Demonstration of the GAP profile. It shows advertising, scanning and connecting. The demo will cycle through several modes and print over the serial connection information about current activity.

GAP - Advertising, Scanning, Connecting

Demonstration of GAP API usage. It shows advertising, scanning and connecting. The demo will cycle through several modes and print over the serial connection information about current activity.

Running the application

Requirements

The sample application can be seen on any BLE scanner on a smartphone. If you don't have a scanner on your phone, please install :

- nRF Master Control Panel for Android.

- LightBlue for iPhone.

Information about activity is printed over the serial connection - please have a client open. You may use:

- Tera Term

Hardware requirements are in the main readme.

Building instructions

Building instructions for all samples are in the main readme.

source/main.cpp

Committer:
mbed_official
Date:
4 months ago
Revision:
20:d2c272f79611
Parent:
16:4dd4ecbc8efb

File content as of revision 20:d2c272f79611:

/* mbed Microcontroller Library
 * Copyright (c) 2006-2018 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 <events/mbed_events.h>
#include <mbed.h>
#include "ble/BLE.h"
#include "gap/Gap.h"
#include "gap/AdvertisingDataParser.h"
#include "pretty_printer.h"

/** This example demonstrates all the basic setup required
 *  to advertise, scan and connect to other devices.
 *
 *  It contains a single class that performs both scans and advertisements.
 *
 *  The demonstrations happens in sequence, after each "mode" ends
 *  the demo jumps to the next mode to continue. There are several modes
 *  that show scanning and several showing advertising. These are configured
 *  according to the two arrays containing parameters. During scanning
 *  a connection will be made to a connectable device upon its discovery.
 */

events::EventQueue event_queue;

/* Duration of each mode in milliseconds */
static const size_t MODE_DURATION_MS      = 6000;

/* Time between each mode in milliseconds */
static const size_t TIME_BETWEEN_MODES_MS = 2000;

/* how long to wait before disconnecting in milliseconds */
static const size_t CONNECTION_DURATION   = 3000;

/* how many advertising sets we want to crate at once */
static const uint8_t ADV_SET_NUMBER       = 2;

static const uint16_t MAX_ADVERTISING_PAYLOAD_SIZE = 1000;

typedef struct {
    ble::advertising_type_t type;
    ble::adv_interval_t min_interval;
    ble::adv_interval_t max_interval;
} DemoAdvParams_t;

typedef struct {
    ble::scan_interval_t interval;
    ble::scan_window_t   window;
    ble::scan_duration_t duration;
    bool active;
} DemoScanParam_t;

/** the entries in this array are used to configure our advertising
 *  parameters for each of the modes we use in our demo */
static const DemoAdvParams_t advertising_params[] = {
/*    advertising type                                   | min interval - 0.625us  | max interval - 0.625us   */
    { ble::advertising_type_t::CONNECTABLE_UNDIRECTED,      ble::adv_interval_t(40), ble::adv_interval_t(80)  },
    { ble::advertising_type_t::SCANNABLE_UNDIRECTED,       ble::adv_interval_t(100), ble::adv_interval_t(200) },
    { ble::advertising_type_t::NON_CONNECTABLE_UNDIRECTED, ble::adv_interval_t(100), ble::adv_interval_t(200) }
};

/* when we cycle through all our advertising modes we will move to scanning modes */

/** the entries in this array are used to configure our scanning
 *  parameters for each of the modes we use in our demo */
static const DemoScanParam_t scanning_params[] = {
/*                      interval                  window                   duration  active */
/*                      0.625ms                  0.625ms                       10ms         */
    {   ble::scan_interval_t(4),   ble::scan_window_t(4),   ble::scan_duration_t(0), false },
    { ble::scan_interval_t(160), ble::scan_window_t(100), ble::scan_duration_t(300), false },
    { ble::scan_interval_t(160),  ble::scan_window_t(40),   ble::scan_duration_t(0), true  },
    { ble::scan_interval_t(500),  ble::scan_window_t(10),   ble::scan_duration_t(0), false }
};

/* helper that gets the number of items in arrays */
template<class T, size_t N>
size_t size(const T (&)[N])
{
    return N;
}

