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Exploring the Inner Workings of PJ-MGW1103 CT-Clamp Energy Meter: Tuya, BL0942, CB2S Components

TurkeyMan 26988 134
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How do I map the PJ-MGW1103 CT-clamp meter’s TuyaMCU datapoints and interpret the BL0942/CB2S connections?

This meter is best treated as a TuyaMCU device: the Wi‑Fi module talks to a separate MCU over UART, and the BL0942 is not directly driven by the Wi‑Fi chip, so OpenBK should use the TuyaMCU driver rather than the BL0942 driver [#20590482][#20591181][#20527903] For the original single-clamp captures, the working readings were dPID 20 = voltage, dPID 19 = power, and dPID 18 = current, with the Tuya app’s “maximum power” setting being sent to the MCU as a configuration value rather than just a UI-only percentage [#20527903] For later working OpenBK configs, users reported that 9600 baud was required on some units, sometimes with the CEN/reset trace disconnected to stop the MCU from resetting the Wi‑Fi module [#21429711] A full two-clamp mapping was posted: voltage on dPID 112, current on 113/114, power on 101/105, frequency on 111, power factor on 110/121, energy on 106-109, plus calibration/reporting DPs on 116-129 [#21041947][#21114187] If you want faster updates, the MCU can be polled with `tuyaMcu_sendQueryState`, and the reporting rate itself is exposed as dPID 129 [#20882643][#20882899][#21114187]
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  • #91 20882983
    tony059560
    Level 4  
    Posts: 6

    Thanks!

    Here is the content of my autoexec.bat:

    Code: text Expand Select all Copy to clipboard
    
// config for PJ-MGW1103 CT-Clamp Energy Meter by Tuya, BL0942, CB2S Components
startDriver TuyaMCU
tuyaMcu_setBaudRate 115200
tuyaMcu_defWiFiState 4
setChannelType 2 Voltage_div10
setChannelType 3 Power_div10
setChannelType 4 Current_div1000
// linkTuyaMCUOutputToChannel dpId variableType tgChannel
//ch 2(dpid 20) voltage
linkTuyaMCUOutputToChannel 20 1 2
//ch 3(dpid 19) power watts
linkTuyaMCUOutputToChannel 19 1 3
//ch 4(dpid 18) current in mA
linkTuyaMCUOutputToChannel 18 1 4
// every 15 seconds query measurements from the MCU
addRepeatingEvent 5 -1 tuyaMcu_sendQueryState

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  • #92 20883121
    p.kaczmarek2
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    What about:


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  • #93 20883161
    tony059560
    Level 4  
    Posts: 6

    I've watched this video before but the problem is that when I click on the "Home Assistant Configuration" button, the area where there should be an automatically generated configuration is empty.
    However, I have configured the parameters related to MQTT. In addition, in the main menu, it tells me that the MQTT is connected.

    I still tried to click on the "Start Home Assistant Discovery" button. This new device appeared in my list of MQTT devices in Home Assistant and after a few minutes, the information was correctly displayed.

    In summary, we can still launch Home Assistant discovery, even if the configuration is empty.

    One last question (for beginners), is whether we have the possibility of reinjecting the official firmware in order to be able to integrate it again into the Tuya application. I know I'm not going to do it but I would like to know if it's possible. And if it's possible, where can we find the official firmware and how to re-inject it?
    I think it's useful to know that.
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  • #94 20883210
    p.kaczmarek2
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    The text field is only for basic devices, but HA Discovery button works also for advanced ones, most of the time.

    Our flashing tool, BK7231tools easy flasher:
    https://github.com/openshwprojects/BK7231GUIFlashTool
    Is automatically making a 2MB flash backup on read, so you can always restore device to Tuya with that backup. This is why I always recommend to make a backup first.
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  • #95 20922252
    tony059560
    Level 4  
    Posts: 6

    Hello,
    Can we configure the state of the smart plug when it is plugged in or put it in the state it was in before it was turned off?
    Currently, when my smart plug has no power and then it has power again, its status is off.
  • #96 20922273
    p.kaczmarek2
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    It is possible but it's a bit more complicated in the case of TuyaMCU device.
    Please see this tutorial:
    How to configure TuyaMCU initial switch state? dpID and script methods for OpenBeken
    You will need to use:
    Code: text Expand Select all Copy to clipboard
    Method 2 - Manual OBK state save
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    #97 21041947
    nielspiersma
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    Hi All,

    I would like to share that I've successfully got the two clamps version working;
    It did take me a while getting all the required information together, so here a quick write up on the two-clamp version;

