Can the LPUART be used without the 2 additional control lines?

[Kiran S.]

Hey Folks,

The new LPUART (doc here https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.0/nrf/drivers/uart_nrf_sw_lpuart.html) is supposed to address the issue of the UART consuming a few hundred microamps. It requires two additional control lines: REQ and RDY.

The custom board I'm building firmware for does not have these additional control lines. But all I need to do is issue a fire and forget command using the UART (or LPUART) and not worry about a response.

Given that two-way comms is not required, can the LPUART be used without the 2 control lines? If not, is another valid approach to just continue using the standard UART driver and shut down the peripheral directly without Zephyr's involvement?

Regards,

Kiran

[Kenneth]

It is UART RX that consume current consumption, while TX only consume power during transmission. So in your case you should be able to use any UART implementation you can find, simply don't start RX to achieve low power. If you use LPUART, then there is no need to use the additional control lines no, though since that driver have been made in specific to use the control lines to achieve low power, you may need to handle this pins in some way (e.g. leave them unconnected will cause REQ pin go high, thereby RX is not started).

Kenneth

[Anthony Yuan]

Hi Kiran,

I met the same issue on my custom board too.

Did you find a solution of the 2-wire UART current consumption?

Regards,

Anthony