NFC is unstable when DCDEN1 is enabled.

RE: NFC is unstable when DCDEN1 is enabled.

dmq — Sat, 03 Jul 2021 01:52:17 GMT

I seem to have encountered a similar issue as this，I didn't find the errata FTPAN-98.Would you mind show me where to add the follow code?

*(volatile uint32_t *) 0x4000568C = 0x0000702

Thanks!

RE: NFC is unstable when DCDEN1 is enabled.

Jared — Tue, 28 Apr 2020 14:40:54 GMT

Hi,

Ok. I would also state that it's not clear why your Hardfault disappears when you write to that internal register. I also strongly don't recommend writing to any non-documented register as it can potentially damage the chip under certain conditions.

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Tue, 28 Apr 2020 10:50:33 GMT

Hi,

I am doing that as of the moment...

I am trying to build on SDK 16.0.0 to show you that it is not a "hal_nfc_t2t.c" problem. But like I said it is quite impossible to get things done with the pre compiled lib. Now I am using trying out "nrfx_nfct.c" from SDK 16.0.0.

RE: NFC is unstable when DCDEN1 is enabled.

Jared — Mon, 27 Apr 2020 11:39:44 GMT

Hi,

As mentioned in the previous reply, could you share a minimal project that would reproduce the issue?

regards

Jared

RE: NFC is unstable when DCDEN1 is enabled.

Jared — Thu, 23 Apr 2020 07:31:26 GMT

Hi,

I can't really see any reasons for why the Hardfault would disappear as a consequence of you writing to that register. I'm also not confident in that the Hardfault isn't connected to your usage of a customized hal_t2t.c from SDK 15.2.

The register is an internal undocumented register that we unfortunately don't share any information about.
No, the NFCT peripheral is specified at 106 kbps.

I need to discuss this case with some of our developers. I'll get back to you when I have more information. In the meantime, could you provide a minimal project that would reproduce the issue and the steps to reproduce it.

regards

Jared

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Wed, 22 Apr 2020 01:13:24 GMT

Hi Jared,

I found a work around by changing the value of an unknown NFCT register used in errata FTPAN-98.

*(volatile uint32_t *) 0x4000568C = 0x00007029;

This allows me to use DCDCEN1 now.

As stated in my first post, my IC revision is QIAAD0 and it is not affected by FTPAN-98. Initial reading on register 0x4000568C resulted in a value of 0x00038148. I divided this default value by powers of 2 until the hard faults stopped coming. I don't know why this works. I blindly tried other unknown NFCT registers before I found this one.

I believe the problem was related to EasyDMA causing memory corruptions in the RAM. This resulted to invalid values inside the stack and thus causing the hard faults. Hard faults caused the delays in which resulted to NFC communication failures in some timing constrained readers.

Follow up questions:

1. Is it possible for you to tell me what register 0x4000568C actually is?

2. Are there other undocumented NFCT registers that can enable 212 kbps and 424 kbps speeds?

I was checking a very early version of the SDK and I came across these registers:

SHUNT_REG_THRESHOLDS 0x40005610

MOD_STEP_FIXED 0x40005614

MOD_STEP_MULTIPLIER 0x40005618

INITIAL_LOAD_CTRL_VAL 0x40005688

MOD_STEP_FIXED and MOD_STEP_MULTIPLIER sounded like they could be used to adjust the default 106 kbps communication speed. They don't do anything to my IC Revision though.

B.R.

RE: NFC is unstable when DCDEN1 is enabled.

Jared — Mon, 20 Apr 2020 13:52:44 GMT

Hi,

I understand, it seems the hardfaults are coming from the NFC IRQ. I can't see a clear dependency between the DCDC and the NFC peripheral. A possibility would be that the DCDC switching is affecting the HFXO in the form of noise, but i'm not sure on this. Could you provide a minimal project that would reproduce this issue and the steps to reproduce it? I can make the case private if you prefer it :)

regards

Jared

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Sat, 18 Apr 2020 09:11:52 GMT

Hi Jared,

I tried the writable NDEF NFC example in SDK 16.0.0 but it cannot replicate the problem because I believe the NFC traffic is too low.

