New device: Tuya Smart Plug 20A with BL0942 Power Monitoring IC (#1371)

* Initial commit

* Update documentation

* Add pinout

* Add yaml example

* Update documentation

* Update documentation

* Update documentation

* Add basic configuration

* Update documentation, resolve errors

* Remove trailing space

* Fix another markdownlint issue

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Co-authored-by: Ryan Hoffman <tekmaven@users.noreply.github.com>

Author: STB3

src/docs/devices/Tuya-Smart-Plug-20A-EU_BL0942/Tuya_PCB.png

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+---
+title: Tuya Smart Plug 20A with BL0942 Power Monitoring IC
+date-published: 2025-12-07
+type: plug
+standard: eu
+board: bk72xx
+made-for-esphome: False
+difficulty: 3
+---
+
+![Tuya Smart Plug 20A](Tuya_plug_EU.png)
+![Tuya Smart Plug Aliexpress](Tuya_plug_aliexpress.png)
+
+The smart plug is using the Tuya T34 module design incorporating a BK7231N chip
+[T34 Datasheet](https://developer.tuya.com/en/docs/iot/t34-module-datasheet?id=Ka0l4h5zvg6j8)
+
+The power monitoring chip is the BL0942, which is not so often seen in Tuya products.
+It is connected using the UART feature to UART1.
+
+[BL0942 Datasheet](https://www.belling.com.cn/media/file_object/bel_product/BL0942/datasheet/BL0942_V1.06_en.pdf)
+
+[BL0942 Application](https://support.tuya.com/en/help/_detail/Kd2fly62orx3p)
+
+[BL0942 ESPHome](https://esphome.io/components/sensor/bl0942/)
+
+The BL0942 is a sophisticated, calibration-free integrated circuit (IC) for energy measurement
+from Shanghai Belling Corp.
+It is used in single-phase electricity meters, smart plugs and smart home devices to enable accurate
+measurements of voltage, current and power via a UART/SPI interface, offering a cost-effective solution
+for energy monitoring.
+
+![Tuya Smart Plug PCB view](Tuya_PCB.png)
+
+## GPIO Pinout
+
+| Pin | Function          |
+| --- | ----------------- |
+| P25 | BL0942(10) TX     |
+| P26 | BL0942(9)  RX     |
+| P14 | Relay & red LED   |
+| P26 | Button (Inverted) |
+| P24 | Blue LED          |
+
+## Programming
+
+Based on available documentation (links above) the T34 chip can be programmed using ESPHome tools
+
+- pin 25 as UART_RXD
+- pin 26 as UART_TXD
+
+It is easier to use the corresponding BL0942 pins to connect the programmers RX & TX pins.
+Programmer TX must be connected to pin 10 and RX must beconnected to pin 9.
+Connect a 5V DC source to the voltage regulator. Start programming and then cycle power of the 5V source to enter the bootloader.
+
+It is important to **limit the download speed to 19200 baud** (--upload_speed 19200) otherwise the programming terminates.
+
+## ESPHome Hardware definitions
+
+```yaml
+esphome:
+  comment: "Tuya Smart Socket EU 20A with Power Monitor"
+  name: tuya-smartplug
+
+bk72xx:
+  board: generic-bk7231n-qfn32-tuya # actually a T34 Tuya module
+  
+# Relay output
+output:
+  - platform: gpio
+    pin: P14
+    id: relay_1
+  - platform: gpio
+    pin:
+      number: P24
+      inverted: false
+    id: led_output
+
+light:
+  - platform: binary
+    name: "Status LED"  # blue LED
+    id: status_light
+    output: led_output
+
+# Local button on PCB
+binary_sensor:
+  - platform: gpio
+    id: button_1        # illuminated button
+    pin:
+      number: P26
+      mode: INPUT_PULLUP
+      inverted: true  
+
+uart:
+  id: bl0942_uart  # UART1 is used to read the data from the BL0942
+  tx_pin: TX1
+  rx_pin: RX1
+  baud_rate: 4800    
+
+# Belling BL0942 Energy Monitor
+sensor:
+  - platform: bl0942
+    uart_id: bl0942_uart
+    line_frequency: 50Hz
+    voltage:
+      name: 'Voltage'
+    current:
+      name: 'Current'
+    power:
+      name: 'Power'
+    energy:
+      name: 'Energy'
+    frequency:
+      name: "Frequency"
+
+```
+
+## ESPHome working example config
+
+```yaml
+# Programming speed must be reduced otherwise the
+# switch will will exit the flashing routine
+# Use:
+# esphome run tuya_plug.yaml --upload_speed 19200
+
+esphome:
+  comment: "Tuya Smart Socket EU 20A with Power Monitor"
+  name: tuya-smartplug
+  name_add_mac_suffix: true
+
+bk72xx:
+  board: generic-bk7231n-qfn32-tuya # actually a T34 Tuya module
+
+logger:
+    level: NONE
+
+wifi:
+  # In case a secrets.yaml file is available in the root folder
+  # with the following content:
+  # secrets.yaml
+  # wifi_ssid: "SSID"
+  # wifi_password: "PASSWORD"
+  
+  #ssid: !secret wifi_ssid
+  #password: !secret wifi_password
+  
+  ap:
+    ssid: "TuyaPlug"
+  
+captive_portal:
+
+api: 
+
+ota:
+  platform: esphome
+  
+web_server:
+  version: 3
+  port: 80  
+  
+# Relay output
+output:
+  - platform: gpio
+    pin: P14
+    id: relay_1
+  - platform: gpio
+    pin:
+      number: P24
+      inverted: false
+    id: led_output
+
+light:
+  - platform: binary
+    name: "Status LED"  # blue LED
+    id: status_light
+    output: led_output
+
+# Local button on PCB
+binary_sensor:
+  - platform: gpio
+    id: button_1        # illuminated button
+    pin:
+      number: P26
+      mode: INPUT_PULLUP
+      inverted: true  
+    filters:
+      - delayed_on: 50ms
+    on_press:
+      - switch.toggle: relay_switch  # manual control for relay
+      
+# Switch to control the relay from the UI
+switch:
+  - platform: output
+    name: "Relay"
+    id: relay_switch
+    output: relay_1
+    
+uart:
+  id: bl0942_uart  # UART1 is used to read the data from the BL0942
+  tx_pin: TX1
+  rx_pin: RX1
+  baud_rate: 4800    
+
+# Belling BL0942 Energy Monitor
+sensor:
+  - platform: bl0942
+    uart_id: bl0942_uart
+    line_frequency: 50Hz
+    voltage:
+      name: 'Voltage'
+    current:
+      name: 'Current'
+    power:
+      name: 'Power'
+    energy:
+      name: 'Energy'
+    frequency:
+      name: "Frequency"
+      
+  - platform: wifi_signal
+    name: "TuyaPlug WiFi Signal"
+    id: wifi_signal_sensor
+    update_interval: 60s        
+```