/** Demonstrate advertising, scanning and connecting
 */
class GapDemo : private mbed::NonCopyable<GapDemo>, public ble::Gap::EventHandler
{
public:
    GapDemo(BLE& ble, events::EventQueue& event_queue) :
        _ble(ble),
        _gap(ble.gap()),
        _event_queue(event_queue),
        _led1(LED1, 0),
        _set_index(0),
        _is_in_scanning_mode(true),
        _is_connecting(false),
        _on_duration_end_id(0),
        _scan_count(0),
        _blink_event(0) {
        for (uint8_t i = 0; i < size(_adv_handles); ++i) {
            _adv_handles[i] = ble::INVALID_ADVERTISING_HANDLE;
        }
    }

    ~GapDemo()
    {
        if (_ble.hasInitialized()) {
            _ble.shutdown();
        }
    }

    /** Start BLE interface initialisation */
    void run()
    {
        if (_ble.hasInitialized()) {
            printf("Ble instance already initialised.\r\n");
            return;
        }

        /* handle gap events */
        _gap.setEventHandler(this);

        ble_error_t error = _ble.init(this, &GapDemo::on_init_complete);
        if (error) {
            print_error(error, "Error returned by BLE::init");
            return;
        }

        /* to show we're running we'll blink every 500ms */
        _blink_event = _event_queue.call_every(500, this, &GapDemo::blink);

        /* this will not return until shutdown */
        _event_queue.dispatch_forever();
    }

private:
    /** This is called when BLE interface is initialised and starts the first mode */
    void on_init_complete(BLE::InitializationCompleteCallbackContext *event)
    {
        if (event->error) {
            print_error(event->error, "Error during the initialisation");
            return;
        }

        print_mac_address();

        /* setup the default phy used in connection to 2M to reduce power consumption */
        if (is_2m_phy_supported()) {
            ble::phy_set_t phys(/* 1M */ false, /* 2M */ true, /* coded */ false);

            ble_error_t error = _gap.setPreferredPhys(/* tx */&phys, /* rx */&phys);
            if (error) {
                print_error(error, "GAP::setPreferedPhys failed");
            }
        }

        /* all calls are serialised on the user thread through the event queue */
        _event_queue.call(this, &GapDemo::demo_mode_start);
    }

    /** queue up start of the current demo mode */
    void demo_mode_start()
    {
        if (_is_in_scanning_mode) {
            _event_queue.call(this, &GapDemo::scan);
        } else {
            _event_queue.call(this, &GapDemo::advertise);
        }

        /* for performance measurement keep track of duration of the demo mode */
        _demo_duration.start();
        /* keep track of our state */
        _is_connecting = false;

        /* queue up next demo mode */
        _on_duration_end_id = _event_queue.call_in(
            MODE_DURATION_MS,
            this,
            &GapDemo::end_demo_mode
        );

        printf("\r\n");
    }

    /** Set up and start advertising */
    void advertise()
    {
        const DemoAdvParams_t &adv_params = advertising_params[_set_index];

        /*
         * Advertising parameters are mainly defined by an advertising type and
         * and an interval between advertisements. lower interval increases the
         * chances of being seen at the cost of more power.
         * The Bluetooth controller may run concurrent operations with the radio;
         * to help it, a minimum and maximum advertising interval should be
         * provided.
         *
         * With Bluetooth 5; it is possible to advertise concurrently multiple
         * payloads at different rate. The combination of payload and its associated
         * parameters is named an advertising set. To refer to these advertising
         * sets the Bluetooth system use an advertising set handle that needs to
         * be created first.
         * The only exception is the legacy advertising handle which is usable
         * on Bluetooth 4 and Bluetooth 5 system. It is created at startup and
         * its lifecycle is managed by the system.
         */
        ble_error_t error = _gap.setAdvertisingParameters(
            ble::LEGACY_ADVERTISING_HANDLE,
            ble::AdvertisingParameters(
                adv_params.type,
                adv_params.min_interval,
                adv_params.max_interval
            )
        );
        if (error) {
            print_error(error, "Gap::setAdvertisingParameters() failed");
            return;
        }

