SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

RE: SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

Joris Roussel — Sat, 10 Mar 2018 11:07:59 GMT

Happy for having raised a common issue :-)

RE: SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

Tarun — Sat, 10 Mar 2018 09:44:17 GMT

Thanks Joris.

This worked for me as well 🙂

RE: SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

Joris Roussel — Thu, 08 Mar 2018 16:33:15 GMT

Hi Kenneth,

That makes sense. Thanks for handling this case

Best regards,

RE: SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

Kenneth — Thu, 08 Mar 2018 16:24:38 GMT

Seems you have identified the issue then, likely the MISO pin is pulled low by the slave spi in this case, thereby there is a leakage current through the internal pull-up resistor on-chip. The reason the internal pull-up have been introduced on newer SDK is to make sure that the pin doesn't float, but do have a defined level when not in use. Floating input pins can create a range of excessive current consumption issues over time, so having a pull up (or pull Down is likely better in this case) when not in use is a good idea in general.

RE: SPI very high power consumption with SDK14.2.0 but low with SDK12.3.0

Joris Roussel — Thu, 08 Mar 2018 09:07:20 GMT

Hi all,

The higher power consumption comes from the pullup on MISO pin. On SDK 12.3.0, the pin is always configured with no pullup. On SDK 14.2.0, the pullup is configurable (NRF_SPI_DRV_MISO_PULLUP_CFG, which was set to 1 in my sdk_config). I set it to 0, power consumption is now below 10µA.

Why this pullup is drawing so much current ?

Best regards,

Joris