nRF9151 - Low Power Mode

cptel · 2025-08-18T18:13:39+00:00

is the ‘active_sleep’ example on GITS the best example to put the nRF9151 Feather into low power mode? what wakes it up to normal power mode given GPIO is a...

cptel

Took a bit of time to learn how PMIC works and realized that it was never initialized to operate in Hibernate mode.
Please add these 3 lines of code in the ‘deep_sleep’ example prior to calling the hibernate function.

// next 3 API calls should've been part of the init cycle. 
    // However, SHIP_BASE was not initialized ever. 
    // Initializing here to ensure Hibernate mode works as expected
    ret = mfd_npm1300_reg_write(pmic, SHIP_BASE, SHIP_OFFSET_CONFIG, 3U);
    ret = mfd_npm1300_reg_write(pmic, SHIP_BASE, SHIP_OFFSET_LPCONFIG, 0U);
    ret = mfd_npm1300_reg_write(pmic, SHIP_BASE, SHIP_OFFSET_CFGSTROBE, 1U);

    /* set hibernate mode and power down */
    ret = mfd_npm1300_hibernate(pmic, 60000);

I can confidently say that this issue has been resolved

jaredwolff

Can do. Thanks @cptel

jaredwolff

Interesting, these are all the default values. So I guess the write to SHIP_OFFSET_CFGSTROBE is likely the most important? Still not clear why it’s working consistent here and not on your setup. Mystery..

cptel

Per your I2C trace, these values, though default, were transmitted to PMIC prior to setting timeout value and sending hibernate command.
For whatever reason, I did not see those commands sent to PMIC with the NFED/NCS code nor my application that used the NFED/NCS code as you can tell per my I2C capture.

After I added those 3 function calls, the module is entering/exiting Hibernate/ship mode as expected.

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