        /* Set payload for the set */
        /* Use the simple builder to construct the payload; it fails at runtime
         * if there is not enough space left in the buffer */
        error = _gap.setAdvertisingPayload(
            ble::LEGACY_ADVERTISING_HANDLE,
            ble::AdvertisingDataSimpleBuilder<ble::LEGACY_ADVERTISING_MAX_SIZE>()
                .setFlags()
                .setName("Legacy advertiser")
                .getAdvertisingData()
        );
        if (error) {
            print_error(error, "Gap::setAdvertisingPayload() failed");
            return;
        }

        /* Start advertising the set */
        error = _gap.startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
        if (error) {
            print_error(error, "Gap::startAdvertising() failed");
            return;
        }

        printf("Advertising started (type: 0x%x, interval: [%d : %d]ms)\r\n",
            adv_params.type.value(),
            adv_params.min_interval.valueInMs(), adv_params.max_interval.valueInMs() );

        if (is_extended_advertising_supported()) {
            advertise_extended();
        }
    }

    void advertise_extended()
    {
        const DemoAdvParams_t &adv_params = advertising_params[_set_index];

        /* this is the memory backing for the payload */
        uint8_t adv_buffer[MAX_ADVERTISING_PAYLOAD_SIZE];

        /* how many sets */
        uint8_t max_adv_set = std::min(
            _gap.getMaxAdvertisingSetNumber(),
            (uint8_t) size(_adv_handles)
        );

        /* one advertising set is reserved for legacy advertising */
        if (max_adv_set < 2) {
            return;
        }

        /* how much payload in a set */
        uint16_t max_adv_size = std::min(
            (uint16_t) _gap.getMaxAdvertisingDataLength(),
            MAX_ADVERTISING_PAYLOAD_SIZE
        );

        /* create and start all requested (and possible) advertising sets */
        for (uint8_t i = 0; i < (max_adv_set - 1); ++i) {
            /* create the advertising set with its parameter */
            /* this time we do not use legacy PDUs */
            ble_error_t error = _gap.createAdvertisingSet(
                &_adv_handles[i],
                ble::AdvertisingParameters(
                    adv_params.type,
                    adv_params.min_interval,
                    adv_params.max_interval
                ).setUseLegacyPDU(false)
            );
            if (error) {
                print_error(error, "Gap::createAdvertisingSet() failed");
                return;
            }

            /* use the helper to build the payload */
            ble::AdvertisingDataBuilder adv_data_builder(
                adv_buffer,
                max_adv_size
            );

            /* set the flags */
            error = adv_data_builder.setFlags();
            if (error) {
                print_error(error, "AdvertisingDataBuilder::setFlags() failed");
                return;
            }

            /* set different name for each set */
            MBED_ASSERT(i < 9);
            char device_name[] = "Advertiser x";
            snprintf(device_name, size(device_name), "Advertiser %d", i%10);
            error = adv_data_builder.setName(device_name);
            if (error) {
                print_error(error, "AdvertisingDataBuilder::setName() failed");
                return;
            }

            /* Set payload for the set */
            error = _gap.setAdvertisingPayload(
                _adv_handles[i],
                adv_data_builder.getAdvertisingData()
            );
            if (error) {
                print_error(error, "Gap::setAdvertisingPayload() failed");
                return;
            }

            /* Start advertising the set */
            error = _gap.startAdvertising(_adv_handles[i]);
            if (error) {
                print_error(error, "Gap::startAdvertising() failed");
                return;
            }

            printf("Advertising started (type: 0x%x, interval: [%d : %d]ms)\r\n",
                adv_params.type.value(),
                adv_params.min_interval.valueInMs(), adv_params.max_interval.valueInMs() );
        }
    }

    /** Set up and start scanning */
    void scan()
    {
        const DemoScanParam_t &scan_params = scanning_params[_set_index];

        /*
         * Scanning happens repeatedly and is defined by:
         *  - The scan interval which is the time (in 0.625us) between each scan cycle.
         *  - The scan window which is the scanning time (in 0.625us) during a cycle.
         * If the scanning process is active, the local device sends scan requests
         * to discovered peer to get additional data.
         */
        ble_error_t error = _gap.setScanParameters(
            ble::ScanParameters(
                ble::phy_t::LE_1M,   // scan on the 1M PHY
                scan_params.interval,
                scan_params.window,
                scan_params.active
            )
        );
        if (error) {
            print_error(error, "Error caused by Gap::setScanParameters");
            return;
        }

