How to deal with a case when user takes a battery off while BLE communication?

[joojoo5]

Nrf52832, SDK 13.0 Softdevice 132  PMIC: bq25150

I have a battery powered BLE device. When a user takes off the battery and put it back and powering on, the device does not seem start from MBR (master boot record).

I have a power button that is connected to PMIC and the PMIC will produce 1.8V for the CPU.

My questions are :

  1) Why does it seem not starting from MBR?

  2) Is there a way to start from MBR always whenever power is supplied?

Appreciated if you could help.

[joojoo5]

After more careful investigation, I found that the above statements are not correct.

In fact, the bootloader is executed. However, the speed of execution is different.

See below code.

int main(void)
{
uint32_t ret_val;

(void) NRF_LOG_INIT(NULL);

NRF_LOG_INFO("Inside main\r\n");

nrf_gpio_cfg_output(PIN25LED_RED);

nrf_gpio_pin_set(PIN25LED_RED);
nrf_delay_ms(2000);
nrf_gpio_pin_clear(PIN25LED_RED);

buttons_init();

When it starts from power on button, the red light stayed about 2 seconds.

However, when it starts from NVIC_SystemReset(), then it stayed  little about 2.5 more more seconds.

Can anyone explain why it happens like that?

PS: Please note that I had the delay time of 200ms before and I didn't see the red light. That was why I thought it didn't start from the bootloader. It came more apparent as I put more delay time. Please discard my original questions.

[Håkon Alseth]

Hi,

 

joojoo5 said:

When it starts from power on button, the red light stayed about 2 seconds.

However, when it starts from NVIC_SystemReset(), then it stayed  little about 2.5 more more seconds.

Can anyone explain why it happens like that?

When running on the internal HFCLK, you will see variations up to +/- 6%:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/clock.html?cp=4_2_0_18_3_0#unique_641326801

 

However, if you expect 2 seconds, but see 2.5 seconds in this specific loop:

joojoo5 said:

nrf_gpio_pin_set(PIN25LED_RED);
nrf_delay_ms(2000);
nrf_gpio_pin_clear(PIN25LED_RED);

that is quite strange. Do you measure pulse with a logic analyzer? If yes, can you share the results?

 

Please note that a startup from power-on-reset will take longer than a soft-reset, as the nRF will be kept in reset for a given time period to ensure that VDD is within a valid area:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html?cp=4_2_0_17_9_1#unique_580976277

 

Kind regards,

Håkon