Low Power RFID Solution Demo on the Nordic nRF52 Series

This blog is to use the ESB for building the RFID demo. On every 2 seconds, the PTX would send 4 times RFID data out.

Here is the demo code at the github

https://github.com/jimmywong2003/nrf52-esb-rtc-low-power

static void send_packet(uint8_t *data_ptr, uint32_t length)
{
        static nrf_esb_payload_t esb_payload;
        esb_payload.noack = 0;
        esb_payload.pipe = 0;
        memcpy(esb_payload.data, data_ptr, length);
        esb_payload.length = length;
        nrf_esb_write_payload(&esb_payload);
        tx_packets_loaded++;
}

int main(void)
{
        ret_code_t err_code;
        NRF_POWER->DCDCEN = 1;
        gpio_init();

        err_code = NRF_LOG_INIT(NULL);
        APP_ERROR_CHECK(err_code);
        NRF_LOG_DEFAULT_BACKENDS_INIT();
        hfclock_start();
        rtc_init();
        err_code = esb_init();
        APP_ERROR_CHECK(err_code);
        NRF_LOG_DEBUG("RFID PTX Started.");
        uint8_t esb_packet[4] = {0};
        while (true)
        {
                if(tx_send_packet)
                {
                        hfclock_start();

                        esb_packet[1]++;
                        send_packet(esb_packet, 4);
                        NRF_LOG_DEBUG("tx_send_packet = %d", tx_send_packet);

                        tx_send_packet = false;
                }
                if(tx_packets_loaded == 0)
                {
                        // If the buffers are empty, disable the HF clock to save power
                        hfclock_stop();
                        NRF_LOG_DEBUG("Stop HFCLK");
                }
                NRF_LOG_FLUSH();
                powerdown();
        }
}

The average current consumption of the PTX (measured by Nordic Power Profile Kit) is around 3.6 uA shown as below.