High power consumption when using SPIM3

RE: High power consumption when using SPIM3

Håkon Alseth — Thu, 28 Sep 2023 12:21:13 GMT

Hi,

[quote user="Martin Sollie"]just like the radio uses power only when it needs to.[/quote]

Radio is always disabled after use, to achieve lowest possible current.

In order to achieve low power consumption, we recommend that you follow the description in the PS:

https://infocenter.nordicsemi.com/topic/ps_nrf52840/spim.html?cp=5_0_0_5_24_4#concept_twi_low_power

In addition to the above, as you've also pointed out, errata #195 is required to enter lowest possible sleep mode after using (and disabling) the peripheral.

Kind regards,

Håkon

RE: High power consumption when using SPIM3

Martin Sollie — Wed, 27 Sep 2023 15:08:25 GMT

Is the increased standby current of SPIM3 not related to the product anomaly then, but simply expected, even when using SPIM3 at low frequencies (<= 8 MHz)? In other words, should I expect to see approximately the same increase in current if the anomaly were to be fixed in a later revision of the nRF52840?

I would not have expected SPIM3 to draw so much current when not actively in use, just like the radio uses power only when it needs to. The SD card is used by a logging backend, but it can be a long time between each write. The increase in standby current consumption when using SPIM3 without manually suspending instead of SPIM2 is extreme.

The situation would be more understandable if the "stuck" high power consumption is the result of the anomaly also affecting idling between transfers, and not just a failure to properly disable the peripheral when un-initializing.

RE: High power consumption when using SPIM3

Håkon Alseth — Wed, 27 Sep 2023 14:21:30 GMT

Hi,

SPIM3 does draw more power when enabled compared to other (slower) SPIM peripherals.

The driver port, zephyr/drivers/spi/spi_nrfx_spim.c, does not automatically uninit the SPIM peripheral. This has to be done by the application at this time, using the call to "pm_device_action_run(my_spi_dev, PM_DEVICE_ACTION_SUSPEND);"

Kind regards,

Håkon