[mbed] nRF51822 low-power operation (#670)

[BaN-Co]

Hello,

There is problem with current consumption in Bluetooth applications and current version of mbed SDK.
I'm using nRF51822-EK board for tests.
I created test project based on BLE_HeartRate example with last versions of libraries: mbed-src, nRF51822, BLE_API.

/* mbed Microcontroller Library
 * Copyright (c) 2006-2013 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "mbed.h"
#include "BLEDevice.h"
#include "HeartRateService.h"
#include "BatteryService.h"
#include "DeviceInformationService.h"

BLEDevice  ble;

const static char     DEVICE_NAME[]        = "Nordic_HRM";
static const uint16_t uuid16_list[]        = {GattService::UUID_HEART_RATE_SERVICE,
                                              GattService::UUID_BATTERY_SERVICE,
                                              GattService::UUID_DEVICE_INFORMATION_SERVICE};
static volatile bool  triggerSensorPolling = false;

void disconnectionCallback(Gap::Handle_t handle, Gap::DisconnectionReason_t reason)
{
    ble.startAdvertising(); // restart advertising
}

void periodicCallback(void)
{
    /* Note that the periodicCallback() executes in interrupt context, so it is safer to do
     * heavy-weight sensor polling from the main thread. */
    triggerSensorPolling = true;
}

int main(void)
{
    Ticker ticker;
    ticker.attach(periodicCallback, 1);

    ble.init();
    ble.onDisconnection(disconnectionCallback);

    /* Setup primary service. */
    uint8_t hrmCounter = 100;
    HeartRateService hrService(ble, hrmCounter, HeartRateService::LOCATION_FINGER);

    /* Setup auxiliary services. */
    BatteryService           battery(ble);
    DeviceInformationService deviceInfo(ble, "ARM", "Model1", "SN1", "hw-rev1", "fw-rev1", "soft-rev1");

    /* Setup advertising. */
    ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED | GapAdvertisingData::LE_GENERAL_DISCOVERABLE);
    ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_16BIT_SERVICE_IDS, (uint8_t *)uuid16_list, sizeof(uuid16_list));
    ble.accumulateAdvertisingPayload(GapAdvertisingData::GENERIC_HEART_RATE_SENSOR);
    ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LOCAL_NAME, (uint8_t *)DEVICE_NAME, sizeof(DEVICE_NAME));
    ble.setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
    ble.setAdvertisingInterval(1600); /* 1000ms; in multiples of 0.625ms. */
    ble.startAdvertising();

    while (true) {
        if (triggerSensorPolling) {
            triggerSensorPolling = false;

            /* Do blocking calls or whatever is necessary for sensor polling. */
            /* In our case, we simply update the dummy HRM measurement. */
            hrmCounter++;
            if (hrmCounter == 175) {
                hrmCounter = 100;
            }

            hrService.updateHeartRate(hrmCounter);
        } else {
            ble.waitForEvent();
        }
    }
}

And results is that in advertising state device consumes 5uA in low-power mode (ble.waitForEvent()) with small current spikes when device send advertising packets. But when I connect to the device the current consumption rise up to 1mA continuous consumption with small spikes when device receive/send packets. When disconnecting device once again start advertising and consumes 5uA in low-power mode.
My assumption is that when in connected state somewhere HFCLK Timer is used instead of low-power timer based on RTC1.
Can someone check it out?

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[BaN-Co]

It seems it's more related to the BLE_API library so I reposted it here:
mbedmicro/BLE_API#1
And closed this issue.

[BaN-Co]

Closed #670.