timestamp

You can retrieve the elapsed time or attach timestamp information to data sent to obniz.js.

cloud.enqueueTimestampByTick(tick)

By calling os.getTick(), you can determine how many milliseconds have elapsed since the obnizOS started.

Normally, when you send data using a method like cloud.pluginSend("data");, there is no way to know exactly when that data was generated unless you include the time within the data payload itself.

However, by using the cloud.enqueueTimestampByTick(tick) function before sending data, you can attach the specific time corresponding to the "tick" as a Unix timestamp (in milliseconds).

In the following example, two pieces of data are sent to the cloud every 3 seconds. The first piece is given a timestamp from 1 second ago, and the second piece is given a timestamp of the current time.

Example Code (Lua)

tick = 0

function on_online_loop() 
  local current = os.getTick()
  if tick == 0 then
    tick = current
  end
  if current - tick >= 3 * 1000 then
    tick = current
    os.log(" - 3 seconds passed");

    -- Add old data with a specific timestamp (1 second ago)
    cloud.enqueueTimestampByTick(current - 1000);
    cloud.pluginSend("this is 1 sec old data");

    -- Add data with the current timestamp
    cloud.enqueueTimestampByTick(current);
    cloud.pluginSend("now");
  end
end

Receiving Data on the JavaScript Side

On the JavaScript side, when data is received via onreceive, you can access the timestamp through obniz.deviceTimestamp.

This value represents the number of milliseconds elapsed since January 1, 1970 (Unix Epoch).

Note: Since the internal clock of the device may drift unless synchronized, it is necessary to call obniz.setClock() at the start and at regular intervals.

Example Code (JavaScript)

  // Synchronize the device clock
  obniz.setClock();

  obniz.plugin.onreceive = (data) => {
    // Calculate how old the data is by comparing the current time with deviceTimestamp
    const ageInSeconds = (Date.now() - obniz.deviceTimestamp) / 1000;
    console.log(`data "${Buffer.from(data).toString()}" is ${ageInSeconds} seconds old`);
  };