LPUART nRF9160 - nRF52840

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Wed, 21 Jul 2021 10:15:01 GMT

Hello again Michal,

I have to correct myself here:

[quote user="Markus Schellenberger"]Hence, its purpose is not to demonstrate energy efficiency. If that is the main focus, you probably wouldn’t use the nRF9160 as a stand-alone modem only. But anyway, the LP UART is of course supposed to work regardless application.[/quote]

The Serial LTE modem application is of course something we are intending that our customers consider if they would like to use the nRF91 as a stand-alone modem only.

And as I already mentioned, we are working on a solution to make the LP UART more stable as we speak. Additionally, we will look into adding native support for it to the Serial LTE Modem application.

My very apologies for the confusion!

Regards,

Markus

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Tue, 20 Jul 2021 13:09:44 GMT

Thanks a lot for the feedback, Michal!

Regards,

Markus

RE: LPUART nRF9160 - nRF52840

Michal Mühlpachr — Tue, 20 Jul 2021 12:14:58 GMT

SML has #XSLEEP who cares of various sleep modes, LPUART would be nice to handle clock/UART sleeping in automated way. We use BLE in our device, so we need additional nRF52840 where whole application logic is implemented and nRF9160 servers just as modem. Because nRF9160 in sleep mode draws just around 7uA with SLM it is still more then appropriate for low power battery operated device.

CONFIG_ZERO_LATENCY_IRQS=n is default for SLM

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Tue, 20 Jul 2021 10:06:24 GMT

Hello Michal,

[quote user="michalm"]What do you think about LPUART native support in SLM ?[/quote]

I’m not sure if this is the intention of the Serial LTE modem application. As described in the application guideline, "The Serial LTE Modem (SLM) application demonstrates how to use the nRF9160 as a stand-alone LTE modem that can be controlled by AT commands." Hence, its purpose is not to demonstrate energy efficiency. If that is the main focus, you probably wouldn’t use the nRF9160 as a stand-alone modem only. But anyway, the LP UART is of course supposed to work regardless application.

I haven’t tested this myself yet, but what you could try in the meantime is to disable Zero-latency interrupt extension by setting:

CONFIG_ZERO_LATENCY_IRQS=n

in your prj.conf. This should give better performance to the module.

Regards,

Markus

RE: LPUART nRF9160 - nRF52840

Michal Mühlpachr — Fri, 16 Jul 2021 17:34:31 GMT

Hi Markus,

thank you for info and confirmation.

What do you think about LPUART native support in SLM ?

Ragers,

Michal

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Tue, 13 Jul 2021 11:14:24 GMT

Thanks for the feedback, Michal!

I had to check this internally. It seems to be a known issue and we are working on a more stable solution for the LP UART as we speak. It will be released soon.

Regards,

Markus

RE: LPUART nRF9160 - nRF52840

Michal Mühlpachr — Mon, 12 Jul 2021 15:36:37 GMT

Yes, we have added LPUART configuration in .dts, we use our board definitions for both nRF9160 and nRF52840 (no overlay needed). Related nRF9160 part:

&gpiote {
	status = "okay";
	interrupts = <49 NRF_DEFAULT_IRQ_PRIORITY>;
};

&gpio0 {
	status = "okay";
};

&uart0 {
	compatible = "nordic,nrf-uarte";
	current-speed = <115200>;
	status = "okay";
	tx-pin = <21>;
	rx-pin = <22>;
	/delete-property/ hw-flow-control;
	/delete-property/ rts-pin;
	/delete-property/ cts-pin;
	lpuart: nrf-sw-lpuart {
		compatible = "nordic,nrf-sw-lpuart";
		status = "okay";
		label = "LPUART";
		req-pin = <23>;
		rdy-pin = <24>;
	};
};

nRF9160 is interconnected with nRF52840 by 4 wires and nRF52840 uses similar .dts for LPUART and device_get_binding("LPUART"). Both nRF9160 and nRF52840 are on our custom HW. Our custom HW has different pin wiring than nRF9160 DK, so we can use UART0.

CONFIG_SLM_CONNECT_LPUART config option is also our patch, you do not need to pay attention to that.

Core issue is, that 4wire LPUART is not stable, 2wire UART works fine with same code, only related LPUART .dts and device_get_binding("LPUART") have changed.

Both nRF9160 and nRF52840 firmware projects are based on released NCS v1.6.0.

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Mon, 12 Jul 2021 12:47:08 GMT

Hello Michal,

[quote user="michalm"]LPUART is not supported in SLM in NCS v1.6.0 unfortunately.[/quote]

I haven’t tried this myself with the Serial LTE modem application, but I’m not quite sure if this actually is the case. The Low Power UART is a module that should be possible to configure individually.

As the Low Power UART example shows, the module itself has to be added to a UART peripheral using an overlay file.

[quote user="michalm"]We made some SLM code tweaks (e.g. uart_dev = device_get_binding("LPUART") in slm_at_host.c).[/quote]

When connection the nRF9160 with an external MCU, the UART2 is designated to be used. Hence, the Low Power UART module has to be added to UART2 in the overlay file.

lpuart: nrf-sw-lpuart {
compatible = "nordic,nrf-sw-lpuart";
status = "okay";
label = "LPUART";
req-pin = <xy>;
rdy-pin = <xy>;
};

This is not done be default in the Serial LTE modem application, hence device binding will fail.

Regarding the configuration option CONFIG_SLM_CONNECT_LPUART, mentioned in this ticket: This is nothing I’m aware of, neither can I find it in the application configuration description.

Regards,

Markus

RE: LPUART nRF9160 - nRF52840

Michal Mühlpachr — Mon, 12 Jul 2021 09:24:05 GMT

UART .dts definitions are described in devzone.nordicsemi.com/.../lpuart-nrf9160---nrf52840

RE: LPUART nRF9160 - nRF52840

Michal Mühlpachr — Mon, 12 Jul 2021 09:22:20 GMT

LPUART is not supported in SLM in NCS v1.6.0 unfortunately.
We made some SLM code tweaks (e.g. uart_dev = device_get_binding("LPUART") in slm_at_host.c).
We would appreciate LPUART support in SLM for reasons described above.

Simple test case with periodic sending AT+CFUN? every second transaction fails (no response returned from nRF9160)

Thanks and regards, Michal

RE: LPUART nRF9160 - nRF52840

Albrecht Markus Schellenberger — Mon, 12 Jul 2021 09:06:04 GMT

Hello Michal,

thanks a lot for your feedback!

[quote user=""]We appreciate the addition of the native support for LPUART in SLM (without need to modify sources - just using prj.conf option).[/quote]

I have to admit that I’m not sure if I can follow you here. The Changelog for NCS v1.6.0 does not mention anything about it. Can you elaborate?

[quote user=""]With ncs v1.6.0 every second AT transaction fails.[/quote]

Would you mind sending me an application log that shows the issue you are facing? I might want to check and report this internally.

Thanks and regards,

Markus