GPIO and UART with low power consumption?

RE: GPIO and UART with low power consumption?

Hung Bui — Wed, 20 Dec 2017 09:47:24 GMT

300uA sounds correct as the UART peripheral requires HFCLK and if you run HFCLK with the 64MHz crystal current consumption will be ~250uA. If you let UART running with RX task the 250+uA will constantly consumed. You can think of other way to disable RX when not needed, for example software flow control, or use an extra GPIO pin to signal it.

RE: GPIO and UART with low power consumption?

Nate — Tue, 19 Dec 2017 14:39:57 GMT

That's the CPU without EasyDMA.

RE: GPIO and UART with low power consumption?

Hung Bui — Tue, 19 Dec 2017 11:48:32 GMT

300ua is when you use EasyDMA or when you use CPU ? Depends on how often you do UART communication it could get to 300uA with the CPU. With EasyDMA it actually should be higher.

RE: GPIO and UART with low power consumption?

Nate — Mon, 18 Dec 2017 19:23:30 GMT

I saw commits that I thought said it took more for EasyDMA, In order to get the currents down I went to the driver level and implemented custom enabling and disabling. When on I couldn't get it below 300ua

RE: GPIO and UART with low power consumption?

Hung Bui — Tue, 12 Dec 2017 12:16:32 GMT

@Nate: Have you looked at the spec on current consumption for EasyDMA ? It's actually lower power consumption to use the CPU to handle UART shortly.

RE: GPIO and UART with low power consumption?

Nate — Tue, 05 Dec 2017 21:04:16 GMT

Did you figure this out? I am running into the same issues with power and the uart and my numbers are almost the same as yours as far as power with the uart enabled and disabled

RE: GPIO and UART with low power consumption?

Hung Bui — Mon, 17 Jul 2017 12:16:14 GMT

Please have a look at the nRF52 product spec at chapter 10 and chapter 35.2

To disable EasyDMA on the UART driver, turn off UART0_CONFIG_USE_EASY_DMA in sdk_config.h as told here.

RE: GPIO and UART with low power consumption?

HelloWorld — Fri, 14 Jul 2017 09:16:29 GMT

what does EASYDMA do exactly? and where can i disable it?

RE: GPIO and UART with low power consumption?

Hung Bui — Wed, 12 Jul 2017 10:47:52 GMT

Hi again,

Another tip is to disable EASYDMA , it can consume a lot of power compare to letting the CPU handle the incoming data.

RE: GPIO and UART with low power consumption?

Hung Bui — Tue, 11 Jul 2017 10:55:02 GMT

Hi,

If you have a look at app_uart_init() which is called by APP_UART_FIFO_INIT, you can find that nrf_drv_uart_rx_enable() is called by default.

With RX enabled the UART will keep the 16Mhz oscillator running and the regulators in addition.

Have you tried to call nrf_drv_uart_rx_disable() after you call APP_UART_FIFO_INIT to put the UART in idle mode ?

What exactly inside the gpioi_init() ? Do you use GPIOTE pin interrupt ?