        /* start scanning and attach a callback that will handle advertisements
         * and scan requests responses */
        error = _gap.startScan(scan_params.duration);
        if (error) {
            print_error(error, "Error caused by Gap::startScan");
            return;
        }

        printf("Scanning started (interval: %dms, window: %dms, timeout: %dms).\r\n",
               scan_params.interval.valueInMs(), scan_params.window.valueInMs(), scan_params.duration.valueInMs());
    }

    /** Finish the mode by shutting down advertising or scanning and move to the next mode. */
    void end_demo_mode()
    {
        if (_is_in_scanning_mode) {
            end_scanning_mode();
        } else {
            end_advertising_mode();
        }

        /* alloted time has elapsed or be connected, move to next demo mode */
        _event_queue.call(this, &GapDemo::next_demo_mode);
    }

    /** Execute the disconnection */
    void do_disconnect(ble::connection_handle_t handle)
    {
        printf("Disconnecting\r\n");
        _gap.disconnect(handle, ble::local_disconnection_reason_t::USER_TERMINATION);
    }

    bool is_2m_phy_supported()
    {
        return _gap.isFeatureSupported(ble::controller_supported_features_t::LE_2M_PHY);
    }

    bool is_extended_advertising_supported()
    {
        return _gap.isFeatureSupported(ble::controller_supported_features_t::LE_EXTENDED_ADVERTISING);
    }


private:
    /* Gap::EventHandler */

    /** Look at scan payload to find a peer device and connect to it */
    virtual void onAdvertisingReport(const ble::AdvertisingReportEvent &event)
    {
        /* keep track of scan events for performance reporting */
        _scan_count++;

        /* don't bother with analysing scan result if we're already connecting */
        if (_is_connecting) {
            return;
        }

        /* only look at events from devices at a close range */
        if (event.getRssi() < -65) {
            return;
        }

        ble::AdvertisingDataParser adv_parser(event.getPayload());

        /* parse the advertising payload, looking for a discoverable device */
        while (adv_parser.hasNext()) {
            ble::AdvertisingDataParser::element_t field = adv_parser.next();

            /* skip non discoverable device */
            if (field.type != ble::adv_data_type_t::FLAGS ||
                field.value.size() != 1 ||
                !(field.value[0] & GapAdvertisingData::LE_GENERAL_DISCOVERABLE)) {
                continue;
            }

            /* connect to a discoverable device */

            /* abort timeout as the mode will end on disconnection */
            _event_queue.cancel(_on_duration_end_id);

            printf("We found a connectable device\r\n");
            ble_error_t error = _gap.connect(
                event.getPeerAddressType(),
                event.getPeerAddress(),
                ble::ConnectionParameters() // use the default connection parameters
            );
            if (error) {
                print_error(error, "Error caused by Gap::connect");
                /* since no connection will be attempted end the mode */
                _event_queue.call(this, &GapDemo::end_demo_mode);
                return;
            }

            /* we may have already scan events waiting
             * to be processed so we need to remember
             * that we are already connecting and ignore them */
            _is_connecting = true;
            return;
        }
    }

    virtual void onAdvertisingEnd(const ble::AdvertisingEndEvent &event)
    {
        if (event.isConnected()) {
            printf("Stopped advertising early due to connection\r\n");
        }
    }

    virtual void onScanTimeout(const ble::ScanTimeoutEvent&)
    {
        printf("Stopped scanning early due to timeout parameter\r\n");
        _demo_duration.stop();
    }

    /** This is called by Gap to notify the application we connected,
     *  in our case it immediately disconnects */
    virtual void onConnectionComplete(const ble::ConnectionCompleteEvent &event)
    {
        _demo_duration.stop();

        if (event.getStatus() == BLE_ERROR_NONE) {
            printf("Connected in %dms\r\n", _demo_duration.read_ms());

