Turn off UART on nrf52832

RE: Turn off UART on nrf52832

genis — Thu, 06 Apr 2017 08:24:22 GMT

I couldn't replicate the problem with a minimal example but I finally found out the solution. On the project I work in we add a timestamp to any message we log through the UART. And we calculate that timestamp in seconds using floating point operations. The issue was related to the one in devzone.nordicsemi.com/.../, as I didn't clear the FPU interrupt flags.

RE: Turn off UART on nrf52832

genis — Thu, 09 Feb 2017 14:53:08 GMT

Sure thing, I'll send some sample code but it'll take some time as some other stuff is more urgent. Thanks :)

RE: Turn off UART on nrf52832

Susheel Nuguru — Thu, 09 Feb 2017 14:49:43 GMT

UART should not take more than 55uA current, I would like to see this problem at my desk, so it would be nice if you can reproduce it and give me sample code to test. I could then assist you much faster.

RE: Turn off UART on nrf52832

genis — Thu, 09 Feb 2017 10:03:22 GMT

Hello Aryan, now I enable and disable the UART every single time I need to write something in it so I only do the __WFI() on the idle task. Still, I see the same behaviour. We're talking of about 700uA to 170uA when I completely disable any UART. Though I do not discard a mistake in the code, it looks like when the UART is disabled some hardware is still draining current. I'll try to make a simpler code sample to reproduce that. Also, the cpu is waken every 500ms by and also by the BLE hardware which advertises.

RE: Turn off UART on nrf52832

Susheel Nuguru — Tue, 07 Feb 2017 19:29:57 GMT

that depends on how much your system is sleeping which totally depends on your application. How much current difference are you observing?

RE: Turn off UART on nrf52832

genis — Tue, 07 Feb 2017 16:53:03 GMT

Sorry for the late response. That actually disables and reenables the UART but I still see a lot of current consumption that I don't see if I totally disable the UART. I use the UART through app_uart_fifo.c library.

RE: Turn off UART on nrf52832

Susheel Nuguru — Mon, 30 Jan 2017 09:19:20 GMT

You are mixing up using UART driver and accessing registers directly. This will cause the unpredictable behavior you are seeing now. I recommend you to uninit UART and init again using the driver. Since you said that it will 99% in idle the overhead for uninit and init everytime it wakes up is negligible.

/* FreeRTOS application idle hook */
void vApplicationIdleHook(void) {   
    // Disable UART transmission and reception
    bool uart_disabled = false;
    if (!nrf_drv_uart_tx_in_progress()) {
        nrf_drv_uart_uninit(uart_instance);
        uart_disabled = true;
    }

    __WFI();

    if (uart_disabled) {
        nrf_drv_uart_init(xxx);
   }    
}

I think the reason that writing directly to ENABLE not working is because the pins are still configured to be connected to UART . Anyways, let the driver take care of this.