RE: Implementing ACK in software ESB

bjorn-spockeli — Thu, 05 Mar 2020 15:04:17 GMT

Hi Cwmoreiras,

just out of curiosity, why can't you use the ESB implementation in our SDK? It is backwards compatible with the nRF24, see Backward compatibility

Looking at our ESB implementation I found the following functions

static void update_rf_payload_format_esb_dpl(uint32_t payload_length)
{
#if (NRF_ESB_MAX_PAYLOAD_LENGTH <= 32)
    // Using 6 bits for length
    NRF_RADIO->PCNF0 = (0 << RADIO_PCNF0_S0LEN_Pos) |
                       (6 << RADIO_PCNF0_LFLEN_Pos) |
                       (3 << RADIO_PCNF0_S1LEN_Pos) ;
#else
    // Using 8 bits for length
    NRF_RADIO->PCNF0 = (0 << RADIO_PCNF0_S0LEN_Pos) |
                       (8 << RADIO_PCNF0_LFLEN_Pos) |
                       (3 << RADIO_PCNF0_S1LEN_Pos) ;
#endif
    NRF_RADIO->PCNF1 = (RADIO_PCNF1_WHITEEN_Disabled    << RADIO_PCNF1_WHITEEN_Pos) |
                       (RADIO_PCNF1_ENDIAN_Big          << RADIO_PCNF1_ENDIAN_Pos)  |
                       ((m_esb_addr.addr_length - 1)    << RADIO_PCNF1_BALEN_Pos)   |
                       (0                               << RADIO_PCNF1_STATLEN_Pos) |
                       (NRF_ESB_MAX_PAYLOAD_LENGTH      << RADIO_PCNF1_MAXLEN_Pos);
}


static void update_rf_payload_format_esb(uint32_t payload_length)
{
    NRF_RADIO->PCNF0 = (1 << RADIO_PCNF0_S0LEN_Pos) |
                       (0 << RADIO_PCNF0_LFLEN_Pos) |
                       (1 << RADIO_PCNF0_S1LEN_Pos);

    NRF_RADIO->PCNF1 = (RADIO_PCNF1_WHITEEN_Disabled    << RADIO_PCNF1_WHITEEN_Pos) |
                       (RADIO_PCNF1_ENDIAN_Big          << RADIO_PCNF1_ENDIAN_Pos)  |
                       ((m_esb_addr.addr_length - 1)    << RADIO_PCNF1_BALEN_Pos)   |
                       (payload_length                  << RADIO_PCNF1_STATLEN_Pos) |
                       (payload_length                  << RADIO_PCNF1_MAXLEN_Pos);
}

Also looking at the NRF_ESB_PROTOCOL_ESB_DPL case in start_tx_transaction() might offer some clues.

static void start_tx_transaction()
{
    bool ack;

    m_last_tx_attempts = 1;
    // Prepare the payload
    mp_current_payload = m_tx_fifo.p_payload[m_tx_fifo.exit_point];


    switch (m_config_local.protocol)
    {
        case NRF_ESB_PROTOCOL_ESB:
            update_rf_payload_format(mp_current_payload->length);
            m_tx_payload_buffer[0] = mp_current_payload->pid;
            m_tx_payload_buffer[1] = 0;
            memcpy(&m_tx_payload_buffer[2], mp_current_payload->data, mp_current_payload->length);

            NRF_RADIO->SHORTS   = m_radio_shorts_common | RADIO_SHORTS_DISABLED_RXEN_Msk;
            NRF_RADIO->INTENSET = RADIO_INTENSET_DISABLED_Msk | RADIO_INTENSET_READY_Msk;

            // Configure the retransmit counter
            m_retransmits_remaining = m_config_local.retransmit_count;
            on_radio_disabled = on_radio_disabled_tx;
            m_nrf_esb_mainstate = NRF_ESB_STATE_PTX_TX_ACK;
            break;

        case NRF_ESB_PROTOCOL_ESB_DPL:
            ack = !mp_current_payload->noack || !m_config_local.selective_auto_ack;
            m_tx_payload_buffer[0] = mp_current_payload->length;
            m_tx_payload_buffer[1] = mp_current_payload->pid << 1;
            m_tx_payload_buffer[1] |= mp_current_payload->noack ? 0x00 : 0x01;
            memcpy(&m_tx_payload_buffer[2], mp_current_payload->data, mp_current_payload->length);

            // Handling ack if noack is set to false or if selective auto ack is turned off
            if (ack)
            {
                NRF_RADIO->SHORTS   = m_radio_shorts_common | RADIO_SHORTS_DISABLED_RXEN_Msk;
                NRF_RADIO->INTENSET = RADIO_INTENSET_DISABLED_Msk | RADIO_INTENSET_READY_Msk;

                // Configure the retransmit counter
                m_retransmits_remaining = m_config_local.retransmit_count;
                on_radio_disabled = on_radio_disabled_tx;
                m_nrf_esb_mainstate = NRF_ESB_STATE_PTX_TX_ACK;
            }
            else
            {
                NRF_RADIO->SHORTS   = m_radio_shorts_common;
                NRF_RADIO->INTENSET = RADIO_INTENSET_DISABLED_Msk;
                on_radio_disabled   = on_radio_disabled_tx_noack;
                m_nrf_esb_mainstate = NRF_ESB_STATE_PTX_TX;
            }
            break;

        default:
            // Should not be reached
            break;
    }

    NRF_RADIO->TXADDRESS    = mp_current_payload->pipe;
    NRF_RADIO->RXADDRESSES  = 1 << mp_current_payload->pipe;

    NRF_RADIO->FREQUENCY    = m_esb_addr.rf_channel;
    NRF_RADIO->PACKETPTR    = (uint32_t)m_tx_payload_buffer;

    NVIC_ClearPendingIRQ(RADIO_IRQn);
    NVIC_EnableIRQ(RADIO_IRQn);

    NRF_RADIO->EVENTS_ADDRESS = 0;
    NRF_RADIO->EVENTS_PAYLOAD = 0;
    NRF_RADIO->EVENTS_DISABLED = 0;

    DEBUG_PIN_SET(DEBUGPIN4);
    NRF_RADIO->TASKS_TXEN  = 1;
}

Best regards

Bjørn