# DFRobot Beetle CM-32U4

> Ultra-compact Arduino Leonardo-compatible microcontroller board with ATmega32U4, integrated lithium battery charging, and native USB in a tiny 22x20.5mm form factor.

## Quick Facts

- **Brand:** DFRobot
- **Price:** ~$8.9
- **Product Readiness:** Consumer Ready
- **CPU:** AVR 8-bit single-core @ 16MHz
- **CPU Architecture:** AVR 8-bit
- **CPU Cores:** 1
- **RAM:** 2.5KB SRAM
- **Flash:** 32KB
- **USB:** Micro-USB (native USB 2.0 Full-speed)
- **Power:** 5V USB / LiPo battery (BAT pin) / 5V external (VIN)
- **Operating Voltage:** 5V
- **Operating Temp:** -40°C to 125°C
- **Dimensions:** 22 × 20.5mm
- **Weight:** 16.5g
- **Battery:** LiPo (user-supplied, 1.25mm JST)
- **Antenna:** N/A

## Use Cases

- usb-hid-device
- e-textiles
- compact-iot-node
- wearable

## Components

- **ATmega32U4** (mcu): Microchip ATmega32U4 running at 16MHz with 32KB flash, 2.5KB SRAM, 1KB EEPROM, native USB 2.0 Full-speed device, 12-channel 10-bit ADC, and JTAG debug interface. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2Fdevicedoc%2Fatmel-7766-8-bit-avr-atmega16u4-32u4_datasheet.pdf&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)
- **TP4056X** (battery-charger): Linear lithium battery charger with programmable charge current of 200-600mA and thermal regulation for safe LiPo charging. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fdlnmh9ip6v2uc.cloudfront.net%2Fdatasheets%2FPrototyping%2FTP4056.pdf&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)

## Protocols

- **SPI** (SPI0): MOSI: MOSI, MISO: MISO, SCK: SCK
- **I2C** (I2C0): SDA: D1, SCL: D0
- **UART** (Serial1): TX: D1, RX: D0

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| D0 | UART RX / I2C SCL | UART/I2C | digital-input, digital-output |
| D1 | UART TX / I2C SDA | UART/I2C | digital-input, digital-output |
| D9 | Digital / PWM / Analog (A9) | GPIO | digital-input, digital-output, pwm, adc |
| D10 | Digital / PWM / Analog (A10) | GPIO | digital-input, digital-output, pwm, adc |
| D11 | Digital / PWM | GPIO | digital-input, digital-output, pwm |
| A0 | Analog Input | ADC | digital-input, digital-output, adc |
| A1 | Analog Input | ADC | digital-input, digital-output, adc |
| A2 | Analog Input | ADC | digital-input, digital-output, adc |
| MOSI | SPI MOSI | SPI | digital-input, digital-output |
| MISO | SPI MISO | SPI | digital-input, digital-output |
| SCK | SPI Clock | SPI | digital-input, digital-output |

## Description

## Overview

The DFRobot Beetle CM-32U4 is an upgraded version of the original Beetle board, packing an ATmega32U4 microcontroller with integrated lithium battery charge management into a remarkably small 22x20.5mm footprint. Fully compatible with Arduino Leonardo, it can be programmed directly from the Arduino IDE without any additional drivers or board packages.

Despite its tiny size, the Beetle CM-32U4 exposes the most commonly used communication interfaces including I2C, SPI, UART, two analog inputs, and two digital I/O pins. The onboard TP4056X charging IC supports 200-600mA charge current for LiPo batteries, making it ideal for battery-powered portable projects.

The board's coin-sized form factor and native USB capability make it particularly well-suited for e-textiles, wearable electronics, USB HID devices like custom keyboards and macro pads, and any project where space is at a premium. Three flexible power options — USB, battery pack via BAT pin, or 5V external via VIN — give builders maximum flexibility for deployment in tight spaces.

## Where to Buy

- [DFRobot](https://openhardware.directory/r?to=https%3A%2F%2Fwww.dfrobot.com%2Fproduct-2475.html&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export) — $8.90

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.dfrobot.com%2Fproduct-2475.html&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Fwiki.dfrobot.com%2FBeetle_CM_32U4_SKU_DFR0816&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)
- [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2Fdevicedoc%2Fatmel-7766-8-bit-avr-atmega16u4-32u4_datasheet.pdf&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)
- [schematics](https://openhardware.directory/r?to=https%3A%2F%2Fdfimg.dfrobot.com%2Fnobody%2Fwiki%2Fca0e40f37bf29ee0d43170b1cb62aba1.PDF&ref=openhardware.directory&product=dfrobot-beetle-cm-32u4&source=md-export)

## Images

![DFRobot Beetle CM-32U4](https://nbg1.your-objectstorage.com/openhardware-directory/entities/dfrobot-beetle-cm-32u4/d8f44be2275f.jpg)
![DFRobot Beetle CM-32U4](https://nbg1.your-objectstorage.com/openhardware-directory/entities/dfrobot-beetle-cm-32u4/35a3d2ebe4c6.jpg)
![DFRobot Beetle CM-32U4](https://nbg1.your-objectstorage.com/openhardware-directory/entities/dfrobot-beetle-cm-32u4/bcbb1cbf76c8.jpg)
![DFRobot Beetle CM-32U4](https://nbg1.your-objectstorage.com/openhardware-directory/entities/dfrobot-beetle-cm-32u4/c358986e0068.jpg)
![DFRobot Beetle CM-32U4](https://nbg1.your-objectstorage.com/openhardware-directory/entities/dfrobot-beetle-cm-32u4/fdc96749bcc1.jpg)

> **Battery Powered:** Li-Po

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