PN7642 - Sleep Mode

[MPEngineering]

Hey guys,

I´m trying to use the PN76_Sys_PCRM_EnterStandby(); Function to sleep. When just telling to sleep until an event on GPIO3 happens everthing is fine.
When trying to use WUC something wents wrong.
There is no Error when turning into sleep, but the IC is waking up directly and I´m not able to figure out why.

Use case is to enter sleep several times to sleep for example 5 minutes.

Logic:

if(calc_sleep_en_b == FALSE)

{

dwWakeUpCntValue = calculate_sleep_time(new_lock_values.public_timer_value);

calculated_public_counter_value_ui = dwWakeUpCntValue;

timer_counter_value_ui = 0;

select_wake_up_reason = E_PN76_PCRM_WAKEUP_SOURCE_GPIO3_LOW | E_PN76_PCRM_WAKEUP_SOURCE_TIMER;

max_sleep_time_li = MAX_SLEEP_TIME;

PCRM_CLEARBITN(PCRM_GPREG6, PHHAL_HW_PN76XX_GPREG_6_LPCD_ENABLED_POS);

status_pn7642 = PN76_Sys_PCRM_EnterStandby(select_wake_up_reason, max_sleep_time_li);

}

else

{

PCRM_CLEARBITN(PCRM_GPREG6, PHHAL_HW_PN76XX_GPREG_6_LPCD_ENABLED_POS);

PN76_Sys_PCRM_ReEnterStandby();

}

After sleeping:

- Check BOOT Regs

- Reset BOOT REG 2 and 3

- if counter value does not equal expected calculatet value sleep again with PN76_Sys_PCRM_ReEnterStandby();

All Variables to check why waking up and the counter are defined in AO-RAM:

__attribute__((section(".noinit.$RAM2"))) volatile uint8_t magic_num;

__attribute__((section(".noinit.$RAM2"))) volatile uint8_t sleep_reason_uc;

__attribute__((section(".noinit.$RAM2"))) volatile uint32_t timer_counter_value_ui;

__attribute__((section(".noinit.$RAM2"))) volatile uint32_t calculated_public_counter_value_ui;

What could cause this problem?

Did i miss something?

Do i have to reset a bit from these regs also?:

• PCRM_SYS_BOOT1_STS
• PCRM_SYS_BOOT2_STS
• PCRM_SYS_BOOT3_STS
• PCRM_SYS_STBY_CFG_REG
• PCRM_SYS_STBY_CFG_REG
• PCRM_SYS_LP_CLK_EN_REG
• PCRM_INT_SET_STATUS_REG
• PCRM_INT_CLR_STATUS_REG

Thanks for helping.

Best regards

Oliver

[MPEngineering]

Hey Edurado,

PN7642 FW is 02.06 and SDK Version is 2.15.004.
Wake Up Counter value is 1023 for 2690 ms.

Low Power Card Detection is not neccessary. Just sleep, compare and iterate the AO-RAM counter if not >=, then sleep again.

Do i have to handle (reset) BOOT Regs, Interrupt Flags (from PCRM Registers) or is this done internally, when entering Standby again? 
Should BOOT_2 Register be 0x00000000 when enter sleep?

I know this pdf, but there is no further information about this. 

Best regards

Oliver

[EduardoZamora]

Hi,

Are you using our Development Kit for PN7642, or is it a custom board?

I can see that you are OR-ing GPIO3 and Timer as wake-up sources. Could you please confirm that configuring only Timer as wake-up source (E_PN76_PCRM_WAKEUP_SOURCE_TIMER) works properly?

Please, try using the nfc_low_power_mode demo from PN7642 SDK, select option 1 -> Enter Standby with Counter as Wakeup, then option 2 -> 2690ms (Low Power Standby Max Interval), and let me know if it is working as expected.

Regards,
Eduardo.

[MPEngineering]

Hi,

It´s a costom Board.
Using only the Timer (E_PN76_PCRM_WAKEUP_SOURCE_TIMER) also doesn´t work.
So logically it works, but the IC never sleeps 2650 ms. In the end the counter equals the expected sleep cycles and switches on an LED.

I flashed the example to the custom Board and it works.

