Earykong TYMC-1 Door Window Contact Sensor (MC400A)
Earykong TYMC-1 Door Window

Available from:

Install method:
USB to Serial

GPIO #Component
GPIO00 None
GPIO01 Tuya Tx
GPIO02 None
GPIO03 Tuya Rx
GPIO04 None
GPIO05 None
GPIO09 None
GPIO10 None
GPIO12 None
GPIO13 None
GPIO14 None
GPIO15 None
GPIO16 None
Configuration (old format, will be converted to new template when applied)

Unsupported Hardware

Sadly, new versions of this sensor come with an unsupported XR4 module

Old Hardware Version Instructions

Found listed also as MC400A under various brand names.

Please read TuyaMCU article to understand the terminology and configuration process.

This is a Tuya/Smart Life battery powered contact (door or window) sensor. Runs on two AAA batteries (not supplied with the device).

Identified with MCU Product ID: {"p":"hx5ztlztij4yxxvg","v":"1.0.0"} which is also printed on the TYWE3S module.

Packaging image


To have best results with this type of device I strongly recommend compiling a stripped down binary. There’s an unofficial binary, compiled from current development release. Flash at your own risk.

Example user_config_override defines (for Tasmota 8.2+).


Easily disassembled by removing the back plate, unscrewing the screw in the battery holder and prying away the plastic using the bottom slot. Disassembly

The PCB has only the 20191022 marking on it and a prominent TYWE3S module with the product ID printed. There are broken out pins for 3v3, RX, TX and GND but to be able to solder a pin header in them you need to desolder the battery holder which is probably not worth the trouble since all the pins are accessible on the TYWE3S.


MCU details

STC8F1K08S2 MCU, situated on the left of the broken out pins, powers on the Tuya module on reed actuation or on “Reset” bottom button press for a short amount of time sufficient to send opening or closing message.

Reset Button

MCU PIN Connection explanation
P5.4 D2 LED
P5.5 SC9JF controls ESP power via EN pin on voltage regulator
P3.3 R12 RESET button
P3.2 S1 reed switch
P3.1 RX ESP and broken out pin
P3.0 TX ESP and broken out pin

Due to this design it is somewhat difficult to tuya-convert or even configure the device compared to non-battery powered ones. I flashed the device over serial powering the TYWE3S from the USB-to-serial adapter.


If you’re using battery power you need to prevent the device from going to sleep by actuating the reed switch constantly (approximately every 5 seconds) during the configuration or use the serial message.

You can use

SerialSend5 55AA000200010002

shortly after boot to put the device into wi-fi search mode (rapidly blinking red LED) which will keep it powered on for around 60 seconds.

Change device to a TuyaMCU module (or apply the provided template, result is the same)

Module 54

Disable multipress button options to prevent a device reset or Wi-Fi AP config mode, disable Power Cycle recovery, turn on TuyaReceived publish to MQTT and set switchmode to follow instead of toggle

Backlog SetOption1 1; SetOption65 1; SetOption66 1; SwitchMode 1

Switch the device to battery powered sensor mode (fnId 51):

TuyaMCU 51,21

Check with TuyaMCU for the following configuration:



dpID 1 reed switch: closed = off / open = on
dpID 3 battery power: 0 = low / 1 = medium / 2 = high

The button labelled reset can wake up the device with a short press or put it into Wi-Fi config mode on long press.

dpID 1 is assigned to Relay1 by default.

There is no function in Tasmota for enum dpID’s currently so we will use a rule to report battery status (high, medium or low) to a custom topic (change it to any other topic suitable for you)

Rule1 ON TuyaReceived#Data=55AA00050005030400010213 DO publish2 stat/%topic%/BATT high ENDON ON TuyaReceived#Data=55AA00050005030400010112 DO publish2 stat/%topic%/BATT medium ENDON ON TuyaReceived#Data=55AA00050005030400010011 DO publish2 stat/%topic%/BATT low ENDON

UPDATED: Actual State on/off

Rule2 ON TuyaReceived#Data=55AA0005000501010001000C DO power 0 ENDON ON TuyaReceived#Data=55AA0005000501010001010D DO power 1 ENDON

Don’t forget to turn on the rule: Rule1 1 and ‘Rule2 1’

And there it is, relatively small battery and Tasmota powered contact sensor.

Final Notes

There is a significant delay (~4s on my network with the latest stripped down binary and a static IP) between reed actuation and first MQTT message so I don’t recommmend this in critical spots where a fast response is required.

If the batteries are too weak, sensor might be stuck in a bootloop or spawn an ESP-XXXXX AP. The bootloop can reset Tasmota to “factory defaults”. You can disable bootloop protection with SetOption36 0 but that might also put the sensor in a permanent bootloop until the battery dies.