Read a sensor

SHT3X over I2C: pick a part token, attach it to the bus, fetch, and read typed channels — plus a hardware test that checks the readings are sane.

Click through the files — it's the whole project

What's going on

• There's no per-sensor library to install. SENSOR.sensirion_sht3xd names the part, I2C0.device(0x44) names the bus and address, and the build produces the driver binding.
• fetch() takes one measurement; get() reads a channel from it. Two channels, one fetch — temperature and humidity come from the same reading.
• The channels are typed to the part: sht3x.get(CHAN.PRESS) is a build error naming the channels the SHT3XD actually serves. The wrong sensor call is caught before it ships, not when it reads garbage.
• The hardware test in test/sensor.test.ts runs on the board itself — a plausibility range check (−40 to 85 °C is the SHT3X's operating range) that catches a dead sensor or a miswired bus, which a unit test never could.

Flash and read

npx @typecad/hal create my-project --target xiao_ble/nrf52840
cd my-project
npx @typecad/hal build --compile --upload --port COM4

Wire the SHT3X breakout to the board's I2C pins (SDA, SCL, 3V3, GND — the ADDR pin floating gives 0x44). Open a serial monitor at 115200 and the readings roll every two seconds:

21.64 C, 44.2 %RH
21.65 C, 44.3 %RH

Then run the test — same board, same sensor, assertions on real hardware:

npx @typecad/hal test

  Sensor
    ✓ reads a plausible temperature
    ✓ reads a plausible humidity

  2 passing

Where to go next

• Sensors — the 200-part list, SPI attachments, and typed channels
• Communication buses — I2C and SPI device handles
• BLE temperature sensor — this sensor, advertised over BLE