Chain Switch

SwitchChain is the helper class for switch devices on the Chain bus. It provides methods to read ADC values (12-bit and 8-bit), configure switch thresholds, set slip mode, and monitor switch status changes.

Support the following products:

UiFlow2 Example

Switch status monitoring

Open the m5core_chain_switch_basic_example.m5f2 project in UiFlow2.

This example demonstrates how to read ADC values and switch status from the Chain Switch sensor and display them on screen. It registers open/close trigger callbacks and updates the status label when the switch state changes.

UiFlow2 Code Block:

Example output:

None

MicroPython Example

Switch status monitoring

This example demonstrates how to read ADC values and switch status from the Chain Switch sensor and display them on screen. It registers open/close trigger callbacks and updates the status label when the switch state changes.

MicroPython Code Block:

# SPDX-FileCopyrightText: 2026 M5Stack Technology CO LTD
#
# SPDX-License-Identifier: MIT

import os, sys, io
import M5
from M5 import *
from chain import SwitchChain
from chain import ChainBus


title0 = None
label_adc = None
label_state = None
bus2 = None
chain_switch_0 = None


def chain_switch_0_open_event(args):
    global title0, label_adc, label_state, bus2, chain_switch_0
    label_state.setText(str("State: Open"))


def chain_switch_0_close_event(args):
    global title0, label_adc, label_state, bus2, chain_switch_0
    label_state.setText(str("State: Close"))


def setup():
    global title0, label_adc, label_state, bus2, chain_switch_0

    M5.begin()
    Widgets.setRotation(1)
    Widgets.fillScreen(0x000000)
    title0 = Widgets.Title("Chain Switch Example", 3, 0xFFFFFF, 0x0000FF, Widgets.FONTS.DejaVu24)
    label_adc = Widgets.Label("ADC: --", 20, 70, 1.0, 0xFFFFFF, 0x000000, Widgets.FONTS.DejaVu24)
    label_state = Widgets.Label(
        "State: --", 20, 113, 1.0, 0xFFFFFF, 0x000000, Widgets.FONTS.DejaVu24
    )

    bus2 = ChainBus(2, tx=21, rx=22)
    chain_switch_0 = SwitchChain(bus2, 1)
    chain_switch_0.set_trigger_callback(SwitchChain.STATUS_OPEN, chain_switch_0_open_event)
    chain_switch_0.set_trigger_callback(SwitchChain.STATUS_CLOSE, chain_switch_0_close_event)
    chain_switch_0.set_trigger(True)
    if chain_switch_0.get_switch_status():
        label_state.setText(str("State: Open"))
    else:
        label_state.setText(str("State: Close"))


def loop():
    global title0, label_adc, label_state, bus2, chain_switch_0
    M5.update()
    label_adc.setText(str((str("ADC: ") + str((chain_switch_0.get_adc12())))))


if __name__ == "__main__":
    try:
        setup()
        while True:
            loop()
    except (Exception, KeyboardInterrupt) as e:
        try:
            bus2.deinit()
            from utility import print_error_msg

            print_error_msg(e)
        except ImportError:
            print("please update to latest firmware")

Example output:

None

API

SwitchChain

class chain.switch.SwitchChain(bus, device_id)

Bases: KeyChain

Switch Chain class for interacting with switch devices over Chain bus.

Parameters:

bus (ChainBus) – The Chain bus instance.
device_id (int) – The device ID of the switch on the Chain bus.

UiFlow2 Code Block:

MicroPython Code Block:

from chain import ChainBus
from chain import SwitchChain

bus2 = ChainBus(2, tx=21, rx=22)
chain_switch_0 = SwitchChain(bus2, 1)

For other button and some general methods, please refer to the ChainKey class.

get_adc12()

Get the 12-bit ADC value of the switch.

Returns:: 12-bit ADC value (0-4095), or None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

value = chain_switch_0.get_adc12()

get_adc8()

Get the 8-bit ADC value of the switch.

Returns:: 8-bit ADC value (0-255), or None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

value = chain_switch_0.get_adc8()

set_slip_mode(mode, save=False)

Set the slider change mode.

Parameters:

mode (int) – Slider change mode. Use SwitchChain.SLIP_MODE_DOWNUP_DEC (0) for decreasing or SwitchChain.SLIP_MODE_DOWNUP_INC (1) for increasing.
save (bool) – Whether to save the setting to flash. Default: False.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_switch_0.set_slip_mode(SwitchChain.SLIP_MODE_DOWNUP_INC, True)

get_slip_mode()

Get the slider change mode.

Returns:: Slider change mode. SwitchChain.SLIP_MODE_DOWNUP_DEC (0) for decreasing or SwitchChain.SLIP_MODE_DOWNUP_INC (1) for increasing. Returns None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

mode = chain_switch_0.get_slip_mode()

set_switch_thresh(open_threshold, close_threshold, save=False)

Set the switch open and close thresholds.

Parameters:

open_threshold (int) – Open threshold value (0-4095). Must be greater than close_threshold.
close_threshold (int) – Close threshold value (0-4095). Must be less than open_threshold.
save (bool) – Whether to save the threshold to flash. Default: False.

Returns:

True if the operation was successful, False otherwise.

Return type:

bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_switch_0.set_switch_thresh(3000, 1000, True)

get_open_thresh()

Get the switch open threshold.

Returns:: Open threshold value (0-4095), or None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

open_th = chain_switch_0.get_open_thresh()

get_close_thresh()

Get the switch close threshold.

Returns:: Close threshold value (0-4095), or None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

close_th = chain_switch_0.get_close_thresh()

get_switch_status()

Get the switch status.

Returns:: Switch status. 0 means close, 1 means open. Returns None if failed.
Return type:: int

UiFlow2 Code Block:

MicroPython Code Block:

status = chain_switch_0.get_switch_status()

set_trigger(enable)

Enable or disable status change reporting.

Parameters:: enable (bool) – True to enable status change reporting, False to disable it.
Returns:: True if the operation was successful, False otherwise.
Return type:: bool

UiFlow2 Code Block:

MicroPython Code Block:

success = chain_switch_0.set_trigger(True)

get_trigger()

Get whether status change reporting is enabled.

Returns:: True if status change reporting is enabled, False if disabled. Returns False if failed.
Return type:: bool

UiFlow2 Code Block:

MicroPython Code Block:

enabled = chain_switch_0.get_trigger()

set_trigger_callback(trigger_type, callback)

Set callback for switch status change events.

Parameters:

trigger_type (int) – Trigger type to listen for. Use SwitchChain.STATUS_CLOSE (0) or SwitchChain.STATUS_OPEN (1).
callback – Callback function that will be called when switch status changes.

Return type:

None

Note

Chain related methods cannot be called in the callback function.

UiFlow2 Code Block:

MicroPython Code Block:

def switch_status_callback():
    print("Switch opened")

# Listen for open status only
chain_switch_0.set_trigger_callback(SwitchChain.STATUS_OPEN, switch_status_callback)

# Listen for close status only
chain_switch_0.set_trigger_callback(SwitchChain.STATUS_CLOSE, switch_status_callback)