    1. Flash the device using tuya-cloudcutter (the device is on the device list as generic "Tuya PJ-MGW1103 "
    2. connect to your wifi
    3. paste the correct autoexec.bat (post 77 https://www.elektroda.com/rtvforum/topic3946128-60.html#20851047)

    Code: text Expand Select all Copy to clipboard
    
startDriver TuyaMCU
tuyaMcu_setBaudRate 9600
tuyaMcu_defWiFiState 4
setChannelType 2 Voltage_div10
setChannelType 3 Current_div1000
setChannelType 4 Current_div1000
setChannelType 5 Frequency_div100
setChannelType 6 Power_div10
setChannelType 7 Power_div10
setChannelType 8 PowerFactor_div100
setChannelType 9 PowerFactor_div100
// linkTuyaMCUOutputToChannel dpId variableType tgChannel
//ch 2(dpid 20) voltage
linkTuyaMCUOutputToChannel  112 1 2
//ch 3(dpid 19) power watts
linkTuyaMCUOutputToChannel 113 1 3
linkTuyaMCUOutputToChannel 114 1 4
//ch 4(dpid 20) frequency
linkTuyaMCUOutputToChannel  111 1 5
linkTuyaMCUOutputToChannel  101 1 6
linkTuyaMCUOutputToChannel  105 1 7
linkTuyaMCUOutputToChannel  110 1 8
linkTuyaMCUOutputToChannel  121 1 9


    4. reboot
    5. done!

    My device:
    Circuit board of the Tuya PJ-MGW1103 device in a dual-clamp version.
    Image of a circuit board with electronic components and connectors.
    Circuit board with electronic components, including terminals and a blue module.
    Image of an electronic module with a green terminal block and various components.
    Electronic board with components for modifying a Tuya device.

    Lessons learned:
    baud rate needs to be 9600
    no hardware fiddling is required

    Proof;:
    Screenshot showing information about the OpenBK7231N device.     .
  • #98 21042266
    p.kaczmarek2
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    Good job. I think you can also improve your config by setting channel labels.
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  • #99 21047391
    bf1648
    Level 4  
    Posts: 3
    Hello everyone
    I have a device with Aliexpress "Double Digital Meter". There are two bl0942 chips on the bk7231n board - the first connects to uart1, the second is connected to uart2. There is no Tuya mcu on the board. A channel that works fine on uart1 with the bl0942 driver enabled. How can I make the second channel on uart2 work? Maybe someone can help?
  • #100 21048398
    p.kaczmarek2
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    Hello! Are you sure that your question is related to the device from the first post? Maybe I should move it to the separate topic?

    Supporing two BL0942's via UART requires a firmware modification, but we can do it together. Do you know C basics?
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  • #101 21048480
    bf1648
    Level 4  
    Posts: 3

    Thanks for the answer!
    I'm sorry, but a similar device was discussed in this topic, but with a different board.
    I know very little about C, but I hope that with your help I can figure it out.

    And I'm sorry for the spelling - English is not my native language, I use google translator.
  • #102 21049535
    snkbrzmir4
    Level 4  
    Posts: 7
    Hello, checking the logs I discovered that dpid 115 shows the power with the same flow, but the sign is inverted, in dpid 101 it always shows positive, in 115 it shows negative if it is positive and positive if the flow inverts, I did the test here with my ongrid inverter. I haven't discovered how to invert the sign to show it in homeassistant, I believe that simply multiplying by -1 would solve it without any major problems. I appreciate anyone who can help me, I'm new to openbk, but I already have others with it installed, but they are normal smart switches without any major complications.

    Thanks in advance for any help.

    It's also taking a long time between updates, it's like doing it every 1 second?
  • #103 21049968
    p.kaczmarek2
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    snkbrzmir4 wrote:
    I haven't discovered how to invert the sign to show it in homeassistant, I believe that simply multiplying by -1 would solve it without any major problems.

    Sure, that's a good idea, I added a way to do that.
    Please update the firmware.
    You can now specify a multiplier, -1, for example.
    A section of documentation about the linkTuyaMCUOutputToChannel function with instructions and explanations.
    remember to also specify dpCache value (0 in your case)

    snkbrzmir4 wrote:

    It's also taking a long time between updates, it's like doing it every 1 second?

