[wiring] Network: introduce isOn() and isOff() APIs to enquiry the modem power state

[XuGuohui]

As the title describes.

Example App

#include "Particle.h"

SYSTEM_MODE(MANUAL);
SYSTEM_THREAD(ENABLED);

SerialLogHandler log(115200, LOG_LEVEL_ALL);

void onNetworkStatusUpdated(system_event_t event, int param) {
    if (event == network_status) {
        switch (param) {
            case network_status_on: {
                Log.info("network_status_on");
                break;
            }
            case network_status_off: {
                Log.info("network_status_off");
                break;
            }
            case network_status_connected: {
                Log.info("network_status_connected");
                break;
            }
        }
    }
}

void setup() {
    System.on(network_status, onNetworkStatusUpdated);

    while (!Serial.isConnected());
    delay(1000);

    Log.info("Application started.");

    if (Cellular.isOn()) {
        Log.info("Modem is on.");
    } else if (Cellular.isOff()) {
        Log.info("Modem is off.");
    } else {
        Log.info("Modem is in an unknown state.");
    }

    Log.info("Turning on the modem...");
    Cellular.on();

    while (Cellular.isOff()) {
        Log.info("modem is off.");
    }
    while (!Cellular.isOn()) {
        Log.info("powering on...");
        delay(500);
    }
    Log.info("Modem is turned on.");

    delay(3s);

    Log.info("Turning off the modem...");
    Cellular.off();

    while (Cellular.isOn()) {
        Log.info("modem is on.");
    }
    while (!Cellular.isOff()) {
        Log.info("powering off...");
        delay(500);
    }
    Log.info("Modem is turned off.");
}

void loop() {
}

---

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)

[technobly]

Looking forward to having these essential APIs! Would be nice to see how they can be used with the Future API and waitFor/waitUntil, perhaps in some tests? :D

[XuGuohui]

@technobly @avtolstoy I just revised the PR. Looking forward to your review and any comments.

[avtolstoy]

@XuGuohui We can do this in a separate PR, but let's also make sure that isOff() on Electron will actually report true on boot if the modem is indeed off, as we talked about it. This should be possible by calling into the modem layer, querying the RI pin state and caching the state, so that the future isOff() calls do not have to suffer a 1s delay.

[avtolstoy]

I think we previously figured out that on boot BCM43362 is powered off, so we should be able to safely set this to false by default?

[XuGuohui]

I think it's on by default: #2205 (comment)