            /* cancel the connect timeout since we connected */
            _event_queue.cancel(_on_duration_end_id);

            _event_queue.call_in(
                CONNECTION_DURATION,
                this,
                &GapDemo::do_disconnect,
                event.getConnectionHandle()
            );
        } else {
            printf("Failed to connect after scanning %d advertisements\r\n", _scan_count);
            _event_queue.call(this, &GapDemo::end_demo_mode);
        }
    }

    /** This is called by Gap to notify the application we disconnected,
     *  in our case it calls next_demo_mode() to progress the demo */
    virtual void onDisconnectionComplete(const ble::DisconnectionCompleteEvent &event)
    {
        printf("Disconnected\r\n");

        /* we have successfully disconnected ending the demo, move to next mode */
        _event_queue.call(this, &GapDemo::end_demo_mode);
    }

    /**
     * Implementation of Gap::EventHandler::onReadPhy
     */
    virtual void onReadPhy(
        ble_error_t error,
        ble::connection_handle_t connectionHandle,
        ble::phy_t txPhy,
        ble::phy_t rxPhy
    ) {
        if (error) {
            printf(
                "Phy read on connection %d failed with error code %s\r\n",
                connectionHandle,
                BLE::errorToString(error)
            );
        } else {
            printf(
                "Phy read on connection %d - Tx Phy: %s, Rx Phy: %s\r\n",
                connectionHandle,
                phy_to_string(txPhy),
                phy_to_string(rxPhy)
            );
        }
    }

    /**
     * Implementation of Gap::EventHandler::onPhyUpdateComplete
     */
    virtual void onPhyUpdateComplete(
        ble_error_t error,
        ble::connection_handle_t connectionHandle,
        ble::phy_t txPhy,
        ble::phy_t rxPhy
    ) {
        if (error) {
            printf(
                "Phy update on connection: %d failed with error code %s\r\n",
                connectionHandle,
                BLE::errorToString(error)
            );
        } else {
            printf(
                "Phy update on connection %d - Tx Phy: %s, Rx Phy: %s\r\n",
                connectionHandle,
                phy_to_string(txPhy),
                phy_to_string(rxPhy)
            );
        }
    }

private:

    /** Clean up internal state after last run, cycle to the next mode and launch it */
    void next_demo_mode()
    {
        /* reset the demo ready for the next mode */
        _scan_count = 0;
        _demo_duration.stop();
        _demo_duration.reset();

        /* cycle through all demo modes */
        _set_index++;

        /* switch between advertising and scanning when we go
         * through all the params in the array */
        if (_set_index >= (_is_in_scanning_mode ? size(scanning_params) : size(advertising_params))) {
            _set_index = 0;
            _is_in_scanning_mode = !_is_in_scanning_mode;
        }

        _ble.shutdown();
        _event_queue.cancel(_blink_event);
        _event_queue.break_dispatch();
    }

    /** Finish the mode by shutting down advertising or scanning and move to the next mode. */
    void end_scanning_mode()
    {
        print_scanning_performance();
        ble_error_t error = _gap.stopScan();

        if (error) {
            print_error(error, "Error caused by Gap::stopScan");
        }
    }

    void end_advertising_mode()
    {
        print_advertising_performance();

        _gap.stopAdvertising(ble::LEGACY_ADVERTISING_HANDLE);

        if (is_extended_advertising_supported()) {
            end_extended_advertising();
        }
    }

    void end_extended_advertising()
    {
        /* iterate over the advertising handles */
        for (uint8_t i = 0; i < size(_adv_handles); ++i) {
            /* check if the set has been sucesfully created */
            if (_adv_handles[i] == ble::INVALID_ADVERTISING_HANDLE) {
                continue;
            }

            /* if it's still active, stop it */
            if (_gap.isAdvertisingActive(_adv_handles[i])) {
                ble_error_t error = _gap.stopAdvertising(_adv_handles[i]);
                if (error) {
                    print_error(error, "Error caused by Gap::stopAdvertising");
                    continue;
                }
            }

            ble_error_t error = _gap.destroyAdvertisingSet(_adv_handles[i]);
            if (error) {
                print_error(error, "Error caused by Gap::destroyAdvertisingSet");
                continue;
            }