    You could try to query updates faster but I am not sure if that MCU supports it.
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  • #104 21050425
    snkbrzmir4
    Level 4  
    Posts: 7

    Thank you for your feedback, after I thought a little I realized that the clamp can be placed in 2 positions and if I was measuring wrong I had placed it inverted, my fault, I apologize for this error. Regarding sending in a shorter time, it does not seem to be possible, the measurement only comes every 10 seconds, even using the tuyaMcu_sendQueryState command it only responds every 10 seconds. But I saw that the shellyEM that I'm wanting to replace and has a problem and measures incorrectly, sends more than 10s, so it's better than the shelly. Thank you for the help, I'll put names on all the channels and put the second clamp and generate a template to contribute to this at least :)
  • #105 21050470
    p.kaczmarek2
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    You're welcome, please post any templates, information, teardowns you can get. We're making a devices database and we want to get to 600 entries soon:
    https://openbekeniot.github.io/webapp/devicesList.html
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  • #106 21050660
    bf1648
    Level 4  
    Posts: 3

    Here is a photo of my "Double Digital Meter" that I asked about above.
    Dual-channel single-phase clamp with Wi-Fi for current measurement. Image of a printed circuit board with electronic components. Photo of an electronic module with several capacitors and components soldered onto a circuit board. Image of a dual digital meter with visible capacitors and a Wi-Fi module on a green PCB. Black plastic sensor with a red wire on a wooden surface.

    Added after 4 [minutes]:

    p.kaczmarek2, can you help me with the firmware modification?

    Added after 7 [minutes]:

    One bl0942 is soldered to UART_TX1, UART_RX1 (pin 15, 16). The second bl0942 is soldered to UART_TX 2, UART_RX2 (pin 6, 7).

    Added after 4 [minutes]:

    wi-fi led on P9
  • #108 21108761
    erdeidominik1999
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    Hello!
    Is the total used kWh calculated by the Tuya firmware? Is there any way to use that value?
  • #109 21108796
    p.kaczmarek2
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    i had the same meter and i described my experience in this topic:
    https://www.elektroda.com/rtvforum/topic4053493.html
    I want not able to find a "total used kwh" dpID in that case, but you can also try this method:
    https://www.elektroda.com/rtvforum/topic4021129.html
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  • #110 21110187
    erdeidominik1999
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    >>21108796 I extracted some dp-s from serial and I found some info on a forum, now I have info from the whole calibration dp-s, I will write a summary tomorrow, how can I use the calibration easily in openbk? It only sets dp-s on the tuyamcu.
  • #111 21110284
    p.kaczmarek2
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    Use TextField channel type.
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  • #112 21110915
    erdeidominik1999
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    >>21110284Thank you, I reconfigured everything and now the dp value is not set to the channels, the log:
    Info:TuyaMCU:Received: 55 AA 03 07 00 08 65 02 00 04 00 00 01 A0 1D
    Info:TuyaMCU:ProcessIncoming[v=3]: cmd 7 (State) len 15
    Info:TuyaMCU:ParseState: id 101 type 2-val len 4
    Info:TuyaMCU:ParseState: int32 416
    Info:GEN:No change in channel 6 (still set to 0) - ignoring

    and the autoexec for that channel:
    setChannelType 6 Power_div10
    SetChannelLabel 6 "Teljesítmény (A)"
    linkTuyaMCUOutputToChannel 101 1 6 //power A

    But why it says that there is no change?
  • #113 21112085
    p.kaczmarek2
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    just to be sure, can you reboot your device?
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  • #114 21113131
    erdeidominik1999
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    >>21112085
    Yes, but I found the problem, the comments at the end of the lines, if I put them to a new line it works. I successfully made a lot of dps working, but the calibration data is not working, I made textfield channels, mapped them, the dp gets read from the tuyamcu, but I cannot set the value, if I set a new value at the web page, it not changes, and I cannot see in the logs, that openbk send it to the tuyamcu.
  • #115 21113324
    p.kaczmarek2
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    I will try to check that, but in a meantime, have you tried to use the command to send dpID value directly?
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    #116 21114187
    erdeidominik1999
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    p.kaczmarek2 wrote:
    I will try to check that, but in a meantime, have you tried to use the command to send dpID value directly?


