Chain Key

Chain Key is a key module that can be connected to the M5Chain series devices. This module provides functions to read the key states.

Support the following products:

Chain Key

UiFlow2 Example

USB Keyboard

Open the chain_key_usb_keyboard_example.m5f2 project in UiFlow2.

This example demonstrates how to use the Chain Key as a USB keyboard.

UiFlow2 Code Block:

chain_key_usb_keyboard_example.png

Example output:

None

MicroPython Example

USB Keyboard

This example demonstrates how to use the Chain Key as a USB keyboard.

MicroPython Code Block:

 1# SPDX-FileCopyrightText: 2025 M5Stack Technology CO LTD
 2#
 3# SPDX-License-Identifier: MIT
 4
 5import os, sys, io
 6import M5
 7from M5 import *
 8from chain import KeyChain
 9from chain import ChainBus
10from usb.device.keyboard import Keyboard
11from usb.device.hid import KeyCode
12
13
14bus2 = None
15keyboard = None
16chain_key_0 = None
17
18
19key_press = None
20
21
22def chain_key_0_click_event(args):
23    global bus2, keyboard, chain_key_0, key_press
24    key_press = True
25
26
27def setup():
28    global bus2, keyboard, chain_key_0, key_press
29
30    M5.begin()
31    bus2 = ChainBus(2, tx=6, rx=5)
32    keyboard = Keyboard()
33    chain_key_0 = KeyChain(bus2, 1)
34    chain_key_0.set_click_callback(chain_key_0_click_event)
35    key_press = False
36
37
38def loop():
39    global bus2, keyboard, chain_key_0, key_press
40    M5.update()
41    if keyboard.is_open():
42        if key_press:
43            keyboard.input(KeyCode.A)
44            key_press = False
45
46
47if __name__ == "__main__":
48    try:
49        setup()
50        while True:
51            loop()
52    except (Exception, KeyboardInterrupt) as e:
53        try:
54            from utility import print_error_msg
55
56            print_error_msg(e)
57        except ImportError:
58            print("please update to latest firmware")

Example output:

None

API

KeyChain

class chain.key.KeyChain(bus, device_id)

Bases: object

Create a KeyChain object.

Parameters:

  • bus (ChainBus) – ChainBus object.

  • device_id (int) – Device ID.

UiFlow2 Code Block:

init.png

MicroPython Code Block:

from chain import ChainBus
from chain import KeyChain

chainbus_0 = ChainBus(2, 32, 33, verbose=True)
keychain_0 = KeyChain(chainbus_0, 1)
MODE_POLL = 0

Button Polling mode

MODE_EVENT = 1

Button Event mode

get_button_state()

get button state.

Returns:

Button state, True if pressed, False otherwise.

Return type:

bool

UiFlow2 Code Block:

get_button_state.png

MicroPython Code Block:

keychain_0.get_button_state()
set_click_callback(callback)

set button click callback.

Parameters:

callback – Callback function.

Return type:

None

Note

Chain related methods cannot be called in the callback function.

UiFlow2 Code Block:

key_click_callback.png

MicroPython Code Block:

def keychain_0_click_callback(args):
    print("click")

keychain_0.set_click_callback(keychain_0_click_callback)
set_double_click_callback(callback)

set button double click callback.

Parameters:

callback – Callback function.

Return type:

None

Note

Chain related methods cannot be called in the callback function.

UiFlow2 Code Block:

double_click_callback.png

MicroPython Code Block:

def keychain_0_double_click_callback(args):
    print("double click")

keychain_0.set_double_click_callback(keychain_0_double_click_callback)
set_long_press_callback(callback)

set button long press callback.

Parameters:

callback – Callback function.

Return type:

None

Note

Chain related methods cannot be called in the callback function.

UiFlow2 Code Block:

long_press_callback.png

MicroPython Code Block:

def keychain_0_long_press_callback(args):
    print("long press")

keychain_0.set_long_press_callback(keychain_0_long_press_callback)
set_button_double_click_trigger_interval(interval_ms)

set button double click trigger interval.

