NFC and LFCLK initialization

[LWittland]

I'm experiencing a problem with the NFC.

I'm trying to make a simple read-only tag, and I've used the NFC Text Record Example to build upon. That worked without a problem.

However, when I integrated the NFC code in my project, I wasn't able to read out the tag any more, the reader said it was empty. However, I got no error code from the nfc library/code.

When I shuffled my code around, I found out that the problem has to do with the low frequency clock configuration I used:

void LFCLK_Config(void)
{
    ret_code_t err_code = nrf_drv_clock_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_clock_lfclk_request(NULL);
}

If I configure the LFCLK first, the program runs, but the NFC tag is empty. If i configure the NFC first, I'll get a NRF_ERROR_MODULE_ALREADY_INITIALIZED error from the nrf_drv_clock_init() call. Unfortunately, I need the LFCLK to drive my RTC.

I havn't found anything in the documentation that forbits the use of LFCLK when using NFC (using nRF52840, there shouldn't even be the timer 4 restriction).

Is there a way to solve this?

I'm using a nRF52840 and SDK version 15.

I've found the Patch for nrf_nfct_field_event_handler() function and applied it; it made no difference.

Best regards,

     Lasse

[Simon]

The nrf_drv_clock_init() is already run by the NFC example: fc_t2t_setup(..)-->hal_nfc_setup(..)-->nrf_drv_clock_init().

In the LFCLK_Config() function try to run nrf_drv_clock_init_check() first, and only initialize the clock module if it is not already initialized.

Best regards,

Simon

[LWittland]

Hello Simon,

I don't have to check if the clock module is initialized; when I initialize the NFC first, it always is.

Not executing the code in LFCLK_config() doesn't do what I need:

Skipping

ret_code_t err_code = nrf_drv_clock_init();

let's me use the LFCLK for my application; the NFC tag is readable, but empty.

Also skipping

nrf_drv_clock_lfclk_request(NULL);

the Tag is readable and contains the data I configured with NFC_NDEF_TEXT_RECORD_DESC_DEF, but the LFCLK isn't avaliable (more precisely: my RTC handler won't be called).

[Simon]

Did you resolve the issue?

[LWittland]

No.

I still have no Idea what I can do to use the LFCLK both for NFC and the RTC.

I have tried to run the RTC from the Systick Timer instead of LFCLK, but that caused problems with other parts of our application, so this not an option either.

Also, since the soft device uses up RTC channels 0 and 1, I am limited to RTC chanel 2.

Any Ideas?