    Okay, I think I made everything working, the total values, the calibration, and the update frequency also works. This is my autoexec.bat:
    Code: text Expand Select all Copy to clipboard
    startDriver TuyaMCU
tuyaMcu_setBaudRate 9600
tuyaMcu_defWiFiState 4

//voltage
setChannelType 2 Voltage_div10
SetChannelLabel 2 "Voltage"
linkTuyaMCUOutputToChannel  112 1 2

//current A
setChannelType 3 Current_div1000
SetChannelLabel 3 "Current(A)"
linkTuyaMCUOutputToChannel 113 1 3

//current B
setChannelType 4 Current_div1000
SetChannelLabel 4 "Current(B)"
linkTuyaMCUOutputToChannel 114 1 4

//frequency
setChannelType 5 Frequency_div100
SetChannelLabel 5 "Frequency"
linkTuyaMCUOutputToChannel  111 1 5 

//power A
setChannelType 6 Power_div10
SetChannelLabel 6 "Power(A)"
linkTuyaMCUOutputToChannel  101 1 6 

//power B
setChannelType 7 Power_div10
SetChannelLabel 7 "Power(B)"
linkTuyaMCUOutputToChannel  105 1 7 

//power factor A
setChannelType 8 PowerFactor_div100
SetChannelLabel 8 "Power factor(A)"
linkTuyaMCUOutputToChannel  110 1 8

//power factor B
setChannelType 9 PowerFactor_div100
SetChannelLabel 9 "Power factor(B)"
linkTuyaMCUOutputToChannel  121 1 9 

//forward energy A
setChannelType 10 EnergyTotal_kWh_div1000
SetChannelLabel 10 "Total energy(A)"
linkTuyaMCUOutputToChannel  106 1 10

//forward energy B
setChannelType 11 EnergyTotal_kWh_div1000
SetChannelLabel 11 "Total energy(B)"
linkTuyaMCUOutputToChannel  108 1 11 


//reporting rate
setChannelType 12 TextField
SetChannelPrivate 12 true
SetChannelLabel 12 "Reporting rate"
linkTuyaMCUOutputToChannel  129 val 12

//voltage calibration
setChannelType 13 TextField
SetChannelPrivate 13 true
SetChannelLabel 13 "Voltage calibration"
linkTuyaMCUOutputToChannel  116 val 13

//current A calibration
setChannelType 14 TextField
SetChannelPrivate 14 true
SetChannelLabel 14 "Current(A) calibration"
linkTuyaMCUOutputToChannel  117 val 14

//power A calibration
setChannelType 15 TextField
SetChannelPrivate 15 true
SetChannelLabel 15 "Power(A) calibration"
linkTuyaMCUOutputToChannel  118 val 15

//energy A calibration
setChannelType 16 TextField
SetChannelPrivate 16 true
SetChannelLabel 16 "Total energy(A) calibration"
linkTuyaMCUOutputToChannel  119 val 16

//frequency calibration
setChannelType 17 TextField
SetChannelPrivate 17 true
SetChannelLabel 17 "Frequency calibration"
linkTuyaMCUOutputToChannel  122 val 17

//current B calibration
setChannelType 18 TextField
SetChannelPrivate 18 true
SetChannelLabel 18 "Current(B) calibration"
linkTuyaMCUOutputToChannel  123 val 18

//power B calibration
setChannelType 19 TextField
SetChannelPrivate 19 true
SetChannelLabel 19 "Power(B) calibration"
linkTuyaMCUOutputToChannel  124 val 19

//energy B calibration
setChannelType 20 TextField
SetChannelPrivate 20 true
SetChannelLabel 20 "Total energy(A) calibration"
linkTuyaMCUOutputToChannel  125 val 20

addRepeatingEvent 10 1 SetChannel 12 3


    I found the attached images, and the dps were correct.

    List of selected options on a program screen Configuration list with checked options for calibration of various parameters, such as voltage and current.
  • #117 21114190
    p.kaczmarek2
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    Thank you for sharing, if I may ask, can you also share autoexec.bat in english so I can add it to our examples?
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  • #118 21114201
    erdeidominik1999
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    >>21114190 I edited the post.
  • #119 21115686
    erdeidominik1999
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    >>21114190
    I found a problem, the EnergyTotal needs div 100 not div 1000, but the openbk has only EnergyTotal_kWh_div1000.
  • #120 21115933
    p.kaczmarek2
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    You can now add a custom mult while linking dpID to channel:
    Excerpt from technical documentation with syntax examples and links.
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Topic summary

