This article uses an ESP32-C3 board Adafruit QT Py C3
and a SHTC3 sensor to publish a temperature reading to
the Adafruit.io MQTT APIs every minute using DeviceScript.
DeviceScript
DeviceScript brings JavaScript/TypeScript to tiny IoT devices such as the ESP32. DeviceScript provides a user friendly editing/debugging experience in Visual Studio Code.
Reading temperature
We start by configuring the script for the QT Py and adding a scheduled interval to read the temperature
from the SHTC3 sensor every 60 seconds.
// hardware configuration and drivers import "@dsboard/adafruit_qt_py_c3" import { startSHTC3 } from "@devicescript/drivers" import { schedule } from "@devicescript/runtime" // mounting a temperature server for the SHTC3 sensor const { temperature } = await startSHTC3() schedule( async () => { // read data from temperature sensor const value = await temperature.reading.read() }, { timeout: 1000, interval: 60000 } ) Configuration and Secrets
To connect to Adafruit.io, you will to get an account with https://io.adafruit.com
and store your username and password in the settings
as the IO_USERNAME and IO_KEY keys (make sure your key is in env.local).
Also create a feed and update the feed key in the example below.
import { readSetting } from "@devicescript/settings" // TODO: update feed key const feed = "temperature" const username = await readSetting("IO_USERNAME") // this secret is stored in the .env.local // and uploaded to the device settings const password = await readSetting("IO_KEY") Starting the MQTT client
Following the Adafruit documentation,
we start a MQTT connection and craft a topic that will route the data to our account.
import { startMQTTClient } from "@devicescript/net" ... const mqtt = await startMQTTClient({ host: `io.adafruit.com`, proto: "tls", port: 8883, username, password, }) const topic = `${username}/feeds/${feed}/json` Publish data
With the MQTT client and the topic, we can add a call to mqtt.publish in the scheduled worker
to upload the data to Adafruit (note that { value } expands to JSON { "value": value } automatically)
schedule( async () => { ... // publish data to Adafruit await mqtt.publish(topic, { value }) }, { timeout: 1000, interval: 60000 } ) All together
Putting all the pieces together we get the following program.
import "@dsboard/adafruit_qt_py_c3" import { startSHTC3 } from "@devicescript/drivers" import { startMQTTClient } from "@devicescript/net" import { readSetting } from "@devicescript/settings" import { schedule } from "@devicescript/runtime" const { temperature } = await startSHTC3() const feed = "temperature" const username = await readSetting("IO_USERNAME") device settings const password = await readSetting("IO_KEY") const mqtt = await startMQTTClient({ host: `io.adafruit.com`, proto: "tls", port: 8883, username, password, }) const topic = `${username}/feeds/${feed}/json` schedule( async () => { const value = await temperature.reading.read() await mqtt.publish(topic, { value }) }, { timeout: 1000, interval: 60000 } ) Extra points: Filtering data
You could use observables to smooth the sensor
data. For example, apply an exponentially moving average
on the feed of temperature readings.
import { ewma, auditTime } from "@devicescript/observables" ... temperature.reading .pipe(ewma(0.5), auditTime(60000)) .subscribe(async value => await mqtt.publish(topic, { value })) 
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