I don't believe the problem is related to any current NFCT erratas because I have ZERO HARDFAULTS when DCDCEN1 is disabled. If this was related to the supposedly "buggy" NFCT hal_nfc_t2t.c from previous SDKs then I should have the same HARDFAULTS when not using DCDCEN1.

As I developer, I find the NFCT precompiled libs from SDK 16.0.0 very restricting and practically useless for doing anything "productive". My current project can never work with precompiled libs in SDK 16.0.0 that is why I am using SDK 15.2.0.

Anyway, I have imported my project to SDK 16.0.0 but using hal_nfc_t2t.c from SDK 15.2.0 and the same HARDFAULTS appear when DCDCEN1 is again enabled.

Do you have any idea what those hardfaults mean btw?

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Thu, 16 Apr 2020 13:45:58 GMT

Hi Jared,

I will try to replicate it using those precompiled libs on SDK 16.0.

B.R>

RE: NFC is unstable when DCDEN1 is enabled.

Jared — Thu, 16 Apr 2020 12:38:14 GMT

Hi,

Thank you for a good explanation of your issue. I'm not entirely sure in which files the workaround is implemented in SDK 16, but have you implemented the workaround yourself in the custom files? Are you able to reproduce the error with an unmodified (but with DCDC enabled) NFC Tag example from SDK 16.0 that uses the precompiled libs?

best regards

Jared

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Wed, 15 Apr 2020 11:36:59 GMT

Peripherals used:

SPIM3 @ 32Mhz (NRF_SPIM_FREQ_32M)

WDT @ NRF_WDT->CRV = 3 * 32768 ; // 3 sec. timeout

NVMC

app_timer

bsp_board_init(BSP_INIT_LEDS);

bsp_board_init(BSP_INIT_BUTTONS);

while (1)
{
NRF_LOG_FLUSH();
NRF_WDT->RR[0] = WDT_RR_RR_Reload; //Reload watchdog register 0
power_manage();

}

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Wed, 15 Apr 2020 11:05:36 GMT

Hi,

Just to add to this...

I enabled UART logging and I could see that I am getting hardfault errors when DCDEN1 is set to 0x00000001;

<error> hardfault: HARD FAULT at 0x0668D20C
<error> hardfault: R0: 0x00000000 R1: 0x00000006 R2: 0x00000000 R3: 0x00000000
<error> hardfault: R12: 0x0000000C LR: 0x00001849 PSR: 0x01000015
<error> hardfault: Cause: Instruction bus error.

There is not code at 0x0668D20C (obviously)... So why do I get these errors when DCDEN1 is enabled?

The address of the HARD FAULT randomly changes... here are other instances:

<error> hardfault: HARD FAULT at 0x0E7C9248
<error> hardfault: R0: 0x00000000 R1: 0x00000006 R2: 0x00000000 R3: 0x0 0000000
<error> hardfault: R12: 0x0000000C LR: 0x00001849 PSR: 0x01000015
<error> hardfault: Cause: Instruction bus error.

...

<error> hardfault: HARD FAULT at 0x00002B72
<error> hardfault: R0: 0x0000E3AF R1: 0x20000B3C R2: 0x0000FFFE R3: 0x000074C4
<error> hardfault: R12: 0x00000000 LR: 0x00000AA7 PSR: 0x81000015
<error> hardfault: Cause: Data bus error (PC value stacked for the exception return points to the instruction that caused the fault).
<error> hardfault: Bus Fault Address: 0x20008000

...

<error> hardfault: HARD FAULT at 0x68D20D30
<error> hardfault: R0: 0x00000000 R1: 0x00000028 R2: 0x200014CC R3: 0x00000004
<error> hardfault: R12: 0x00000000 LR: 0x000016AF PSR: 0x20000015
<error> hardfault: Cause: Instruction bus error.

Now when I just simply put back DCDEN1 to 0x00000000, the hard faults disappear.

These hard faults were probably the ones causing the FDT issues...

Anyway, how can I fix this problem as I really need to enable DCDEN1 to lower my power consumption.

RE: NFC is unstable when DCDEN1 is enabled.

Brad Roberts — Wed, 15 Apr 2020 10:55:35 GMT

Just