# Circuit Playground Bluefruit > Round educational microcontroller with Nordic nRF52840 (64MHz Cortex-M4F + BLE), 10 NeoPixels, accelerometer, microphone, light sensor, speaker, 8 alligator-clip I/O pads, and USB. Runs CircuitPython, MakeCode, and Arduino. ## Quick Facts - **Brand:** Adafruit - **Board Type:** educational-board - **Price:** ~$24.95 - **Product Readiness:** consumer - **CPU:** ARM Cortex-M4F @ 64MHz (Nordic nRF52840) - **CPU Architecture:** ARM Cortex-M4F - **CPU Cores:** 1 - **RAM:** 256KB SRAM - **Flash:** 1MB + 2MB SPI Flash - **Power:** 5V via Micro-USB, 3xAAA battery, or LiPo - **Operating Voltage:** 3.3V - **Dimensions:** 50.6mm diameter - **Weight:** 8.9g - **Antenna:** Built-in PCB antenna ## Connectivity - **Wifi:** false - **Bluetooth:** Bluetooth 5.0 BLE (nRF52840) - **Zigbee:** false - **Ethernet:** false ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Certifications RoHS, FCC, CE ## Compatible Firmware circuitpython, makecode, arduino ## Use Cases - iot - wearable - smart-home ## Components - **nRF52840** (mcu): Nordic Semiconductor nRF52840 ARM Cortex-M4F @ 64MHz, 1MB Flash, 256KB RAM, Bluetooth 5.0 BLE. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Finfocenter.nordicsemi.com%2Fpdf%2FnRF52840_PS_v1.7.pdf&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) - **LIS3DH** (mcu): Triple-axis MEMS accelerometer with tap and free-fall detection, I2C. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fdatasheet%2Flis3dh.pdf&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) ## Protocols - **I2C**: SDA: GPIO25, SCL: GPIO26 - **SPI**: MOSI: GPIO15, MISO: GPIO14, SCK: GPIO12 - **UART**: TX: GPIO6, RX: GPIO8 - **PWM**: - **ADC**: - **BLE**: ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | GPIO4 | A0 — DAC/ADC | ADC | analog-input, dac, digital-input, digital-output, pwm | | GPIO5 | A1 — ADC | ADC | analog-input, digital-input, digital-output, pwm | | GPIO30 | A2 — ADC | ADC | analog-input, digital-input, digital-output | | GPIO28 | A3 — ADC | ADC | analog-input, digital-input, digital-output | | GPIO2 | A4 — ADC | ADC | analog-input, digital-input, digital-output, pwm | | GPIO3 | A5 — ADC | ADC | analog-input, digital-input, digital-output, pwm | | GPIO6 | A6 — ADC/TX | UART | analog-input, digital-input, digital-output | | GPIO8 | A7 — ADC/RX | UART | analog-input, digital-input, digital-output | | GPIO25 | SDA — I2C | I2C | digital-input, digital-output | | GPIO26 | SCL — I2C | I2C | digital-input, digital-output | | GPIO15 | MOSI — SPI | SPI | digital-input, digital-output | | GPIO14 | MISO — SPI | SPI | digital-input, digital-output | | GPIO12 | SCK — SPI | SPI | digital-input, digital-output | ## Available Software - **[circuitpython]()** (open-source) - **[makecode]()** (open-source) - **[arduino]()** (open-source) ## Description ## Overview The Circuit Playground Bluefruit is Adafruit's most feature-packed entry-level learning board, combining a rich onboard sensor suite with Bluetooth Low Energy wireless connectivity in a circular form factor designed for beginners and educators. Built around the Nordic nRF52840 ARM Cortex-M4F running at 64MHz, it provides 1MB of Flash and 256KB of RAM alongside a dedicated 2MB SPI Flash chip for program and file storage. The board's circular design places all components and I/O pads around the perimeter, making it instantly recognizable and easy to use with alligator clips. Ten mini NeoPixel RGB LEDs form a ring around the edge and are individually addressable. Eight large alligator-clip pads provide GPIO, analog input, PWM, I2C, and UART access without requiring soldering. A built-in MEMS microphone, phototransistor light sensor (capable of color and pulse sensing), LIS3DH triple-axis accelerometer, and thermistor round out the sensor suite. Bluetooth Low Energy via the nRF52840's built-in radio enables wireless communication with smartphones, computers, and other BLE devices using Adafruit's Bluefruit libraries. A mini Class-D speaker amplifier drives the on-board 7.5mm speaker for tones, beeps, and simple audio. Power options include Micro-USB, a 3×AAA battery pack connector, or a LiPo battery. The board is fully supported by CircuitPython, Microsoft MakeCode for Circuit Playground, and the Arduino IDE with the nRF52 board package. It ships with the UF2 bootloader pre-loaded, enabling drag-and-drop firmware updates without any special tools. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4333&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) — 24.95 ## Resources - [product page](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4333&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4333&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) - [documentation](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-circuit-playground-bluefruit&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) - [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit_CircuitPlayground&ref=openhardware.directory&product=circuit-playground-bluefruit&source=md-export) ## Tags `circuit-playground`, `nrf52840`, `bluetooth`, `ble`, `neopixel`, `circuitpython`, `makecode`, `educational`, `adafruit` ## Images ![Circuit Playground Bluefruit](https://nbg1.your-objectstorage.com/openhardware-directory/entities/circuit-playground-bluefruit/ffa80fcbf6d3.jpg) ![Circuit Playground Bluefruit](https://nbg1.your-objectstorage.com/openhardware-directory/entities/circuit-playground-bluefruit/48820a28d8ce.jpg) ![Circuit Playground Bluefruit](https://nbg1.your-objectstorage.com/openhardware-directory/entities/circuit-playground-bluefruit/281110124762.jpg) --- [View full device page](https://openhardware.directory/devices/circuit-playground-bluefruit)