# Circuit Playground Express > All-in-one ATSAMD21 learning board with 10 NeoPixels, LIS3DH accelerometer, MEMS microphone, speaker with class D amp, IR transmit/receive, 7 capacitive touch pads, and 2MB SPI flash for CircuitPython code storage. ## Quick Facts - **Brand:** Adafruit - **Board Type:** dev-board - **Price:** ~$24.95 - **Product Readiness:** developer - **CPU:** ATSAMD21G18 ARM Cortex-M0+ @ 48 MHz - **CPU Architecture:** ARM Cortex-M0+ - **CPU Cores:** 1 - **RAM:** 32KB SRAM - **Flash:** 256KB + 2MB SPI Flash - **Power:** 5V via Micro-USB / AAA battery pack / 3.7V LiPo - **Operating Voltage:** 3.3V - **Dimensions:** 50.6mm diameter - **Weight:** 8.9g - **Antenna:** none ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Compatible Firmware arduino, circuitpython ## Use Cases - educational-platform - wearable - prototyping - stem-education - circuitpython-learning ## Components - **ATSAMD21G18** (mcu): ARM Cortex-M0+ at 48MHz, 256KB flash, 32KB SRAM, native USB supporting serial, HID, MIDI. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fimages%2Fproduct-files%2F2772%2Fatmel-42181-sam-d21_datasheet.pdf&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - **LIS3DH** (accelerometer): ST triple-axis MEMS accelerometer with tap detection and free-fall detection. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fdatasheet%2Flis3dh.pdf&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - **SPW2430HR5H-B** (microphone): MEMS microphone for audio input and sound sensing. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F040%2F891%2Foriginal%2FSPW2430HR5H-B.pdf&ref=openhardware.directory&product=circuit-playground-express&source=md-export) ## Protocols - **I2C**: SDA: PA22, SCL: PA23 - **UART**: TX: PA10, RX: PA11 - **SPI**: MOSI: PA16, MISO: PA19, SCK: PA17 - **USB HID**: - **USB MIDI**: ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | PA11 | A7/RX — Analog In / UART Receive / Capacitive Touch | UART | analog-input, digital-input, digital-output | | PA10 | A6/TX — Analog In / UART Transmit / Capacitive Touch | UART | analog-input, digital-input, digital-output | | PA22 | SDA/A5 — I2C Data | I2C | digital-input, digital-output | | PA23 | SCL/A4 — I2C Clock | I2C | digital-input, digital-output | | PA16 | SPI MOSI | SPI | digital-input, digital-output | | PA19 | SPI MISO | SPI | digital-input, digital-output | | PA17 | SPI SCK | SPI | digital-input, digital-output | | PA02 | A0 — Analog In / DAC / Capacitive Touch / PWM | — | analog-input, analog-output, digital-input, digital-output, pwm | | PB08 | A1 — Analog In / Capacitive Touch / PWM | — | analog-input, digital-input, digital-output, pwm | | PB09 | A2 — Analog In / Capacitive Touch / PWM | — | analog-input, digital-input, digital-output, pwm | | PA04 | A3 — Analog In / Capacitive Touch / PWM | — | analog-input, digital-input, digital-output, pwm | | PA05 | A4/SCL — Analog In / Capacitive Touch | — | analog-input, digital-input, digital-output | | PB02 | A5/SDA — Analog In / Capacitive Touch | — | analog-input, digital-input, digital-output | | PA20 | A6/TX — Analog In / UART TX / Capacitive Touch | UART | analog-input, digital-input, digital-output | | PA07 | A7/RX — Analog In / UART RX / Capacitive Touch | UART | analog-input, digital-input, digital-output | ## Description ## Overview The Circuit Playground Express is Adafruit's upgraded educational board, replacing the Classic's ATmega32u4 with the ATSAMD21 ARM Cortex-M0+ running at 48 MHz. The upgrade brings significantly more compute power, 2MB of SPI flash for storing CircuitPython scripts and libraries, and full support for Microsoft MakeCode's drag-and-drop visual programming environment. The board packs a complete sensor suite: a LIS3DH triple-axis accelerometer with tap and free-fall detection, a MEMS microphone, a phototransistor (light and color sensing), a thermistor, and both infrared transmitter and receiver for remote control and inter-board communication. Ten addressable mini NeoPixels ring the board, and a 7.5mm magnetic speaker with a class D amplifier provides audio output with true analog sound. Eight alligator-clip friendly pads support capacitive touch and analog input, making this ideal for craft and wearable projects where alligators connect to fruit, foil, or conductive materials. Two push buttons (A and B), one slide switch, and a reset button complete the input options. Unlike the Classic, the Express supports CircuitPython, MakeCode, Arduino IDE, and code.org CS Discoveries — making it suitable for beginners all the way to experienced developers. The ARM Cortex-M0+ enables more complex projects, particularly audio manipulation and multi-sensor data fusion that would overwhelm an 8-bit AVR. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3333&ref=openhardware.directory&product=circuit-playground-express&source=md-export) — 24.95 ## Resources - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F3333&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fadafruit%2FAdafruit-Circuit-Playground-Express-PCB&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fadafruit-circuit-playground-express%2Foverview&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fimages%2Fproduct-files%2F2772%2Fatmel-42181-sam-d21_datasheet.pdf&ref=openhardware.directory&product=circuit-playground-express&source=md-export) - [schematics](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-learn.adafruit.com%2Fassets%2Fassets%2F000%2F049%2F671%2Fmedium800%2Fmakecode_schem.png&ref=openhardware.directory&product=circuit-playground-express&source=md-export) ## Tags `circuit-playground`, `atsamd21`, `neopixel`, `educational`, `circuitpython`, `makecode`, `capacitive-touch`, `ir`, `adafruit` ## Images ![Circuit Playground Express](https://nbg1.your-objectstorage.com/openhardware-directory/entities/circuit-playground-express/767ae3dd027e.jpg) --- [View full device page](https://openhardware.directory/devices/circuit-playground-express)