The Bluetooth module wants 3.3v logic levels so that is taken into account. The image above shows a buffer chip doing the conversion, but the Fritzing schematic on the post uses a voltage divider.

The watch is built around an Arduino Pro Mini, a scavenged Nokia LCD, and a BlueSMiRF Gold. The Bluetooth connects to a Nokia N900 with a little Bluetooth client app [Ahmet] wrote.

The $22 kit includes an Arduino-BLE board and 6-pin header that should be fairly broadly applicable for building Arduino-based hardware that can communicate with iOS devices.

Arduino has introduced a Nano shaped board with a Wi-Fi and Bluetooth LE capable Espressif’s ESP32-S3 microcontroller, supporting it with the Arduino IDE and MicroPython. “Beginners can explore in an ...

Primo will include Bluetooth LE (low energy), NFC, Wi-Fi, and infrared built-in — you typically need a “shield” add-on to get these features.