Current Consumption when using timer and scheduler alongwith nrf_pwr_mgmt_run().

[Rajat]

Hi Everyone,

I am using the following peripherals in my project

2 UARTE.

2 ADC 

1 TWI

BLE

GPIOTE interrupt for 2 buttons

TWI and ADC and BLE and GPIOTE are not consuming more current when there are no events (when its in sleep mode, current is around 240uA)

However , when i initialise the 2 UART and also uninit both of them , the current doesn't come below 1.1mA , Is it Normal?

If not , how can i set up the UART part to use 2 UARTEs without consuming much current in the sleep mode , when there are no events occuring.

I have a custom PCB using nrf52840 , SDK 15.0 And Segger Embedded Studio IDE.

[Einar Thorsrud]

Hi,

The UART peripherals will consume current as long as it is enabled (by itself and because it needs other resources such as the HF clock), but it should not cause high current consumption after it has been disabled. Can you share your UART code with us, particularly how it is disabled before going to sleep?

[Rajat]

https://devzone.nordicsemi.com/f/nordic-q-a/25173/nrf52840-uart1-not-working-in-sdk-14

I am using the exact same procedure to initalise the UARTs.

To Uninit , i am using , 

---

nrf_serial_uninit(&serial1_uarte);

nrf_serial_uninit(&serial0_uarte);

---

However , to initialise the UART , i am using only the event handler , and not the sleep handler , because UART was disabled after 3 minutes or so which i don't need .

---

NRF_SERIAL_CONFIG_DEF (serial0_config, NRF_SERIAL_MODE_DMA, &serial0_queues,
&serial0_buffs, event_handler_serial0, NULL);

NRF_SERIAL_CONFIG_DEF (serial1_config, NRF_SERIAL_MODE_DMA, &serial1_queues,
&serial1_buffs, event_handler_serial1, NULL);

---

[Rajat]

But i am not able to reinit the UART

[Einar Thorsrud]

Hi,

The approach shown by Stian is a sensible workaround. It uses a hidden register to reset the peripheral. I tested the approach on my side, and I am able to get current consumption down and to reconfigure the UARTE peripherals properly. This modified code from the Serial Port Library Example with two UARTEs example for SDK 15.2 demonstrates the fix:

Fullscreen 85300.main.c Download

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 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
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 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>

#include "nrf.h"
#include "nrf_drv_clock.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_serial.h"
#include "app_timer.h"


#include "app_error.h"
#include "app_util.h"
#include "boards.h"

/** @file
 * @defgroup nrf_serial_uartes_example main.c
 * @{
 * @ingroup nrf_serial_uartes_example
 * @brief Example of @ref nrf_serial usage. Loopback example using two UARTE peripherals.
 *        Please short Arduino SCL and SDA GPIOs to start transmission.
 *
 */

#define OP_QUEUES_SIZE          3
#define APP_TIMER_PRESCALER     NRF_SERIAL_APP_TIMER_PRESCALER

static void sleep_handler(void)
{
    __WFE();
    __SEV();
    __WFE();
}

NRF_SERIAL_DRV_UART_CONFIG_DEF(m_uarte0_drv_config,
                      RX_PIN_NUMBER, ARDUINO_SCL_PIN,
                      RTS_PIN_NUMBER, CTS_PIN_NUMBER,
                      NRF_UART_HWFC_DISABLED, NRF_UART_PARITY_EXCLUDED,
                      NRF_UART_BAUDRATE_115200,
                      UART_DEFAULT_CONFIG_IRQ_PRIORITY);

NRF_SERIAL_DRV_UART_CONFIG_DEF(m_uarte1_drv_config,
                      ARDUINO_SDA_PIN, TX_PIN_NUMBER,
                      RTS_PIN_NUMBER, CTS_PIN_NUMBER,
                      NRF_UART_HWFC_DISABLED, NRF_UART_PARITY_EXCLUDED,
                      NRF_UART_BAUDRATE_115200,
                      UART_DEFAULT_CONFIG_IRQ_PRIORITY);


#define SERIAL_FIFO_TX_SIZE 32
#define SERIAL_FIFO_RX_SIZE 32

NRF_SERIAL_QUEUES_DEF(serial0_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);
NRF_SERIAL_QUEUES_DEF(serial1_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);


#define SERIAL_BUFF_TX_SIZE 1
#define SERIAL_BUFF_RX_SIZE 1

NRF_SERIAL_BUFFERS_DEF(serial0_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);
NRF_SERIAL_BUFFERS_DEF(serial1_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);


