Low power mode running MyNewt on nrf52832 DK

[Min-Ching Ho]

Hi,

    I'm working on putting our system into low power idle mode. We use MyNewt to build our application. In order to get to the lowest power, I disabled BLE and all our drivers except UART for console and debug messages. We have a command that can shut off a bunch of stuff and call __WFE and __SEV(). The code is tested on a nrf52DK(PCA10040 1.2.4, 2018.23). I checked the current on P22 on the board and the measurement was 270uA @ 3.8V from external power supply. This is far away from what your data sheet described. I have checked the setting everywhere and can not figure out what else I need to turn off. Can you please provide some suggestion where I should check? 

Thank you,

Min-Ching

[Sigurd]

Hi,

except UART for console and debug messages.

UART peripheral requires HFCLK and if you run HFCLK with the 64MHz crystal current consumption will be ~250uA.

[Min-Ching Ho]

Hi Siguard, 

    Thanks for the info. It looks like my HFCLK is still up and running. One thing I didn't mentioned in my original post is I did disable UART before WFE. Is there a way to check which peripheral is still using HFCLK? 

Thank you,

Min-Ching

[Sigurd]

Could you try to stop the UART transmitter/receiver, before disabling it ?

NRF_UARTE0->TASKS_STOPRX = 1;
NRF_UARTE0->TASKS_STOPTX = 1;

[Min-Ching Ho]

Hi Siguard,

    Sorry for late reply. I was out of office. I already tried this. It didn't work. I still see the current is >270uA. 

Any other suggestions?

Min-Ching

[Min-Ching Ho]

I would like to share my test code here. FYI.

enter_sleep_mode_cb(struct os_event *ev)

{

    power_mode_e state = *(power_mode_e *)ev->ev_arg;

    if(state == POWER_STATE_NONE)

    {

        // overwrite the power state

        ;

    }

    // call hal power API

    hal_bsp_power_state(state);

    //1. put peripheral into sleep

    // excluded all driver code for test

    // Turn off UART/SPI/I2C

    hal_uart_stop_tx(0);

    hal_uart_stop_rx(0);

    // uart is turned off here by os_dev_suspend_all

    os_dev_suspend_all(0xFFFFFFFF, 1);

    // turn off timer

    hal_timer_deinit(0);

    hal_timer_deinit(1);

    hal_timer_deinit(2);

    hal_timer_deinit(3);

    hal_timer_deinit(4);

    //disable i2c

    hal_i2c_disable(0);

    //disable spi

    hal_spi_disable(1);

    // turn off GPIOE

    //something new from mynewt

    NRF_CLOCK->TASKS_HFCLKSTOP = 1;

    //2. put CPU into wait for event mode

    // Wait for an event

    __WFI();

    // clear the internal event register

    __SEV();

    __WFI();

    //3. wake up process

    // enable UART/SPI/I2C

    //4. wake up complete

    //console_printf("System awake\r\n");

}

[Min-Ching Ho]

I have figured the root cause after I got some help from local FAE team. But, the solution is not clear now.

The SPIM1 actually prevent the system turning off HFXO. It came down to a function call we used in our driver. In MyNewt project, it offers several APIs to write/read the data via SPI. You can find the code here: https://github.com/apache/mynewt-core/blob/master/hw/mcu/nordic/nrf52xxx/src/hal_spi.c. One way is to write byte by byte and poll the status, “hal_spi_txrx()”. The other way is to leverage TASKS, “hal_spi_txrx_noblock()”. Still waiting for further information.

Min-Ching

[Min-Ching Ho]

Got an answer for this one from FAE. I hit Erratum 89.

https://www.nordicsemi.com/DocLib/Content/Errata/nRF52832_Rev2/latest/ERR/nRF52832/Rev2/latest/anomaly_832_89

There is another post on the forum also point out the same thing. 

https://devzone.nordicsemi.com/f/nordic-q-a/42145/spim-easydma-to-increase-power-consumption/163946#163946

After I applied the workaround, the current went down. 

FYI.

Min-Ching