Eachen ST-DC4 Relay Board
Eachen ST-DC4

Available from:


Install method:
USB to Serial

GPIO #Component
GPIO00 Switch 1
GPIO01 User
GPIO02 User
GPIO03 User
GPIO04 Relay 3
GPIO05 Relay 2
GPIO09 User
GPIO10 User
GPIO12 Relay 1
GPIO13 LedLink
GPIO14 User
GPIO15 Relay 4
GPIO16 User
GPIO17 None

Serial Flashing

Flash the Tasmota firmware.

  • Get the latest Tasmota firmware.
  • Use Tazmotizer for flashing via serial interface.
    • Start Tasmotizer.
    • Select Serial Port.
    • Check Save original firmware.
    • Pick 1 MB from dropdown list.
    • Select BIN radio button.
    • Open latest Tasmota firmware from above.
    • Check Erase before flashing.
  • Connect USB to serial interface from computer to board with 3v jumper selected.
    1. Connect to board as follows.
USB Adapter Eachen Board
  1. Power up the Eachen Relay board with the #1 Relay button held down.
  2. Continue holding the #1 Relay button down during the entire flashing process.
  3. Hit blue Tasmotize! button in Tasmotizer. 4.1 If Tasmotizer times out with error message: ‘Failed to connect to ESP8266: Timed out waiting for packet header’, you may have to connect the 2 C66 pads on the ST-DC4 and repeat steps 2 to 4
  4. After a minute or so the Eachen board will reboot into new firmware.
  5. Unplug power from Eachen board. Wait 5 secs then replug power.

    Connect to WIFI

    • Using WIFI capable device connect to AP labeled tasmota_XXXXXX.
      (where XXXXXX is the last 6 digits of the device’s MAC addr.)
    • Once connected go to
    • Enter your WIFI information into AP1 SSID and AP1 Password and check the box beside password.
    • Hit Save.


  • Go to your Router Admin page.
    • Look for IP address of device named tasmota_XXXXXX.
      (where XXXXXX is the last 6 digits of device’s MAC addr.)
  • Enter the IP address from above into a web browser.
  • Go to Configuration, Other
    • (This step:
    • configures the device’s parameters including TuyaMCU serial COMM and 4 dummy relays used in the Rules below)
  • Copy
  • Paste into Template field.
  • Check Activate box.
  • Hit Save.
  • Device will reboot.
  • Go to Console
    • (This step sets up:
    • 9600 baud rate with so97 0
    • enables MQTT with so3 1
    • publishes TuyaReceived messages to MQTT with so66 1
    • keeps momentary timing slider from turning off dummy relay9(BUS) with so77 1
    • keeps momentary timing slider from turning on dummy relay9(BUS) with so20 1
    • assigns the Tuya MCU serial relay devices to Tasmota devices
      • relay1 with tuyamcu 11,1
      • relay2 with tuyamcu 12,2
      • relay3 with tuyamcu 13,3
      • relay4 with tuyamcu 14,4
      • all on function with tuyamcu 15,13
      • momentary timing slider with tuyamcu 21,103)
    • Copy
      backlog so97 0;so3 1;so66 1;so20 1;so77 1;tuyamcu 11,1;tuyamcu 12,2;tuyamcu 13,3;tuyamcu 14,4;tuyamcu 15,13;tuyamcu 21,103
    • Paste into Console’s Enter command space.
    • Device will reboot.
  • Go to Console
    • (This step sets up:
    • an interlock on dummy relays 6(SLM),7(MAM),8(ILKM) so only 1 relay mode may be selected with interlock 6,7,8 and interlock 1
    • 0 to 60 secs timing on momentary timing slider with dimmerrange 0,600 and dimmerstep 5)

    • Copy
      backlog interlock 6,7,8;interlock 1;dimmerrange 0,600;dimmerstep 5
    • Paste into Console’s Enter command space.
    • Device will reboot.
  • Go to Console
    • (This step:
    • names all the WebUI buttons using the first Copy/Paste
      • ALL = ALL ON button
      • SLM = Self Lock Mode (any number of relays remain ON until turned OFF)
      • MAM = Momentary Mode (uses Dimmer Slider to set ON time length from 0 to 60 secs)
      • ILKM = Interlock Mode (Only 1 relay can remain ON at a time)
      • BUS = Boot Up State (Do all relays remain OFF or turn ON when power is applied to board)
    • creates Rules to be used for
      • Boot Up State with Rule1 and
      • Relay Mode with Rule2
        using the second Copy/Paste)
  • Copy
    backlog webbutton5 ALL;webbutton6 SLM;webbutton7 MAM;webbutton8 ILKM;webbutton9 BUS
  • Paste into Console’s Enter command space.
  • Copy
    backlog rule1 on power9#state=1 do tuyasend1 101,1 endon on power9#state=0 do tuyasend1 101,0 endon;rule1 1;rule2 on power6#state=1 do tuyasend4 102,0 endon on power7#state=1 do tuyasend4 102,1 endon on power8#state=1 do tuyasend4 102,2 endon  on tuyareceived#data=55AA03070005660400010079 do power6 1 endon  on tuyareceived#data=55AA0307000566040001017A do power7 1 endon  on tuyareceived#data=55AA0307000566040001027B do power8 1 endon;rule2 1
  • Paste into Console’s Enter command space.
  • Device will reboot.
  • optional - Go to Console
    • (This step:
      • names all the devices)
    • Copy
      backlog devicename tasmota_relay01;friendlyname1 tasmota_relay01-1;friendlyname2 tasmota_relay01-2;friendlyname3 tasmota_relay01-3;friendlyname4 tasmota_relay01-4;friendlyname5 tasmota_relay01-all;friendlyname6 tasmota_relay01-slm;friendlyname7 tasmota_relay01-mam;friendlyname8 tasmota_relay01-ilkm
    • Paste into Console’s Enter command space.