Description The M5Stack CardKB2 is a card-sized 42-key keyboard unit for portable text input, embedded HMI control and wireless interaction. It is built around the ESP32-C61HF4 and supports 2.4GHz Wi-Fi 6 plus BLE wireless communication. The preloaded firmware lets this ESP32-C61 keyboard work through I2C, UART, BLE HID or ESP-NOW. It includes an HY2.0-4P expansion interface, a USB Type-C port for power and firmware flashing, an RGB status LED, Reset and Boot buttons, and built-in input overvoltage protection. Features ESP32-C61HF4 controller with 4MB Flash and 2.4GHz Wi-Fi 6 support. 42-key keyboard input with single press, Sym and Fn key combinations. Four communication modes: I2C, UART, BLE HID and ESP-NOW. HY2.0-4P expansion interface for I2C/UART communication. USB Type-C port for power supply and firmware flashing. RGB LED status indicator, Reset button and Boot button. Built-in input overvoltage protection and reserved M2 mounting holes. Specifications Specification Parameter SoC ESP32-C61HF4, RISC-V 32-bit single-core processor, 120 MHz Flash 4MB Wireless 2.4GHz Wi-Fi 6, BLE Keys 42-key keyboard, 1x Reset button, 1x Boot button USB Type-C Power supply and firmware flashing, default firmware log output 115200bps @ 8N1 RGB LED 1x RGB LED Expansion Interface 1x HY2.0-4P Standby Power [email protected] powered via Grove interface Product Size 84.7 x 54.3 x 1.0mm Product Weight 22.4g Package Size 170.0 x 120.0 x 8.0mm Gross Weight 28.9g Applications Text input for portable devices. Human-machine interaction in embedded systems. Wireless control terminals for IoT devices. Educational programming and maker projects. Compact BLE HID keyboard control for phones, tablets or computers. Product List 1 x Unit CardKB2 1 x HY2.0-4P Grove Cable (20cm) Other Content Key Operation The Aa key supports one-shot uppercase, caps lock and hold-to-uppercase behavior. The Sym key toggles symbol input, and the Fn key enables mode switching and combined functions with the red indicator LED. Mode Switching Hold Fn + Sym and press 1, 2, 3 or 4 to select I2C, UART, ESP-NOW or BLE HID mode. The selected mode is saved automatically and remains active after power cycling. BLE HID Use In BLE HID mode, Fn + 1 outputs Esc, while Fn + D, X, Z and C output cursor up, down, left and right. During pairing, the device appears as CardKB2-xxxx, where xxxx represents the last four digits of the MAC address. Resources CardKB2 Keyboard Unit Product Documentation CardKB2 Arduino Tutorial Unit CardKB2 User Manual and Registers Unit CardKB2 Schematics PDF Unit CardKB2 Dimension Diagram PDF ESP32-C61HF4 Datasheet Unit CardKB2 Arduino Library Unit CardKB2 Internal Firmware FAQ What communication modes does CardKB2 support? It supports I2C, UART, BLE HID and ESP-NOW, selected through Fn + Sym plus the number keys. Can it work as a wireless keyboard? Yes. In BLE HID mode, it can pair with BLE HID-compatible phones, tablets and computers as a wireless keyboard. How is the keyboard unit powered? It can be powered through USB Type-C or DC 5V, and the documented standby current is [email protected] when powered via the Grove interface. Which connector is used for wired host communication? The onboard HY2.0-4P connector provides I2C/UART communication with a host device. What is included in the package? The package includes one Unit CardKB2 and one HY2.0-4P Grove Cable measuring 20cm. What projects is this keyboard unit suited for? It is suited for portable input, embedded HMI control, IoT wireless terminals, education and maker projects.
