Restores the modem state after device is woken up.

[XuGuohui]

Problem

For sleep 2.0 API, if the modem is powered on, but not establishing connection, it won't restore the modem power state after device is woken up.

Solution

Tracks the modem power state and connection state respectively in system sleep.

Steps to Test

Running the example below building against develop branch you won't see the modem is on after device is woken up, but you will if you build it against the current branch.

Example App

#include "Particle.h"

SYSTEM_MODE(SEMI_AUTOMATIC);
SYSTEM_THREAD(ENABLED);

Serial1LogHandler l(115200, LOG_LEVEL_INFO);

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

    waitUntil(Cellular.isOn);
    Log.info("Done");
    delay(2s);

    Log.info("Entering sleep...");
    SystemSleepResult r = System.sleep(SystemSleepConfiguration().mode(SystemSleepMode::STOP).duration(5s));

    if (r.error() == SYSTEM_ERROR_NONE) {
        Log.info("Exited sleep.");
    } else {
        Log.error("Failed to enter sleep.");
    }

    Log.info("Waiting for the modem to be turned on...");
    waitFor(Cellular.isOn, 60000);
    Log.info("Modem is %s", Cellular.isOn() ? "on" : "off");
}

void loop() {
}

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)

[avtolstoy]

Rejecting because of status.on logic.

wiring/sleep20 also needs to be updated to have a set of tests to validate this behavior.

[avtolstoy]

What if it's being powered off right now (IF_POWER_STATE_POWERING_DOWN on Gen 3)? This might need to have separate implementation for Gen 2 and Gen 3: SPARK_WLAN_XXX for Gen 2 and going into network manager on Gen 3 for pwrState value.

[XuGuohui]

Good catch! Will work around it.

[avtolstoy]

There is no need to pass network_status_t by reference here, which semantically means that it may be modified. Either by value (preferred) or at least const reference.