nrf52 Radio example read always 0

[chinzw]

Hi,

Im not sure if im doing something wrong or what, but i've been hitting a wall when trying to use the radio example transmitter and receiver.

No matter what i send on the transmitter, the receiver always prints out 0. Here's the code that im using:

Transmitter:

#include <nrf52_radio.h>

nrf52 radio;

void setup() {
  #ifdef DEBUG
    Serial.begin(115200);
  #endif

  // SETUP RADIO
  radio.init();
}

void loop()
{
    radio.write(123);
}

Receiver:

#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <nrf52_radio.h>

nrf52 radio;

void setup() {
  Serial.begin(115200);
  radio.init();
}

void loop()
{
  Serial.print("Received packet ");
    uint32_t received = radio.read();
    Serial.print("Received packet ");
    Serial.print(received);
    Serial.print(" ");
    Serial.print(received, HEX);
    Serial.print(" ");
    Serial.println(received, BIN);
}

And here's the "library" i made:

#ifndef NRF52_RADIO_H
#define NRF52_RADIO_H

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

#define PACKET_BASE_ADDRESS_LENGTH  (4UL)                   //!< Packet base address length field size in bytes
#define PACKET_STATIC_LENGTH        (1UL)                   //!< Packet static length in bytes
#define PACKET_PAYLOAD_MAXSIZE      (PACKET_STATIC_LENGTH)  //!< Packet payload maximum size in bytes

class nrf52 {
	public:
		nrf52();
		void init();
		uint32_t read();
		void write(uint32_t packet);
	private:
		uint32_t m_packet;
};

#ifdef __cplusplus
}
#endif

#endif

#include "nrf52_radio.h"
#include "nrf.h"
#include "Arduino.h"

#define PACKET_S1_FIELD_SIZE      (0UL)  /**< Packet S1 field size in bits. */
#define PACKET_S0_FIELD_SIZE      (0UL)  /**< Packet S0 field size in bits. */
#define PACKET_LENGTH_FIELD_SIZE  (0UL)  /**< Packet length field size in bits. */

static uint32_t swap_bits(uint32_t inp);

static uint32_t bytewise_bitswap(uint32_t inp);

static uint32_t swap_bits(uint32_t inp)
{
    uint32_t i;
    uint32_t retval = 0;

    inp = (inp & 0x000000FFUL);

    for (i = 0; i < 8; i++)
    {
        retval |= ((inp >> i) & 0x01) << (7 - i);
    }

    return retval;
}


static uint32_t bytewise_bitswap(uint32_t inp)
{
      return (swap_bits(inp >> 24) << 24)
           | (swap_bits(inp >> 16) << 16)
           | (swap_bits(inp >> 8) << 8)
           | (swap_bits(inp));
}

nrf52::nrf52() {}

void nrf52::init() {
	// Enable the High Frequency clock to the system as a whole
	NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
	NRF_CLOCK->TASKS_HFCLKSTART = 1;
	/* Wait for the external oscillator to start up */
	while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) { }

	// Enables the DC/DC converter when the radio is enabled. Need this!
	NRF_POWER->DCDCEN = 0x00000001;

    // Radio config
    NRF_RADIO->TXPOWER   = (RADIO_TXPOWER_TXPOWER_0dBm << RADIO_TXPOWER_TXPOWER_Pos);
    NRF_RADIO->FREQUENCY = 7UL;  // Frequency bin 7, 2407MHz
    NRF_RADIO->MODE      = (RADIO_MODE_MODE_Nrf_1Mbit << RADIO_MODE_MODE_Pos);

    // Radio address config
    NRF_RADIO->PREFIX0 =
        ((uint32_t)swap_bits(0xC3) << 24) // Prefix byte of address 3 converted to nRF24L series format
      | ((uint32_t)swap_bits(0xC2) << 16) // Prefix byte of address 2 converted to nRF24L series format
      | ((uint32_t)swap_bits(0xC1) << 8)  // Prefix byte of address 1 converted to nRF24L series format
      | ((uint32_t)swap_bits(0xC0) << 0); // Prefix byte of address 0 converted to nRF24L series format

    NRF_RADIO->PREFIX1 =
        ((uint32_t)swap_bits(0xC7) << 24) // Prefix byte of address 7 converted to nRF24L series format
      | ((uint32_t)swap_bits(0xC6) << 16) // Prefix byte of address 6 converted to nRF24L series format
      | ((uint32_t)swap_bits(0xC4) << 0); // Prefix byte of address 4 converted to nRF24L series format

    NRF_RADIO->BASE0 = bytewise_bitswap(0x01234567UL);  // Base address for prefix 0 converted to nRF24L series format
    NRF_RADIO->BASE1 = bytewise_bitswap(0x89ABCDEFUL);  // Base address for prefix 1-7 converted to nRF24L series format

