How to reduce the power consumption of the 9160‘s modem?

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Tue, 03 May 2022 08:42:54 GMT

[quote user="duxinglang"]Actually, what I want to know is how to use the modem without borrowing the UART to transmit commands or data.[/quote]

Again, UART is not used for communication between the application and the modem. Your application can send AT commands directly to the modem using the AT interface library, or you can e.g. make usage of the LTE link controller doing that for you.

If you would like to disable logging via UART, you can do that with an overlay.conf file, as illustrated here, or use a devicetree overlay to disable the peripheral itself.

Regards,

Markus

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Fri, 29 Apr 2022 03:35:53 GMT

Thank you for your reply. Actually, what I want to know is how to use the modem without borrowing the UART to transmit commands or data. As I have described before, in order to save power consumption, I need to put the UART into low-power mode, so that every time there is a change in the modem, the system will crash. Now that I've found a way to turn off CONFIG_AT_HOST_LIBRARY and CONFIG_UART_INTERRUPT_DRIVEN in prj.conf, it looks like I can eliminate the use of UART when transferring data between the application and modem. The result of the test was that after setting the UART to low power, there was no system crash.

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Thu, 28 Apr 2022 06:43:51 GMT

[quote user="duxinglang"]If no AT instructions are used, do these corresponding interface functions explain how to use them? [/quote]

The communication between the modem and application is always based on AT commands. You can find a full overview and documentation of all the commands available here.

[quote user="duxinglang"]I checked the specifications and found that many modem operations are realized by sending AT instructions, such as the modem networking function w_lte_lc_init().[/quote]

The above mentioned function is part of the LTE link controller library, which is one of many that we are offering to improve user experience. They are basically a wrapper for AT commands, but in the end, those libraries use AT commands as well for direct communication with the modem. One example could be the system mode settings, which is called within the lte_lc_init() function.

Regards,

Markus

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Wed, 27 Apr 2022 01:00:11 GMT

Thank you for your explanation! If as you say, an application does not need the AT instruction to communicate with the modem, what are the interface functions that the application can use? I checked the specifications and found that many modem operations are realized by sending AT instructions, such as the modem networking function w_lte_lc_init(). If no AT instructions are used, do these corresponding interface functions explain how to use them?

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Tue, 26 Apr 2022 11:24:08 GMT

[quote user="duxinglang"]So, does this mean that 9160 still needs a uart to communicate with the modem?[/quote]

The nRF9160 has two separate cores, an application and a modem core. The application and the modem communicate with each other via the modem library interface, as already mentioned. So, if the application core is in lower-power state but the modem core not, the current consumption can still be significant.

[quote user="duxinglang"]Why can't the application call the relevant functions to communicate with the modem directly instead of sending AT instructions through the uart? Does this mean that every time you use a modem, you have to use a uart, so you have at least 600uA power consumption? [/quote]

No. Basically, a UART peripheral is not needed for the application to send AT commands to the modem. But that implies that the application handles all necessary communication with the modem itself. If the application requires a certain extern user interface for handling AT commands, then a UART peripheral might be required.

Regards,

Markus

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Tue, 26 Apr 2022 11:15:49 GMT

So, does this mean that 9160 still needs a uart to communicate with the modem? Why can't the application call the relevant functions to communicate with the modem directly instead of sending AT instructions through the uart? Does this mean that every time you use a modem, you have to use a uart, so you have at least 600uA power consumption?

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Tue, 26 Apr 2022 11:04:09 GMT

Hello,

[quote user="duxinglang"]So it's log output using uart0, right? But when I test, I find that even though I have log output turned off (CONFIG_LOG= N), if I don't set UART0 to DEVICE_PM_LOW_POWER_STATE, it still has around 600uA power consumption, why? [/quote]

That depends as well on what your application is doing otherwise and which peripherals are enabled by default in your devicetree. Referring to the overlay-low-power.conf file of the Asset Tracker v2, which demonstrates how to disable logging over UART.

And of course, the power consumption is depended on the modem state as well. If it is enabled, but not in PSM/eDRX, the current consumption will not decrease.

[quote user="duxinglang"]This setting can only be operated after the modem is set and the AT instruction is sent to connect to the network, otherwise the device will restart. [/quote]

Yes, that makes sense! UART0 is required to forward the AT commands to the application, which then will forward them to the modem via the modem library interface. If UART0 is disabled or in low power state, this is not possible unless another UART peripheral is used instead.

Regards,

Markus

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Sun, 24 Apr 2022 02:22:39 GMT

In addition, I also found that even if UART0 is set to DEVICE_PM_LOW_POWER_STATE, it also has timing requirements. This setting can only be operated after the modem is set and the AT instruction is sent to connect to the network, otherwise the device will restart.

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Sun, 24 Apr 2022 02:02:52 GMT

So it's log output using uart0, right? But when I test, I find that even though I have log output turned off (CONFIG_LOG= N), if I don't set UART0 to DEVICE_PM_LOW_POWER_STATE, it still has around 600uA power consumption, why?

# Log
CONFIG_LOG=n
CONFIG_LOG_IMMEDIATE=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n
CONFIG_LOG_DEFAULT_LEVEL=4
CONFIG_LOG_MODE_OVERFLOW=y
CONFIG_LOG_BACKEND_RTT_MODE_DROP=y
CONFIG_LOG_BACKEND_SHOW_COLOR=n
CONFIG_LOG_BACKEND_FORMAT_TIMESTAMP=n

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Fri, 22 Apr 2022 11:05:10 GMT

[quote user="duxinglang"]Do you mean 9160 does not need to use UART0 to communicate with modem?[/quote]

Yes.

[quote user="duxinglang"] However, previous tests showed that I did receive some log output about the network from UART0 while connecting to the network.[/quote]

The log output you are receiving comes from the modem via the modem library interface and then is forwarded to the terminal via UART0.

Regards,

Markus

RE: How to reduce the power consumption of the 9160‘s modem?

duxinglang — Fri, 22 Apr 2022 08:15:33 GMT

Sorry, I didn't make it clear. I mean, I connected a sensor using Uart2.

Do you mean 9160 does not need to use UART0 to communicate with modem? However, previous tests showed that I did receive some log output about the network from UART0 while connecting to the network. The test results also show that if I set uART0 to low power, the power of the product does go down, which is very strange! The SDK version I am currently using is NCS1.2.0

RE: How to reduce the power consumption of the 9160‘s modem?

Albrecht Markus Schellenberger — Fri, 22 Apr 2022 08:08:51 GMT

Hello,

[quote user=""]My product design uses UART2 to communicate with a peripheral. [/quote]

I’m not quite sure if I fully have understood your setup yet.

[quote user=""]I know that 9160 communicates with the modem through the default UART0.[/quote]

The application core of the nRF9160 does not communicate with the modem via uart0. This is done via a shared memory area using the modem library, as described here. Do you run the application on a nRF9160 or another device, which communicates with the nRF9160 via uart0?

[quote user=""]In fact, the GPIO pin mapped to UART0 is not connected to any line, why do you need to set the low power state to reduce power consumption? [/quote]

The UART peripheral is powered by the HFCLK clock controller and not the peripheral itself. So if pins are assigned to uart0 doesn’t really matter, as long as the peripheral is enabled in the devicetree.

Regards,

Markus