RE: Using low-power VS non low-power mode peripherals

Vidar Berg — Tue, 13 Feb 2024 10:53:41 GMT

Hello,

The 'low-power-enable' property tells the Pin Control module to configure the peripheral pins as inputs with the input buffer disconnected when the sleep state is applied. This is to avoid leakage currents on from the IOs when the peripheral is suspended. However, it is often not necessary to suspended SPI and I2C buses.

[quote user=""]3. How much power exactly can I save? Are there any numbers available in the specification ?[/quote]

I recommend you to measure the current power consumption before starting to optimize.

[quote user=""]4. What are the disadvantages of using low power peripheral mode (for example using low power UART1 when comparing it with the default mode?[/quote]

The UART peripheral must be suspended while not in use to achieve low sleep currents, as it will keep the HF clock enabled otherwise. But please note that you cannot receive data while the peripheral suspended.

The low power mode mentioned in the pinctrl node is only used while the peripheral is suspended/disabled.

[quote user=""]5. How to enable the low power peripheral mode? Is simply having CONFIG_NRF_SW_LPUART=y and CONFIG_UART1_NRF_ASYNC_LOW_POWER=y enough?[/quote]

You need the REQ and RDY handsake signals to use the LP UART driver.

[quote user=""]6. From what I understand, using lpuart only makes sense if you have full control of both devices that use UART to communicate because you need to implement additional logic for REQ and RDY pins. Is that correct? I cant simply using LPUART if I want to communicate with the external GNSS that only uses RX/TX[/quote]

Yes, you are correct.

Best regards,

Vidar