nrf51822 never sleeps with Serial declared

Questions » nrf51822 never sleeps with Serial declared

7 years, 6 months ago.

Hi,

I have Seeed Tiny_BLE board with power monitoring circuit.

Q1) How to turn off Serial port correctly?
Q2) When compiler finds Serial initialization (see code below) it never put device to sleep (current consumtion about 1mA) . Even if this part of code will not be called. If I comment pc = new Serial(UART_TX, UART_RX); current cosumption is ok (10-20uA). So the question: is it possible to use sleep mode together with Serial port object?

include the mbed library with this snippet

#include "mbed.h"
#include "BLE.h"

#define LED_BLUE    p23
#define BUTTON_PIN  p17

#define UART_TX     p9
#define UART_RX     p11

DigitalOut blue(LED_BLUE);
Serial *pc  = NULL;

BLE  ble;
volatile bool bleIsConnected = false;
InterruptIn button(BUTTON_PIN); 

void startUart()
{
    pc = new Serial(UART_TX, UART_RX);
} 
void detect(void)
{
    blue = !blue;
    if (pc!=NULL) 
        startUart();
    else
        pc = NULL;
}

int main(void)
{
    blue  = 1;
    button.fall(detect);
    ble.init();
    ble.setAdvertisingInterval(800); /* 100ms; in multiples of 0.625ms. */
    ble.gap().startAdvertising();
    while (true) {        ble.waitForEvent();  }
}

1 Answer

7 years, 6 months ago.

Hi Klym,

It is not possible to put the serial to sleep with mbed primitives. This is a known issue (see here) which has to be resolved.

You can directly disable it as a workaround:

// include definitions
#include "device.h"

// disable the UART: 
((NRF_UART_Type *) UART0)->ENABLE = (UART_ENABLE_ENABLE_Disabled<< UART_ENABLE_ENABLE_Pos);


// enable the UART: 
((NRF_UART_Type *) UART0)->ENABLE = (UART_ENABLE_ENABLE_Enabled << UART_ENABLE_ENABLE_Pos);

Accepted Answer

Vincent,

thanks for info. Seems this code is working but there is one condition: UART should finish to transmit all data before 'Disable'. Otherwise, for example if you have pc.printf("something"); disbaleUart(); UART will not work after wake up.

What I can also find, possible it's the best way:

//to disable UART
   NRF_UART0->TASKS_SUSPEND=1;  
//to re-enable UART
     NRF_UART0->ENABLE        = UART_ENABLE_ENABLE_Enabled << UART_ENABLE_ENABLE_Pos;
     NRF_UART0->TASKS_STARTTX = 1;
     NRF_UART0->TASKS_STARTRX = 1;

posted by Klym T 24 Nov 2016

Klym T

Important changes to forums and questions

7 years, 6 months ago.