DeviceScript and LCD screens

#typescript #esp32 #beginners #iot

This article shows how to use DeviceScript to program a microcontroller (ESP32-C3), a temperature/humidity sensor (BME680) and a LCD character screen to build a tiny weather dashboard. This project does not require soldering or embedded skills.

In a previous article, we looked at using an OLED screen to display temperature readings 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.

You can follow along this tutorial without any hardware and use the simulators provided by DeviceScript. Otherwise, the parts needed are

Seeed Studio Xiao + Grove shield

The Xiao ESP32-C3 is a low-cost compact microcontroller board running the Espressif ESP32-C3.

The Grove shield for Xiao is a convenient base for the Xiao that provides an easy access to OLED screens, Grove connectors and battery charging.

DeviceScript provides a shield drivers that configures the pins and the OLED display for this hardware combo.



import { XiaoGroveShield} from "@devicescript/drivers"

const shield = new XiaoGroveShield()

LCD screen as character screen

The Grove LCD screen supports 16 columns and rows of characters; it provides an I2C interface that dramatically reduces the complexity of connecting this kind of devices (just plug the grove connector and go). The driver is written in TypeScript/DeviceScript.

The sceen is modelled as a character screen. Using services allows DeviceScript to provide simulation and device twin capabilities to your coding experience.



import {
    XiaoGroveShield,
    startGroveRGBLCD16x2,
} from "@devicescript/drivers"

const shield = new XiaoGroveShield()
const screen = await startGroveRGBLCD16x2()
await screen.message.write('starting...')

BME680

The BME680 is a high-precision temperature/humidity/gas sensor that can be conveniently connected through one of the grove connector.

The sensor is exposed as 3 services, temperature, humidity, air quality, that can be used to poll the sensor data and display it on the screen.



import {
    startBME680,
} from "@devicescript/drivers"

...
const { temperature, humidity } = await startBME680({
    address: 0x76
})
const temp = await temperature.reading.read()
const humi = await humidity.reading.read()
await screen.message.write(`t ${temp}\nh ${humi}`)

Simulation

You try this code without hardware. DeviceScript will spin up simulators for the Xiao, the sensors and screens.

Value dashboard

Since display sensor values is a common task, DeviceScript provides a helper ValueDashboard to render a list of sensor data.

The value dashboard



import { ValueDashboard } from "@devicescript/runtime"

...
const dashboard = new ValueDashboard(screen, {
    temperature: { digits: 1, unit: "C" },
    humi: { digits: 0, unit: "%" },
})

setInterval(async () => {
    dashboard.values.temperature = temperature.reading.read()
    dashboard.values.humi = humidity.reading.read()
    await dashboard.show()
}, 1000)

All together

The final sample is a tiny weather display that shows the temperature/humidity reported by the BME680 sensor.



import {
    startGroveRGBLCD16x2,
    startBME680,
    XiaoGroveShield,
} from "@devicescript/drivers"
import { ValueDashboard } from "@devicescript/runtime"

const shield = new XiaoGroveShield()
const { temperature, humidity } = await startBME680({
    address: 0x76,
})
const screen = await startGroveRGBLCD16x2()

const dashboard = new ValueDashboard(screen, {
    temp: { digits: 1, unit: "C" },
    humi: { digits: 0, unit: "%" },
})

setInterval(async () => {
    dashboard.values.temp = await temperature.reading.read()
    dashboard.values.humi = await humidity.reading.read()
    await dashboard.show()
}, 1000)