BLE temperature sensor

Advertise a GATT temperature characteristic fed by an SHT3X — read it from your phone, and get notified every two seconds.

Click through the files — it's the whole project

BLE temperature sensor — Visual Studio Code

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xiao_ble · GATT 2A6E BLE · Sensor · notify

What's going on

One sensor, one characteristic. The SHT3X sits on I2C at 0x44, and the GATT Temperature characteristic (2A6E) is an Int16 in hundredths of a degree — the spec's units, not a float.
onRead(centi) answers a phone's read request with the last fetched value; notify(0, centi()) pushes a fresh one to subscribers every two seconds. The 0 is declaration order — the first characteristic declared is index 0.
char() without a service() rides the default Environmental Sensing service, which is where 2A6E belongs.
Requires a board with a BLE radio — the XIAO nRF52840 target in the config file is the primary one. On a board without one, this program is a compile-time error, not a runtime surprise.

Flash and read it

terminal

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

Open a BLE scanner app (nRF Connect, LightBlue), find TempSensor, and subscribe — the temperature rolls in every two seconds. Breathe on the sensor and watch it climb.

Where to go next

Bluetooth Low Energy — services, permissions, notify, and connection events
Sensors — part tokens, channels, and the typed get()
Communication buses — I2C devices and addresses

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