Parameters:

interval_ms (int) – Interval time in milliseconds. range: 100-1000

Returns:

True if success, False otherwise.

Return type:

bool

UiFlow2 Code Block:

set_button_double_click_trigger_interval.png

MicroPython Code Block:

keychain_0.set_button_double_click_trigger_interval(100)
set_button_long_press_trigger_interval(interval_ms)

set button long press trigger interval.

Parameters:

interval_ms (int) – Interval time in milliseconds. range: 3000-30000

Returns:

True if success, False otherwise.

Return type:

bool

UiFlow2 Code Block:

set_button_long_press_trigger_interval.png

MicroPython Code Block:

keychain_0.set_button_long_press_trigger_interval(3000)
get_button_double_click_trigger_interval()

get button double click trigger interval.

Returns:

Interval time in milliseconds.

Return type:

int

UiFlow2 Code Block:

get_button_double_click_trigger_interval.png

MicroPython Code Block:

interval = keychain_0.get_button_double_click_trigger_interval()
get_button_long_press_trigger_interval()

get button long press trigger interval.

Returns:

Interval time in milliseconds.

Return type:

int

UiFlow2 Code Block:

get_button_long_press_trigger_interval.png

MicroPython Code Block:

interval = keychain_0.get_button_long_press_trigger_interval()
set_button_mode(mode)

set button mode.

Parameters:

mode (int) – Button mode. Use KeyChain.MODE_POLL or KeyChain.MODE_EVENT.

Returns:

True if success, False otherwise.

Return type:

bool

UiFlow2 Code Block:

set_button_mode.png

MicroPython Code Block:

keychain_0.set_button_mode(KeyChain.MODE_EVENT)
get_button_mode()

get button mode.

Returns:

Button mode. KeyChain.MODE_POLL or KeyChain.MODE_EVENT.

Return type:

int

UiFlow2 Code Block:

get_button_mode.png

MicroPython Code Block:

mode = keychain_0.get_button_mode()
set_rgb_color(color)

set RGB color.

Parameters:

color (int) – RGB color value.

Returns:

True if success, False otherwise.

Return type:

bool

UiFlow2 Code Block:

set_rgb_color.png

MicroPython Code Block:

keychain_0.set_rgb_color(0xFF0000)
get_rgb_color()

get RGB color.

Parameters:

index – Index of the RGB LED.

Returns:

RGB color value.

Return type:

int

UiFlow2 Code Block:

get_rgb_color.png

MicroPython Code Block:

color = keychain_0.get_rgb_color()
set_rgb_brightness(brightness, save=False)

set RGB brightness.

Parameters:

  • brightness (int) – Brightness value (0-100).

  • save (bool) – Whether to save the brightness setting to flash.

Returns:

True if success, False otherwise.

Return type:

bool

UiFlow2 Code Block:

set_rgb_brightness.png

MicroPython Code Block:

keychain_0.set_rgb_brightness(80)
get_rgb_brightness()

get RGB brightness.

Returns:

Brightness value (0-100).

Return type:

int

UiFlow2 Code Block:

get_rgb_brightness.png

MicroPython Code Block:

brightness = keychain_0.get_rgb_brightness()
get_bootloader_version()

get bootloader version.

Returns:

Bootloader version.

Return type:

int

UiFlow2 Code Block:

get_bootloader_version.png

MicroPython Code Block:

version = keychain_0.get_bootloader_version()
get_firmware_version()

get firmware version.

Returns:

Firmware version.

Return type:

int

UiFlow2 Code Block:

get_firmware_version.png

MicroPython Code Block:

version = keychain_0.get_firmware_version()
get_device_uid(uid_type)

get device UID.

Parameters:

uid_type (int) – UID type, 0 for 4-byte UID, 1 for 12-byte UID.

Returns:

Tuple of UID bytes (4 bytes or 12 bytes). Returns empty tuple on error.

Return type:

tuple

UiFlow2 Code Block:

get_device_uid.png

MicroPython Code Block:

uid = keychain_0.get_device_uid(0)  # 4-byte UID
uid = keychain_0.get_device_uid(1)  # 12-byte UID