Google Schedular

Use your Google Calendar as a Scheduler for your Arduino projects. Get summary(*) of current events from the target calendar.

(*) a summary is like an event name/title/label. This is what you see as event name in your calendar.

Setup

It requires an Google OAuth2 credentials. https://developers.google.com/identity/protocols/oauth2/limited-input-device#prerequisites

• Get your Google Account
• Got to https://console.cloud.google.com/
• Create a Google Dev Project (ie "MyGoogleSchedular")
• Go to Consent tab: he (infinite?) time it will take to develop your Google project, as you will have to manually add the Internet addresses of your users (including yourself)
• Go to Credentials tab: create a OAuth2.0 Credentials for your device, you will get the CLIENT_ID and the CLIENT_SECRET

Official explanations:

• Device OAuth https://developers.google.com/identity/protocols/oauth2/limited-input-device => GOOGLE_API_CLIENT_ID => GOOGLE_API_CLIENT_SECRET

Run

As soon as you get the verification_url and user_code, go to this URL (most probably https://www.google.com/device) then authenticate with the given code and your Google Account.

Code

Create the Schedular with a NTP client for knowing the expiration times, and the current datetime when requesting the Google Calendar.

WiFiUDP udp;
TimestampRFC3339Ntp ntp(udp);
GoogleSchedular gs(GOOGLE_API_CLIENT_ID, GOOGLE_API_CLIENT_SECRET, ntp);

Get user temporary code for merging the user account to this session.

String url;
String code; 
gs.startRegistration(url, code);

Serial.print("URL : "); Serial.println(url);
Serial.print("CODE: "); Serial.println(code);

Waiting the refresh_access / access_token from Google when the user is authenticated on Google.

FastTimer<FastTimer_precision_t::P_1s_4m> timer1s;
do {
    timer1s.update();
    if (timer1s.isTickBy64()) {
        ntp.request(NTP_HOST);
    } else {
        delay(100);
    }

    ntp.listen();
    gs.maintain();
} while(gs.isInitialized());

Getting the targeted calendar identifier from its name.

gs.setCalendar(CALENDAR_NAME);

Generating the timestamp string, then request the current event titles/summaries/labels.

ntp.syncRFC3339();
String ts = ntp.getTimestampRFC3339();
gs.syncAt(ts);

for(String e : gs.getEventList()) {
    Serial.println(e);
}

Don't forget to maintain the user session with gs.maintaint() Example:

void loop()
{
    if (timer1mn.hasChanged()) {
        ntp.request(NTP_HOST);

        ntp.syncRFC3339(timer1mn.getElapsedTime());
        String ts = ntp.getTimestampRFC3339();
        gs.syncAt(ts);

        Serial.print("-- ");
        Serial.println(ts);
        for(String e : gs.getEventList()) {
            Serial.println("- " + e);
        }
    } else {
        delay(100);
    }

    if (ntp.listen()) {
        gs.maintain();
    }
}

Limitations

Visit:

• https://developers.google.com/calendar/api/guides/quota
• https://cloud.google.com/api-keys/docs/quotas