High power comsumption with nfc while device is on the antenna

RE: High power comsumption with nfc while device is on the antenna

Simonr — Fri, 08 Sep 2023 11:22:40 GMT

So after a bit of digging on my end, I think the current consumption you're seeing is the current draw from the NFCT peripheral in the ACTIVATED state. I am currently waiting for an answer from the developers for a confirmation on whether this is the case or not though.

My colleague Stian explains this in detail (for the nRF52832) in this case. The current we're seeing on the nRF5340 is much lower, but I believe this is due to fixes and improvements to the peripheral as a whole.

Best regards,

Simon

RE: High power comsumption with nfc while device is on the antenna

Seb-labs — Wed, 06 Sep 2023 08:16:47 GMT

Tried with this device tree overlay :

&uart0 {
    status = "disabled";
};
&uart1 {
    status = "disabled";
};
&spi1 {
    status = "disabled";
};
&spi2 {
    status = "disabled";
};
&spi3 {
    status = "disabled";
};
&spi4 {
    status = "disabled";
};
&qspi {
    status = "disabled";
};
&i2c1 {
    status = "disabled";
};
&i2c0 {
    status = "disabled";
};

&nrf700x {
    status = "disabled";
};

&nrf_radio_coex {
    status = "disabled";
};

&gpio_fwd {
    status = "disabled";
};

&led1 {
    status = "disabled";
};

&button0 {
    status = "disabled";
};

&button1 {
    status = "disabled";
};

&led0 {
    status = "disabled";
};

&ficr {
    status = "disabled";
};

&usbd {
    status = "disabled";
};

&wdt {
    status = "disabled";
};

&gpio_fwd {
    uart {
        status = "disabled";
    };
};

&pwm0 {
    status = "disabled";
};

Same result:

RE: High power comsumption with nfc while device is on the antenna

Simonr — Wed, 06 Sep 2023 06:48:25 GMT

I'd suggest checking the device tree of this project. By default, the record_text app enables multiple peripherals that could be the culprit for this extra current consumption.

The DeviceTree extension in VS code lets you see what peripherals are enabled, so you can try disabling all peripherals not in use to see if that helps on your end. If that doesn't help I'll need to ask the devs internally what this extra current could be.

Best regards,

Simon

RE: High power comsumption with nfc while device is on the antenna

Seb-labs — Mon, 04 Sep 2023 14:00:01 GMT

Steps to produce:

1/ take nrf/samples/record_text app (sdk-nrf)

2/ disable uart0 in overlay

3/ patch main.c:

index ff4d5f2e9..b2678ce80 100644
--- a/samples/nfc/record_text/src/main.c
+++ b/samples/nfc/record_text/src/main.c
@@ -40,6 +40,11 @@ static const uint8_t pl_code[] = {'P', 'L'};
/* Buffer used to hold an NFC NDEF message. */
static uint8_t ndef_msg_buf[NDEF_MSG_BUF_SIZE];

+static void stop_nfc_handler(struct k_work *work) {
+       nfc_t2t_emulation_stop();
+       nfc_t2t_done();
+}
+static K_WORK_DELAYABLE_DEFINE(stop_nfc, stop_nfc_handler);

static void nfc_callback(void *context,
                         nfc_t2t_event_t event,
@@ -57,6 +62,9 @@ static void nfc_callback(void *context,
        case NFC_T2T_EVENT_FIELD_OFF:
                dk_set_led_off(NFC_FIELD_LED);
                break;
+       case NFC_T2T_EVENT_DATA_READ:
+               k_work_schedule(&stop_nfc, K_MSEC(100));
+               break;
        default:
                break;
        }

Result:

RE: High power comsumption with nfc while device is on the antenna

Simonr — Mon, 04 Sep 2023 10:40:04 GMT

Okay, I didn't catch that you were calling the nfc_t2t_done() function already. But okay, then something else must still be running on your side. Since the nfc_t2t_done() uninits the NFC peripheral, maybe the NFC initializes some other peripheral on your end. Like a serial function, or the application is handling the incoming data somehow. There must be a thread still running causing this extra current consumption, but without seeing your code/project it's hard to see what's happening exactly and what the current could be.

Best regards,

Simon

RE: High power comsumption with nfc while device is on the antenna

Seb-labs — Fri, 01 Sep 2023 11:48:59 GMT

As I said, if I call nfc_t2t_done() before FIELD_OFF, the consumption go to 80 µA and stay at this value even if the phone is removed from the antenna.

I would like to retrieve the original 8 µA consumption.

RE: High power comsumption with nfc while device is on the antenna

Simonr — Fri, 01 Sep 2023 11:46:15 GMT

Since the NFC_T2T_EVENT_FIELD_ON means that the "NFC tag has detected an external NFC field and was selected by an NFC polling device" I think it keeps the CPU on the nRF5340 running/awake so it can transmit/receive data, and the NFC peripheral won't release the CPU until anNFC_T2T_EVENT_FIELD_OFF or NFC_T2T_EVENT_STOPPED has been called. I think you can call nfc_t2t_done() to stop the NFC peripheral when you're done receiving from the NFC reader instead of waiting for the FIELD_OFF event when it's removed.

Best regards,

Simon