    NRF_RADIO->TXADDRESS   = 0x00UL;  // Set device address 0 to use when transmitting
    NRF_RADIO->RXADDRESSES = 0x01UL;  // Enable device address 0 to use to select which addresses to receive

    // Packet configuration
    NRF_RADIO->PCNF0 = (PACKET_S1_FIELD_SIZE     << RADIO_PCNF0_S1LEN_Pos) |
                       (PACKET_S0_FIELD_SIZE     << RADIO_PCNF0_S0LEN_Pos) |
                       (PACKET_LENGTH_FIELD_SIZE << RADIO_PCNF0_LFLEN_Pos); //lint !e845 "The right argument to operator '|' is certain to be 0"

    // Packet configuration
    NRF_RADIO->PCNF1 = (RADIO_PCNF1_WHITEEN_Disabled << RADIO_PCNF1_WHITEEN_Pos) |
                       (RADIO_PCNF1_ENDIAN_Big       << RADIO_PCNF1_ENDIAN_Pos)  |
                       (PACKET_BASE_ADDRESS_LENGTH   << RADIO_PCNF1_BALEN_Pos)   |
                       (PACKET_STATIC_LENGTH         << RADIO_PCNF1_STATLEN_Pos) |
                       (PACKET_PAYLOAD_MAXSIZE       << RADIO_PCNF1_MAXLEN_Pos); //lint !e845 "The right argument to operator '|' is certain to be 0"

    // CRC Config
    NRF_RADIO->CRCCNF = (RADIO_CRCCNF_LEN_Two << 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
    }
}

uint32_t nrf52::read()
{
	NRF_RADIO->PACKETPTR = (uint32_t)m_packet;
    uint32_t result = 0;

    NRF_RADIO->EVENTS_READY = 0U;
    // Enable radio and wait for ready
    NRF_RADIO->TASKS_RXEN = 1U;

    while (NRF_RADIO->EVENTS_READY == 0U)
    {
        // wait
    }
    NRF_RADIO->EVENTS_END = 0U;
    // Start listening and wait for address received event
    NRF_RADIO->TASKS_START = 1U;

    // Wait for end of packet or buttons state changed
    while (NRF_RADIO->EVENTS_END == 0U)
    {
        // wait
    }

    if (NRF_RADIO->CRCSTATUS == 1U)
    {
        result = m_packet;
    }
    NRF_RADIO->EVENTS_DISABLED = 0U;
    // Disable radio
    NRF_RADIO->TASKS_DISABLE = 1U;

    while (NRF_RADIO->EVENTS_DISABLED == 0U)
    {
        // wait
    }
    return result;
}

void nrf52::write(uint32_t packet)
{
	m_packet = packet;
	NRF_RADIO->PACKETPTR = (uint32_t)m_packet;
    // send the packet:
    NRF_RADIO->EVENTS_READY = 0U;
    NRF_RADIO->TASKS_TXEN   = 1;

    while (NRF_RADIO->EVENTS_READY == 0U)
    {
        // wait
    }
    NRF_RADIO->EVENTS_END  = 0U;
    NRF_RADIO->TASKS_START = 1U;

    while (NRF_RADIO->EVENTS_END == 0U)
    {
        // wait
    }

    NRF_RADIO->EVENTS_DISABLED = 0U;
    // Disable radio
    NRF_RADIO->TASKS_DISABLE = 1U;

    while (NRF_RADIO->EVENTS_DISABLED == 0U)
    {
        // wait
    }
}

[haakonsh]

Hey chinzw,

My first guess is that the CRC check fails. In that event you should receive 0. 

Second guess is that the call to radio.write(123); is invalide because 123 is not declared and therefore its type will be int (int32_t), this is in violation of the maximum payload length that you have set to 1 byte. This should only truncate your payload though, but it's a bug that you are likely to hit sooner or later. 

Third guess is that your empty while() statements are optimized away by your compiler, you should put the CPU to sleep while waiting with the following commands:

__WFE();
__SEV();
__WFE();

Cheers,

Håkon.

[chinzw]

Hi Håkon,

Thanks for replying to my question.

I will try your second and third guesses. First thing i checked was the CRC and that was fine.

[haakonsh]

chinzw said:

First thing i checked was the CRC and that was fine.

How did you check the CRC, I need to know details. 

[chinzw]

I added a Serial.print() inside the CRC check condition.

[haakonsh]

uint32_t nrf52::read()
{
NRF_RADIO->PACKETPTR = (uint32_t)m_packet;

The PACKETPTR is pointing to the address equal to the value of m_packet which is undefined. You need to take the address of m_packet with the '&' operator instead of its content.