NRF_SERIAL_CONFIG_DEF(serial0_config, NRF_SERIAL_MODE_DMA,
                      &serial0_queues, &serial0_buffs, NULL, sleep_handler);
NRF_SERIAL_CONFIG_DEF(serial1_config, NRF_SERIAL_MODE_DMA,
                      &serial1_queues, &serial1_buffs, NULL, sleep_handler);


NRF_SERIAL_UART_DEF(serial0_uarte, 0);
NRF_SERIAL_UART_DEF(serial1_uarte, 1);


static void uart_test(int test_num)
{
    ret_code_t ret;

    ret = nrf_serial_init(&serial0_uarte, &m_uarte0_drv_config, &serial0_config);
    APP_ERROR_CHECK(ret);

    ret = nrf_serial_init(&serial1_uarte, &m_uarte1_drv_config, &serial1_config);
    APP_ERROR_CHECK(ret);

    static char tx_message[40];
    snprintf(tx_message, sizeof(tx_message), "Hello nrf_serial! Test %d\n\r", test_num);

    ret = nrf_serial_write(&serial1_uarte,
                           tx_message,
                           strlen(tx_message),
                           NULL,
                           NRF_SERIAL_MAX_TIMEOUT);

    (void)nrf_serial_flush(&serial1_uarte, 0);

    int i = 0;

    while (true)
    {
        if(++i > 2) break; // break out after 10 timeouts (seconds)

        char c;
        ret = nrf_serial_read(&serial0_uarte, &c, sizeof(c), NULL, 1000);
        if (ret != NRF_SUCCESS)
        {
            continue;
        }
        (void)nrf_serial_write(&serial0_uarte, &c, sizeof(c), NULL, 0);
        (void)nrf_serial_flush(&serial0_uarte, 0);

        ret = nrf_serial_read(&serial1_uarte, &c, sizeof(c), NULL, 1000);
        if (ret != NRF_SUCCESS)
        {
            continue;
        }
        (void)nrf_serial_write(&serial1_uarte, &c, sizeof(c), NULL, 0);
        (void)nrf_serial_flush(&serial1_uarte, 0);
    }

    // Disable UART to reduce current consumption
    nrf_serial_uninit(&serial0_uarte);
    nrf_serial_uninit(&serial1_uarte);

    // Workaround by disabling the UART peripherals
    *(volatile uint32_t *)0x40002FFC = 0;   // Power down UARTE0
    *(volatile uint32_t *)0x40002FFC;       //
    *(volatile uint32_t *)0x40002FFC = 1;   // Power on UARTE0 so it is ready for next time

    *(volatile uint32_t *)0x40028FFC = 0;   // Power down UARTE1
    *(volatile uint32_t *)0x40028FFC;       //
    *(volatile uint32_t *)0x40028FFC = 1;   // Power on UARTE1 so it is ready for next time
}


int main(void)
{
    ret_code_t ret;

    ret = nrf_drv_clock_init();
    APP_ERROR_CHECK(ret);

    nrf_drv_clock_lfclk_request(NULL);
    ret = app_timer_init();
    APP_ERROR_CHECK(ret);

    uart_test(0);
    uart_test(1);

    // Enter low power mode
    while (true)
    {
        __SEV();
        __WFE();
        __WFE();
    }
}

/** @} */

The terminal printout shows that the UART's work after the have been reinitialized:

Hello nrf_serial! Test 0
Hello nrf_serial! Test 1

[Rajat]

I could get the low current by disabling the UARTE0 , but not for UARTE1. 

Don't you think , the address to disable UARTE0 and UARTE1 should be different?

[Einar Thorsrud]

The addresses for disabling UARTE0 and UARTE1 are different (0x40002FFC and 0x40028FFC). These registers are undocumented as they should not normally be used, but are needed as a workaround in this case.

Please refer to the code snippet in my previous answer for a full example that demonstrates how you can use both in low power mode. To extract just the main point you should use this code (I include the call to  nrf_serial_uninit() for completeness):

    // Disable UARTs to reduce current consumption
    nrf_serial_uninit(&serial0_uarte);
    nrf_serial_uninit(&serial1_uarte);

    // Workaround current consumption issue by power cycling the UART peripherals
    *(volatile uint32_t *)0x40002FFC = 0;   // Power down UARTE0
    *(volatile uint32_t *)0x40002FFC;       //
    *(volatile uint32_t *)0x40002FFC = 1;   // Power on UARTE0 so it is ready for next time

    *(volatile uint32_t *)0x40028FFC = 0;   // Power down UARTE1
    *(volatile uint32_t *)0x40028FFC;       //
    *(volatile uint32_t *)0x40028FFC = 1;   // Power on UARTE1 so it is ready for next time

[Rajat]

Thanks , It works :)