LPUART req pin low when expected high

RE: LPUART req pin low when expected high

Hung Bui — Thu, 23 Oct 2025 12:34:55 GMT

Hi Roman,
Sorry I thought that you didn't have the lpuart: Empty receiver state:4 error with the DK.

I think it's a known issue:
RE: Bluetooth HCI lpuart issue - nRF9160 + nRF52840

But do you have other error after the <err> lpuart: Empty receiver state:4 ?
We need to see if you have the same problem or not.

RE: LPUART req pin low when expected high

Roman Veselskyi — Thu, 23 Oct 2025 09:12:49 GMT

Hello Hung Bui ,

I am using the nRF9160DK together with the samples from SDK with no changes, this info was mentioned on request. I am expecting the configuration must be correct at least from the Nordic provided samples, did you try it on your side with DK?

RE: LPUART req pin low when expected high

Hung Bui — Wed, 22 Oct 2025 10:46:03 GMT

Hi Roman,
My suggestion is to try testing with only one side first. You can manually pull the LP pin low and high to test. Have you tested with the lpuart sample ?
Please double check if the req and rdy pins are configured correctly.

RE: LPUART req pin low when expected high

Roman Veselskyi — Wed, 22 Oct 2025 09:41:24 GMT

Hi,

Thanks for the reply, but what about first two errors?

[00:00:00.311,279] <wrn> lpuart: req pin low when expected high
[00:00:00.311,401] <err> lpuart: Empty receiver state:4

RE: LPUART req pin low when expected high

Hung Bui — Tue, 21 Oct 2025 10:41:22 GMT

Hi Roman,
What you reported could be not related to LPUART. Can you take a look here?

bt_gatt: Unable to import the key for AES CMAC -141
Amanda provided a link to the fix.