00> 1 PCRM_SYS_STBY_CFG: 0x00000001
00>
00> Boot 1 REG: 0x00000010
00> Boot 2 REG: 0x00000000
00> Boot 3 REG: 0x00000020
00> ---PN7642 IC configuration details---
00> ******************************************************************************
00> *****WARNING***** : PN7642 IC configured with below settings.
00> *****WARNING***** : IC settings MUST match with board settings. If any MISMATCH, it may result in PN7642 IC damage.
00> POWER/DCDC Configuration :
00> DC-DC Usage in card mode : DC-DC is POWERED, not BYPASSED
00> DC-DC Usage in Reader mode : DC-DC is POWERED, not BYPASSED
00> VUP Input Voltage : Internal DC-DC used: with auto by pass and variable boost w.r.t VDDPA
00> DC-DC usage for LPCD : Use of DC-DC for LPCD disabled
00> RFLD/NFCLD Calibration status : NOT Calibrated
00> DPC related configuration :
00> DPC in active target mode : ENABLED
00> DPC in active initiator mode : ENABLED
00> DPC in Reader/Passive Initiator mode : ENABLED
00> Autocoll configuration :
00> Random UID enable : DISABLED. Uses UID stored in EEPROM
00> ******************************************************************************
00>
00> Test_a Variable :0
00>
00> Low Power Mode Example:
00> Boot after Standby with WakeUp counter expiry
00> Boot 2 REG: 0x00000000
00> Boot 3 REG: 0x00000020
00> Test_a Variable :0
00> Select the Modes :
00> 1 -> Enter Standby with Counter as Wakeup :
00> 2 -> Enter Standby with External RF as Wakeup :
00> 3 -> Enter Ultra Low Power Standby with Counter as Wakeup :
00> 4 -> Enter Ultra Low Power Standby with External RF as Wakeup :
00> 5 -> Enter ULPCD Calibration :
00> 6 -> Enter ULPCD Detection :
00> 7 -> Enter LPCD Calibration :
00> 8 -> Enter LPCD Detection:
< 1
00> 1
00> Select the Wake Up interval from below Options :
00> 0 -> 500ms :
00> 1 -> 1000ms :
00> 2 -> 2690ms (Low Power Standby Max Interval) :
00> 3 -> 4095ms (Ultra Low Power Max Interval) :
< 2
00> 2 PCRM_SYS_STBY_CFG: 0x00000001
00>
00> Boot 1 REG: 0x00000010
00> Boot 2 REG: 0x00000000
00> Boot 3 REG: 0x00000020

Can you confirm, that i don´t have to manipulate the Boot Regs, PCRM INT Regs etc?
I think this is done internally (NXP FW / FSM) and your example does not show any handling.

Do you have another idea?

Best regards

Oliver 

[EduardoZamora]

Hi,

As I understand, you can successfully run the nfc_low_power_mode demo from PN7642 SDK when using counter as wake up source, and the Standby mode behaves as expected, is this correct?

Also, your custom implementation is intended to put the PN7642 into Standby mode periodically during a certain amount of time (e.g. device enters standby for 2690 ms. This "wake up -> standby" process is repeated during 5 min), is this also correct? Could you please describe the scenario that would require such application?

When you mention that "the IC never sleeps 2650 ms", does it mean that something is preventing the device to enter Standby? Or is it that the device wakes up before completing the wake up interval?

In your implementation, I can see that you calculate dwWakeUpCntValue = calculate_sleep_time(new_lock_values.public_timer_value). However, you set max_sleep_time_li = MAX_SLEEP_TIME and give this variable as a parameter to PN76_Sys_PCRM_EnterStandby(select_wake_up_reason, max_sleep_time_li). Could you please confirm that MAX_SLEEP_TIME value is valid for parameter dwWakeUpCntValue of N76_Sys_PCRM_EnterStandby?

This is the general sequence for LPCD mode with Standby, it might be a good reference:

Regards,
Eduardo.

[MPEngineering]

Hey,

1. Yes, i can run the nfc_low_power_mode demo on my custom board and it works.

2. I use the PN7642 as standalone uC without a host. It has no real RTC, so i have to put it into sleep periodically. E.g i want to sleep 5 minutes with max sleeping time of 2650 ms -> repeating sleep cycles: 113. So: wake up, check the AO-RAM counter variable. If counter variable is less than 113, count up and sleep again.

3. When i use the API Functions in my Project, like PN76_Sys_PCRM_EnterStandby(), the IC never sleep max time (2,65 s), but is reaching the AO-RAM counter and then runs through code as expected. There is no error when calling the API. Its much to fast.

4. Yes, MAX_SLEEP_TIME is 1023.

5. I dont want to use LPCD Mode. There has to be a possibility to just use the WUC alone together with GPIO3.

Beside this API Problem I tried to not use API Function. Instead I use the PCRM Regs directly. Now the uC sleeps one time (2,65 s), but no second time. I think because something is preventing it, to enter sleep again.
I safed:
- BOOT1 (0x00000000)
- BOOT2 (0x00022000 -> GPIO3 and WUC),
- BOOT3(0x00000000),
- PCRM_INT_ENABLE (0x4060010),
- PCRM_INT_STATUS (0x00000104) in EEPROM. 

I tried to clear BOOT2 through PCRM_SYS_STBY1_CTRL_CLR_BOOT_REGS_MASK and PCRM_SYS_STBY1_CTRL_CLR_RST_STS_MASK, but it has no effect. PCRM_INT_STATUS is a mystery, cause GPIO2_ZIF is not enabled?!

How can i delete prevention flags?

Regards,
Oliver

[EduardoZamora]

Hi,

I am aware that you submitted a support ticket regarding this topic. In order to keep only one channel of communication, please continue the discussion in your internal ticket.

Regards,
Eduardo.

[EduardoZamora]

Hello @MPEngineering

Hope you are doing well.

What are the PN7642 Firmware and SDK versions you are using?

If you are evaluating the low-power features of PN7642, please consider using nfc_examples > nfc_low_power_mode as reference. Also, if you are looking to implement Low Power Card Detection, PN7642 SDK offers Nfcrdlib_Ex6_LPCD project example, which demonstrates all different LPCD options.

Could you please confirm what is the time (or wakeup counter) value you are using? Please consider that max wakeup time is 2690 ms. I will also recommend you referring to How to use the low-power features of the PN76 family NFC controller.

Regards,
Eduardo.