NRF52832 UART Power consumption

[AntonHellbe]

Hi,

I just wanna start off by saying I know there a lot of similar posts to this one here on the dev zone, but my problem with them is that none of them (from what I've seen) give a good answer what to do in order to reduce the power consumption of the UART peripheral when it's active.

My observation is that as soon as I activate the UART (data is constantly sent when activating the UART) the current consumption averages around 2.4mA. I need to be able to reduce this as much as possible.

One of the topics I found was this one:
https://devzone.nordicsemi.com/f/nordic-q-a/28439/gpio-and-uart-with-low-power-consumption

however the solutions presented in that topic only reduces current consumption when the UART is idle.

Another topic that is similar to mine, but not answered:

devzone.nordicsemi.com/.../how-to-configure-uart-with-low-power

Furthermore, I found the low power examples for nRF51:

https://github.com/NordicPlayground/nrf51-UART-examples/tree/master/ble_app_uart_low_power

Are these valid for nRF52 as well? or are there some equivalent examples for nRF52?

SDK: v15.0

HW: nRF52832 PCA10040

Br,
Anton

[Jørgen Holmefjord]

Hi,

Are you using the UARTE peripheral (UART with EasyDMA enabled)? If you are, you will most likely not be able to reduce the run current of the UART very much. Are you using the UART driver, or APP_UART library? If you could share your code/project, I can help give you some advice.

Best regards,
Jørgen

[Jørgen Holmefjord]

Do you have UART0_CONFIG_USE_EASY_DMA  set to 1 in your sdk_config file?

[AntonHellbe]

No, I cannot find that define in my sdk_config.

[Jørgen Holmefjord]

I still think your application are using UARTE peripheral, I get ~2.1 mA average with UARTE and ~0.5 mA with UART. Try excluding nrfx_uarte.c from your project, and make sure you set the following configs in sdk_config.h:

#define UART_EASY_DMA_SUPPORT 0
#define UART_LEGACY_SUPPORT 1
#define UART0_CONFIG_USE_EASY_DMA 0

[AntonHellbe]

I made the changes you suggested.

However now I receive the APP_UART_COMMUNICATION_ERROR event during transmission.

Are there any differences in how I should use app_uart_put / get when using UART without DMA?

[Jørgen Holmefjord]

APP_UART_COMMUNICATION_ERROR is typically caused by hardware issues. Did you use the same pins for UART and run it on the nRF52 DK? Can you check which error you get with the event?

Usage of the library should not differ with use of EasyDMA or not.