M5Stack CardKB2 Keyboard Unit ESP32-C61

The CardKB2 Unit is a card format keyboard from M5Stack with 42 keys and an ESP32-C61HF4 as a controller. The RISC-V single-core processor with 120 MHz brings 4 MB flash and supports 2.4 GHz Wi-Fi 6 as well as Bluetooth LE. The keyboard supports four operating modes switchable by key combination: I2C (factory setting), UART, BLE HID, and ESP-NOW. In BLE-HID mode, the CardKB2 registers as a wireless Bluetooth keyboard on a smartphone, tablet, or PC. In ESP-NOW mode, it sends keystrokes as a broadcast to other ESP32 devices. The selected mode remains stored even after a power failure. Special characters and function keys are accessible via the Sym and Fn layers; the Aa button offers one-shot caps, caps lock, and other functions. An RGB LED indicates the active mode and keyboard status. The unit connects via the Grove port (I2C or UART) to the M5Stack controller or via USB-C, which also serves for flashing the firmware. The input is protected with an overvoltage protection, and reserved M2 mounting holes facilitate mechanical installation. With a footprint of only 84.7 × 54.3 mm, the keyboard is ideal as an input device for portable devices, embedded systems, and IoT control terminals.

Features:

• Keyboard with 42 keys in card format offers full text input including Sym and Fn layers for special characters
• ESP32-C61HF4 with RISC-V core, 120 MHz, 4 MB flash, Wi-Fi 6, and Bluetooth LE controls the unit
• Operating modes I2C, UART, BLE HID, and ESP-NOW are switchable by key combination and remain stored
• BLE-HID mode turns the unit into a wireless Bluetooth keyboard for smartphones, tablets, and PCs
• RGB LED indicates the active mode as well as caps lock and function states
• Grove port and USB-C with overvoltage protection and M2 mounting holes facilitate connection and installation

Application Examples:

• Text input for M5Stack Core devices and other microcontroller projects via the Grove port
• Wireless mini keyboard for smartphones, tablets, or single-board computers in BLE-HID mode
• Control terminal for IoT and embedded systems in control and automation projects
• Remote control of other ESP32 devices via ESP-NOW broadcast
• Compact input device for training and educational projects

Documentation:

• M5Stack Wiki
• Official M5Stack Forum

Technical Specifications:

• Manufacturer: M5Stack
• Manufacturer SKU: U215
• EAN: 6972934176400
• SoC: ESP32-C61HF4, RISC-V single-core, 120 MHz
• Memory: 4 MB flash
• Connectivity: 2.4 GHz Wi-Fi 6 (802.11ax), Bluetooth LE
• Keys: 42 keys, plus reset and boot key
• Operating Modes: I2C (factory setting), UART, BLE HID, ESP-NOW
• Interfaces: 1× Grove port (HY2.0-4P, I2C/UART), 1× USB-C
• Grove Pin Assignment: GND, 5V, SDA/UART_RX (G26), SCL/UART_TX (G25)
• Status LED: 1× RGB LED (XL-1615RGBC-RF)
• Supply Voltage: DC 5 V (USB-C or Grove), with overvoltage protection
• Current Consumption: 19.31 mA @ 5 V (standby)
• Mounting: Reserved M2 mounting holes
• Product Dimensions: 84.7 × 54.3 × 1.0 mm
• Product Weight: 22.4 g
• Package Dimensions: 140 × 90 × 6 mm
• Gross Weight: 29 g

Package Contents:

• 1× CardKB2 Keyboard Unit
• 1× Grove Cable (HY2.0-4P, 20 cm)