radio_IRQHandler */
    return;
  }
  Serial.println("ERROR: retry too many times");
}

/**
 * Change radio from TX to RX, while keeping last configuration of
 *radio_send_custom or radio_set_sniff
 **/
void radio_tx_to_rx() {
  NRF_RADIO->PACKETPTR = (uint32_t)(rx_buffer);
  NVIC_DisableIRQ(RADIO_IRQn);
  NRF_RADIO->SHORTS = RADIO_SHORTS_READY_START_Msk;

  // NRF_RADIO->INTENSET = 0;
  NVIC_ClearPendingIRQ(RADIO_IRQn);
  NVIC_EnableIRQ(RADIO_IRQn);

  NRF_RADIO->EVENTS_DISABLED = 0;
  NRF_RADIO->TASKS_DISABLE = 1;

  while (NRF_RADIO->EVENTS_DISABLED == 0);

  NRF_RADIO->EVENTS_READY = 0;
  NRF_RADIO->TASKS_RXEN = 1;
}

//radio.h
/**
 * Radio module
 *
 * This module provides all the required functions to manage the nRF51822
 * transceiver.
 **/

#pragma once
#include <Arduino.h>

extern uint8_t *rx_buffer; /* Rx buffer used by RF to store packets. */

#define IRQ_PRIORITY_HIGHEST 0
#define IRQ_PRIORITY_HIGH 1
#define IRQ_PRIORITY_MEDIUM 2
#define IRQ_PRIORITY_LOW 3

#define RADIO_MODE_MODE_Ieee802154_250Kbit (15UL)


#define IEEE802154_FRAME_LEN_MAX (127U)   /**< maximum 802.15.4 frame length */
#define IEEE802154G_FRAME_LEN_MAX (2047U) /**< maximum 802.15.4g-2012 frame length */
#define IEEE802154_ACK_FRAME_LEN (5U)     /**< ACK frame length */
#define IEEE802154_FCS_LEN                  (2U)


#define RADIO_PCNF0_PLEN_32bitZero (2UL) /*!< 32-bit zero preamble - used for IEEE 802.15.4 */
#define RADIO_PCNF0_CRCINC_Include (1UL) /*!< LENGTH includes CRC */
#define RADIO_PCNF0_CRCINC_Pos (26UL) /*!< Position of CRCINC field. */
#define RADIO_CRCCNF_SKIPADDR_Ieee802154 (2UL) /*!< CRC calculation as per 802.15.4 standard. Starting at first byte after length field. */


#define RADIO_INTENSET_FRAMESTART_Pos (14UL) /*!< Position of FRAMESTART field. */
#define RADIO_INTENSET_FRAMESTART_Msk (0x1UL << RADIO_INTENSET_FRAMESTART_Pos) /*!< Bit mask of FRAMESTART field. */
#define RADIO_INTENSET_CCAIDLE_Pos (17UL) /*!< Position of CCAIDLE field. */
#define RADIO_INTENSET_CCAIDLE_Msk (0x1UL << RADIO_INTENSET_CCAIDLE_Pos) /*!< Bit mask of CCAIDLE field. */
#define RADIO_INTENSET_CCABUSY_Pos (18UL) /*!< Position of CCABUSY field. */
#define RADIO_INTENSET_CCABUSY_Msk (0x1UL << RADIO_INTENSET_CCABUSY_Pos) /*!< Bit mask of CCABUSY field. */


#define ED_RSSISCALE        (4U)    /**< RSSI scale for internal HW value */
#define ED_RSSIOFFS         (-92)   /**< RSSI offset for internal HW value */

/**
 * @brief IEEE802.15.4 default value for CCA threshold (in dBm)
 */
#ifndef CONFIG_IEEE802154_CCA_THRESH_DEFAULT
#define CONFIG_IEEE802154_CCA_THRESH_DEFAULT       (-70)
#endif

/* Bits 15..8 : CCA energy busy threshold. Used in all the CCA modes except CarrierMode. */
#define RADIO_CCACTRL_CCAEDTHRES_Pos (8UL) /*!< Position of CCAEDTHRES field. */
#define RADIO_CCACTRL_CCAEDTHRES_Msk (0xFFUL << RADIO_CCACTRL_CCAEDTHRES_Pos) /*!< Bit mask of CCAEDTHRES field. */

/**
 * @brief   Default start frame delimiter
 */
#define IEEE802154_SFD (0xa7)

// signal for CCABUSY
extern volatile uint8_t sig_ccabusy;
// max retries
#define MAX_RETRIES 5

// functions
uint8_t channel_to_freq(int channel);
void radio_disable(void);
void radio_set_sniff(int channel, uint32_t access_address);
void radio_send_custom(uint8_t *pBuffer, uint8_t channel);
void radio_tx_to_rx();