How do I reduce power consumption on the UART interface

RE: How do I reduce power consumption on the UART interface

Simon — Wed, 23 Jun 2021 13:28:31 GMT

Have you solved the issue? If not could you upload your application as a zipped file and I can take a look at it.

Best regards,

Simon

RE: How do I reduce power consumption on the UART interface

duxinglang — Fri, 18 Jun 2021 03:07:39 GMT

In fact, I only set the value of one variable in the timer callback function and nothing more. Later, I tried various operations and thought it was a system anomaly caused by the thread for some reason, because I found that everything was fine when the timer was sleeping the UART, but there was a problem waiting for me to wake the uart up again.

RE: How do I reduce power consumption on the UART interface

Simon — Thu, 17 Jun 2021 10:04:47 GMT

I would not recommend you to do much processing in timer interrupts. See this answer for more details: https://devzone.nordicsemi.com/support-private/support/271094#permalink=669503.

Instead you should offload it to a work queue (like done here) or offload it to another thread usin k_sem_give()/k_sem_take().

RE: How do I reduce power consumption on the UART interface

duxinglang — Thu, 17 Jun 2021 05:41:59 GMT

Now, i can confirm that it wasn't the log that caused the crash, it was the timer I used to make the UART sleep automatically, but strangely enough, if I hadn't set sleep in the timer timeout callback, this problem wouldn't have occurred, which is very strange!

RE: How do I reduce power consumption on the UART interface

duxinglang — Wed, 16 Jun 2021 02:58:40 GMT

Maybe it has something to do with Log sending, because after I shut down all the logs, this problem doesn't seem to appear again, but I found a new problem, that is, if I use the timer to automatically hibernate the UART, and then press the button to wake up the UART, it will still enter the crash state, why?

RE: How do I reduce power consumption on the UART interface

duxinglang — Wed, 16 Jun 2021 02:56:13 GMT

Yes, I did send some log information to the PC, not via uart, but set up rtt to use swd interface.

RE: How do I reduce power consumption on the UART interface

Simon — Fri, 11 Jun 2021 16:44:01 GMT

[quote user="duxinglang"]I executed several keystrokes[/quote]

What do you mean by this? Are you trying to send data from the computer to the device over UART while it's disabled?

RE: How do I reduce power consumption on the UART interface

duxinglang — Wed, 09 Jun 2021 10:42:27 GMT

Thanks for your reply!

I tried to call a function to let the uart enter sleep and wake up to reduce the power consumption, but I found that when my uart entered the state of low power consumption, I executed several keystrokes and the system crashed. Why?

This is my code:

void uart_sleep_out(void)
{
#ifdef CONFIG_DEVICE_POWER_MANAGEMENT
	int err;

	err = device_set_power_state(uart_ble, DEVICE_PM_ACTIVE_STATE, NULL, NULL);
	if(err)
		LOG_INF("uart set active fail!\n");
	else
		LOG_INF("uart set active success!\n");
#endif
}

void uart_sleep_in(void)
{
#ifdef CONFIG_DEVICE_POWER_MANAGEMENT
	int err;

	err = device_set_power_state(uart_ble, DEVICE_PM_SUSPEND_STATE, NULL, NULL);
	if(err)
		LOG_INF("uart set low power fail!\n");
	else
		LOG_INF("uart set low power success!\n");
#endif
}

RE: How do I reduce power consumption on the UART interface

Simon — Tue, 08 Jun 2021 09:45:42 GMT

The link provided by Adeel is a useful one, take a look at that. The reason UART uses that much power is because the RX pin is constantly on (don't know when the connected device will send data), which needs the HF-clock. The HF-clock uses about 500uA-1mA. If you don't need the RX pin (e.g. only using uart for logging) you can simply disable it like explained here: https://devzone.nordicsemi.com/f/nordic-q-a/64532/nrf52840-peripheral_uart-low-power-ncs-1-3-0/279199#279199

Another option is to use the low power uart driver, which will make the slave send a signal to a pin before transmitting and RX can be turned off while not in use. Check out the Low Power UART sample, which demonstrate how to use this driver.

Best regards,

Simon

RE: How do I reduce power consumption on the UART interface

Adeel — Mon, 07 Jun 2021 11:32:59 GMT

Hi,

This thread could help : https://devzone.nordicsemi.com/f/nordic-q-a/69534/thingy91-power-consumption

You can turn off and turn on the uart during run time and conserve power.

Regards,

Adeel.