M5Stack CardKB v1.1 I2C Mini Keyboard Unit (ATMega8A)

Description

M5Stack CardKB v1.1 is a card-sized QWERTY 50-key PCB matrix keyboard unit for compact text input in embedded projects. The Unit CardKB v1.1 uses an ATMega8A encoding MCU and outputs key values over I2C, so it works as an I2C mini keyboard for M5Stack Core and compatible host controllers. With the HY2.0-4P Grove interface, an onboard RGB status LED, Shift/Sym/Fn key modes, and Arduino/UIFlow support, M5Stack CardKB v1.1 helps M5Stack projects add physical keyboard input without a full-size USB keyboard.

This ATMega8A keyboard module is especially suitable for menu navigation, quick parameter entry, serial-console style input, portable controllers, and handheld IoT terminals. Unit CardKB v1.1 communicates through I2C address 0x5F, making the I2C mini keyboard easy to poll from supported firmware while keeping wiring simple through the 4-pin M5Stack Port.A connection.

Compared with a generic keypad, M5Stack CardKB v1.1 provides a compact QWERTY layout, symbol input, uppercase input, custom Fn key output, and documented key-code mapping. For developers building a small control panel or M5Stack Core accessory, the I2C mini keyboard design keeps keyboard scanning inside the unit and sends ready-to-use key values to the host.

Features

• M5Stack CardKB v1.1 form factor: card-sized keyboard unit with an 88.0 x 54.0 x 5.0 mm body for compact embedded interfaces.
• QWERTY 50-key input: full keyboard input with multiple key combinations for letters, symbols, arrows, enter, backspace, and function output.
• ATMega8A keyboard encoder: uses an ATMega8A as the encoding MCU, reducing the host workload for matrix-keyboard scanning.
• I2C mini keyboard output: communicates over I2C at address 0x5F, returning key values that the host can read directly.
• HY2.0-4P Grove interface: connects through the M5Stack Port.A wiring layout for GND, 5V, SDA, and SCL.
• RGB status LED: one onboard RGB LED indicates keyboard status for Shift, Sym, and Fn modes.
• Arduino and UIFlow support: Unit CardKB v1.1 has official Arduino, UIFlow1, and UIFlow2 development resources.
• Custom Fn mode: M5Stack CardKB v1.1 can output a third key value for custom function-key behavior.
• Embedded I2C mini keyboard use: the unit is made for compact host devices that need reliable physical text input.

Specifications

Applications

• Keyboard peripheral for M5Stack Core: M5Stack CardKB v1.1 is suitable for adding local text input to M5Stack Core projects.
• Compact embedded control panels: use the I2C mini keyboard for menu navigation, setting values, and confirming commands.
• Portable IoT terminals: Unit CardKB v1.1 helps handheld devices accept direct user input without a large external keyboard.
• Arduino and UIFlow prototypes: the ATMega8A-based keyboard is useful for quick interface experiments with official M5Stack software resources.
• Serial-console style input: the I2C mini keyboard can be used where host firmware reads key codes and displays or transmits user commands.
• Small device text entry: the I2C mini keyboard fits compact products that still require letters, symbols, and function-key input.

Product List

Other Content

Key Operation

Unit CardKB v1.1 outputs different key values depending on normal, Sym, Shift, and Fn operation. This makes M5Stack CardKB v1.1 more flexible than a simple numeric keypad while keeping the host-side code straightforward.

• Single key: the keyboard outputs the first key value; letter keys output lowercase characters.
• Sym + key: the keyboard outputs the second key value; double-click Sym to lock symbol mode and double-click again to unlock.
• Shift + key: the keyboard outputs uppercase letters; double-click Shift to lock uppercase mode and double-click again to unlock.
• Fn + key: the keyboard outputs the third key value for custom function-key behavior.

PinMap

I2C Information

For I2C mini keyboard integration, the host polls the keyboard address and receives a key value or 0x00 when no key is pressed.

ATMega8A ISP Download Interface

The official M5Stack CardKB v1.1 documentation provides an ISP download pin definition for advanced firmware work on the ATMega8A controller.

Model Size

The Unit CardKB v1.1 board size is 88.0 x 54.0 x 5.0 mm. The official model size PDF is included in Resources for mechanical integration and enclosure planning.

Resources

• M5Stack Unit CardKB v1.1 Documentation
• Unit CardKB v1.1 Model Size PDF
• Unit CardKB v1.1 Arduino Example with M5Core
• Unit CardKB UIFlow1 Docs
• CardKB Unit UIFlow2 Programming Guide
• Unit CardKB v1.1 Internal Firmware
• Unit CardKB v1.1 Communication Protocol and User Manual

FAQ

Is M5Stack CardKB v1.1 a standalone computer keyboard?

No. M5Stack CardKB v1.1 is an embedded keyboard unit. It is designed to connect to a host controller through I2C, and the host reads key values from the I2C mini keyboard.

Which host is this keyboard designed for?

The official application is keyboard peripheral use with M5Stack Core. Unit CardKB v1.1 can also be used with compatible I2C host hardware when the wiring and firmware support the 0x5F I2C address.

Does Unit CardKB v1.1 support Arduino and UIFlow?

Yes. The official resources include Arduino example code, UIFlow1 documentation, and UIFlow2 documentation for the Unit CardKB v1.1.

What does the ATMega8A do in this keyboard?

The ATMega8A works as the encoding MCU. This keyboard controller handles the key matrix and lets the host read key values through I2C instead of scanning all keys directly.

How do Shift, Sym, and Fn work?

Shift changes letter output to uppercase, Sym outputs symbol values, and Fn provides custom function-key output. These modes make M5Stack CardKB v1.1 a flexible I2C mini keyboard for compact device interfaces.

Can the internal firmware be modified?

M5Stack provides internal firmware resources and an ISP download interface reference for advanced users. Firmware work should be handled carefully because the ATMega8A controller is part of the input system.