This USB dongle/key type thing is a little unusual - it isn't a BLE adapter that you plug into a computer to add wireless capability. (If you do want something like that, our Bluetooth 4.0 USB Module will do the job nicely.) Instead, this is basically a minimal nRF52840 wireless microcontroller dev board on a stick. You can program it in Arduino or CircuitPython and it's completely standalone. This could be useful for some situations where you want to have a standalone BLE device that communicates with a USB host but without dealing with the operating system's BLE stack.Each MDBT50Q-RX dongle comes pre-programmed with the TinyUF2 bootloader, which makes loading code onto it very easy (note that only the ones from Adafruit do this, its a special-order item). To enter the bootloader, hold down the dongle's button while inserting into USB. The button can be used in Arduino/CircuitPython as an input. There's also a single blue LED indicator. It's all very simple but we could see situations where perhaps this acts as a beacon, a OS-less BLE interface or bridge, or a compact development board for experimenting with the nRF52840.The blue LED is connected to P1.13, set that pin to be an output and pull low to turn on the LEDThe button is connected to P0.15, set that pin to be an input with an internal pullup - when pressed the pin will go low.Technical Specs for nRF52840:32-bit ARM Cortex M4F CPUSupply: 1.7V – 5.5VFlexible and configurable 48 GPIOBluetooth 5, IEEE 802.15.4, 2.4 GHz transceiver -95dBm sensitivity in 1Mbps Bluetooth low energy (BLE) mode -103dBm sensitivity in 125Kbps BLE mode (long range) +8 dBm TX power (down to -20 dBm in 4 dB steps) On-air compatible with nRF52, nRF51, nRF24L and nRF24AP Series Programmable output power from +8dBm to -20dB RSSI (1dB resolution)? See more

Flexible and configurable 48 GPIO. Single blue LED indicator. Pre-programmed with the TinyUF2 bootloader - Only from Adafruit. Arduino or CircuitPython Compatible. Minimal nRF52840 wireless microcontroller dev board on a stick.