Fix BLE/Wi-Fi concurrency issues

[XuGuohui]

Problem

When both BLE and Wi-Fi are working, BLE scanning may has no result returned.

Solution

Dynamically set the PTA (Packets Traffic Arbitration) mode according to the Wi-Fi state.

Example App

#include "Particle.h"

SYSTEM_MODE(SEMI_AUTOMATIC);
SYSTEM_THREAD(ENABLED);

Serial1LogHandler logHandler(115200, LOG_LEVEL_ALL);

constexpr system_tick_t SCAN_DURATION_MS = 30000;
system_tick_t scan_start_ms = 0;

volatile size_t ble_advert_found = 0;
size_t ble_scans_started = 0;
void scan_result_cb(const BleScanResult *result, void *context) {
    ble_advert_found++;
}

void scan_thread_f() {
    while (true) {
        unsigned int t0, t1;
        if (scan_start_ms && ((millis() - scan_start_ms) <= SCAN_DURATION_MS)) {
            ble_scans_started++;
            t0 = millis();
            BLE.scan(scan_result_cb, nullptr);
            t1 = millis();
            if (t1 - t0 > 500) {
                // Log.info("    scan took too long: %dms", t1 - t0);
            }
        }
        delay(1);
    }
}

size_t wifi_ap_found = 0;
void wifi_scan_callback(WiFiAccessPoint* wap, void* data) {
    // Log.info("ssid=%s security=%d channel=%d rssi=%d", wap->ssid, (int)wap->security, (int)wap->channel, wap->rssi);
    wifi_ap_found++;
}

void setup() {
    BLE.on();

    BleScanParams params = {};
    params.version = BLE_API_VERSION;
    params.size = sizeof(BleScanParams);
    BLE.getScanParameters(params);
    params.active = false;
    params.interval = 1600; // 1600 * 0.625ms = 1s
    params.window = 1600; // 1600 * 0.625ms = 1s
    params.timeout = 100; // 100 * 10ms = 1s
    BLE.setScanParameters(params);

    static Thread *thread = new Thread("sensor_ble_scan", scan_thread_f, OS_THREAD_PRIORITY_NETWORK);

    WiFi.on();
}

void loop() {
    static uint8_t wifi_scan = 2;

    if (!scan_start_ms || ((millis() - scan_start_ms) > (SCAN_DURATION_MS + 300))) {
        if (scan_start_ms) {
            Log.info("    ble adverts found total: %u (scans %d) (WiFi: %d)",
                ble_advert_found,
                ble_scans_started,
                wifi_scan);
            
            if (ble_advert_found == 0  && !wifi_scan) {
                while (1); // We have encountered problem
            }
        }
        wifi_scan++;
        wifi_scan %= 3;
        ble_advert_found = 0;
        ble_scans_started = 0;
        scan_start_ms = millis();
    }

    if (wifi_scan == 1) {  //  Wi-Fi scanning
        wifi_ap_found = 0;
        WiFi.scan(wifi_scan_callback);
        Log.info("wifi ap found: %u", wifi_ap_found);
    } else if (wifi_scan == 2) {  // Wi-Fi connected
        if (!WiFi.ready()) {
            WiFi.connect();
            waitUntil(WiFi.ready);
            Log.info("wifi connected");
        }
    } else { // No Wi-Fi
        if (WiFi.ready()) {
            WiFi.disconnect();
            while (WiFi.ready());
            Log.info("wifi disconnected");
        }
    }
}

References

N/A

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)