            _adv_handles[i] = ble::INVALID_ADVERTISING_HANDLE;
        }
    }

    /** print some information about our radio activity */
    void print_scanning_performance()
    {
        /* measure time from mode start, may have been stopped by timeout */
        uint16_t duration_ms = _demo_duration.read_ms();

        /* convert ms into timeslots for accurate calculation as internally
         * all durations are in timeslots (0.625ms) */
        uint16_t duration_ts = ble::scan_interval_t(ble::millisecond_t(duration_ms)).value();
        uint16_t interval_ts = scanning_params[_set_index].interval.value();
        uint16_t window_ts = scanning_params[_set_index].window.value();
        /* this is how long we scanned for in timeslots */
        uint16_t rx_ts = (duration_ts / interval_ts) * window_ts;
        /* convert to milliseconds */
        uint16_t rx_ms = ble::scan_interval_t(rx_ts).valueInMs();

        printf("We have scanned for %dms with an interval of %d"
               " timeslots and a window of %d timeslots\r\n",
            duration_ms, interval_ts, window_ts);

        printf("We have been listening on the radio for at least %dms\r\n", rx_ms);
    }

    /** print some information about our radio activity */
    void print_advertising_performance()
    {
        /* measure time from mode start, may have been stopped by timeout */
        uint16_t duration_ms = _demo_duration.read_ms();
        uint8_t number_of_active_sets = 0;

        for (uint8_t i = 0; i < size(_adv_handles); ++i) {
            if (_adv_handles[i] != ble::INVALID_ADVERTISING_HANDLE) {
                if (_gap.isAdvertisingActive(_adv_handles[i])) {
                    number_of_active_sets++;
                }
            }
        }

        /* convert ms into timeslots for accurate calculation as internally
         * all durations are in timeslots (0.625ms) */
        uint16_t duration_ts = ble::adv_interval_t(ble::millisecond_t(duration_ms)).value();
        uint16_t interval_ts = advertising_params[_set_index].max_interval.value();
        /* this is how many times we advertised */
        uint16_t events = (duration_ts / interval_ts) * number_of_active_sets;

        printf("We have advertised for %dms with an interval of at least %d timeslots\r\n",
            duration_ms, interval_ts);

        if (number_of_active_sets > 1) {
            printf("We had %d active advertising sets\r\n", number_of_active_sets);
        }

        /* non-scannable and non-connectable advertising
         * skips rx events saving on power consumption */
        if (advertising_params[_set_index].type == ble::advertising_type_t::NON_CONNECTABLE_UNDIRECTED) {
            printf("We created at least %d tx events\r\n", events);
        } else {
            printf("We created at least %d tx and rx events\r\n", events);
        }
    }

    /** Blink LED to show we're running */
    void blink(void)
    {
        _led1 = !_led1;
    }

private:
    BLE                &_ble;
    ble::Gap           &_gap;
    events::EventQueue &_event_queue;
    DigitalOut          _led1;

    /* Keep track of our progress through demo modes */
    size_t              _set_index;
    bool                _is_in_scanning_mode;
    bool                _is_connecting;

    /* Remember the call id of the function on _event_queue
     * so we can cancel it if we need to end the mode early */
    int                 _on_duration_end_id;

    /* Measure performance of our advertising/scanning */
    Timer               _demo_duration;
    size_t              _scan_count;

    int                 _blink_event;

    ble::advertising_handle_t _adv_handles[ADV_SET_NUMBER];
};

/** Schedule processing of events from the BLE middleware in the event queue. */
void schedule_ble_events(BLE::OnEventsToProcessCallbackContext *context) {
    event_queue.call(Callback<void()>(&context->ble, &BLE::processEvents));
}

int main()
{
    BLE &ble = BLE::Instance();

    /* this will inform us off all events so we can schedule their handling
     * using our event queue */
    ble.onEventsToProcess(schedule_ble_events);

    GapDemo demo(ble, event_queue);

    while (1) {
        demo.run();
        wait_ms(TIME_BETWEEN_MODES_MS);
        printf("\r\nStarting next GAP demo mode\r\n");
    };

    return 0;
}