✨ The discussion centers on the teardown, firmware flashing, and configuration of the PJ-MGW1103 CT-Clamp Energy Meter, which integrates Tuya MCU, BL0942 energy measurement IC, and CB2S WiFi module components. Users shared detailed hardware photos and identified the device’s internal architecture, including the separate MCU and WiFi modules. The device communicates via TuyaMCU protocol at 115200 or 9600 baud, with data points (dpIDs) representing voltage, current, power, frequency, and power factor. Key challenges include decoding dpIDs, configuring OpenBK firmware for accurate data reading, and handling device resets caused by the CEN line. Calibration data resides on the MCU, not lost when flashing OpenBK, but calibration dpIDs and their writable nature remain partially unclear. Users developed autoexec.bat scripts to map dpIDs to OpenBK channels, enabling voltage, current, power, frequency, and power factor monitoring. Polling frequency is limited (~10 seconds), and energy accumulation is estimated rather than precise due to MCU reporting behavior. Firmware flashing methods include desoldering pads for UART access and using Tuya cloud cutter tools. Some users reported device instability linked to CEN line and baud rate settings, resolved by disconnecting CEN and setting baud to 9600. The community also discussed integration with Home Assistant via MQTT and the possibility of restoring original Tuya firmware from backups. A two-clamp version was successfully configured with extended dpID mappings. Additional topics include support for dual BL0942 chips on separate UARTs requiring firmware modification, and the use of OpenBK’s scripting to automate state queries and improve update frequency. Overall, the thread provides a comprehensive technical resource for reverse engineering, firmware customization, and integration of the PJ-MGW1103 energy meter within open-source ecosystems.
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FAQ

TL;DR: PJ-MGW1103/1103A CT-clamp meters stream 2403 raw volts = 240.3 V at 9600 baud and can push updates every 1-10 s once dpIDs are mapped correctly [Elektroda, tony059560, post #20882269] “Everything seems to be ok” — p.kaczmarek2 [Elektroda, 20849273]

Why it matters: Correct dpID mapping unlocks bidirectional kWh, sign-aware power and MQTT/HA export without extra hardware.

Quick Facts

• Measurement range: 0.2 A – 80 A per clamp [Elektroda, randomalias324, post #21429711] • Default UART: 9600 bps, 8 N 1 [Elektroda, thalesmaia, post #20848010] • MCU report frame: 55 AA 03 …, State cmd 0x07 every ≈10 s (adjustable) [Elektroda, erdeidominik1999, post #21114187] • Key dpIDs: 18 = I, 19 = P, 20 = V; sign bits 102/104 [Elektroda, snkbrzmir4, post #21117274] • Calibration dpIDs: 116-125 (V, I, P, Wh, F) [Elektroda, erdeidominik1999, post #21114187]

How do I get live voltage, current and power?

Flash OpenBeken, add tuyaMcu_setBaudRate 9600, then map dpIDs 20→Voltage_div10, 18→Current_div1000, 19→Power_div10 in autoexec.bat. A sample ready-to-paste set is shown in post #21114187 [Elektroda, erdeidominik1999].

My current shows zero on low loads—faulty?

The clamp needs at least 0.2 A; values below give 0 because of internal threshold in BL0942 [Elektroda, tony059560, post #20882488] Use a ≥60 W resistive load for testing.

Can I invert power when the energy flow reverses?

Yes. Use the sign bit dpIDs (102 for clamp A, 104 for clamp B) and an event handler:
  1. alias pos setChannel X $CHp
  2. alias neg setChannel X $CHp*-1
  3. addEventHandler OnChannelChange p/ sign myset Full script in example file commit 1.17.619 [Elektroda, p.kaczmarek2, post #21125287]

Where are total kWh values stored?

The STM32 (MCU) accumulates Wh and exposes them as dpIDs 1/2 (device total) and 106-109 (per clamp). They survive Wi-Fi reflash but are lost if the MCU is power-cycled for several minutes [Elektroda, randomalias324, post #21429711]

How do I calibrate voltage or current?

Set dpIDs 116 (V), 117 (I₁), 118 (P₁), 122 (F), 123 (I₂) etc. via TextField channels, then write the desired integer. No BL0942 driver calibration is required because values are stored in MCU flash [Elektroda, erdeidominik1999, post #21114187]

How to restore original Tuya firmware?

BK7231 GUI flasher auto-saves a 2 MB backup on first read; flash it back with the same tool to regain Tuya SmartLife pairing [Elektroda, p.kaczmarek2, post #20883210]

Can I use ESPHome instead of OpenBeken?

Yes. Map the same dpIDs over UART1 at 9600 bps. A full ESPHome YAML template is in post #21443304 [Elektroda, dragonmen].

Does clamp orientation matter?

Yes. Reverse wiring flips the sign bit, leading to negative totals. Align the arrow with conventional current flow or adjust sign logic in script [Elektroda, randomalias324, post #21429711]

Quick 3-step flashing guide?

  1. Use Tuya-cloudcutter profile “PJ-MGW1103”.
  2. On first boot, connect to AP and enter Wi-Fi.
  3. Upload autoexec, reboot, confirm dpID frames in log [Elektroda, thalesmaia, post #20851047]
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