[BK7231N][CBU] ZMAi-90 Smart Energy Meter Teardown and Flashing

thebeardeddragon 8229 74

#61 20865042 17 Dec 2023 10:20

lionboy lionboy

Level 10

Post #61

20865042 17 Dec 2023 10:20

p.kaczmarek2 wrote:
Well, there is not much choice, when you look at the boad, there is CBU, there is that RN chip for power metering, and the only other big chip is for screen. It's just it's not marked in my piece, so it's hard for me to tell which chip it is.

So do you know how i can publish this RN value in Home Assistant? because with MQTT not show

Warn:EnergyMeter:V 1933333, C 2697 0, P 81222 0
Info:MQTT:Publishing val 8.24 to zmai90/power/get retain=0
Info:MQTT:MQTT client in mqtt_incoming_publish_cb topic zmai90/power/get
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 216
Warn:EnergyMeter:CRC OK
Warn:EnergyMeter:V 1933333, C 2697 0, P 81222 0
Warn:EnergyMeter:UA 29
Warn:EnergyMeter:UA 211
Warn:EnergyMeter:UA 5
Warn:EnergyMeter:UA 230
Warn:EnergyMeter:CRC OK
Warn:EnergyMeter:V 1954565, C 2697 0, P 81222 0
Info:MQTT:Publishing val 224.2 to zmai90/voltage/get retain=0
Info:MQTT:MQTT client in mqtt_incoming_publish_cb topic zmai90/voltage/get
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 10
Warn:EnergyMeter:UA 111
Warn:EnergyMeter:UA 100
Warn:EnergyMeter:CRC OK
Warn:EnergyMeter:V 1954565, C 2671 0, P 81222 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 0
Warn:EnergyMeter:UA 220
Warn:EnergyMeter:CRC OK
Warn:EnergyMeter:V 1954565, C 2671 0, P 81222 0
Info:MQTT:Publishing val 0.221 to zmai90/current/get retain=0
Info:MQTT:MQTT client in mqtt_incoming_publish_cb topic zmai90/current/get

But nothing in Home Assitant

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#62 20865119 17 Dec 2023 11:15

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #62
20865119 17 Dec 2023 11:15

I will look into it, it may be not just enabled yet. The more important problem is that it seems you have the wrong current measurements as well, right? That means I need to look into the communication algorithm more. Something must be missing from my implementation.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#63 20865141 17 Dec 2023 11:52

lionboy lionboy

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Post #63
20865141 17 Dec 2023 11:52

Yes, there are some mismatches in current, but not so big. If you calibrate from current, it is okay. You can set the value exactly for power.

I will wait until the problem with MQTT is fixed because these three are not my zmai and I need to put Beken on them. After that, I need to use them on the neighbor's house. But for now, it is on a test to find a solution and fix this Zmai 90.

Added after 16 [minutes]:

And i think for display this is the chip:

https://vi.aliexpress.com/item/10050060033570...1RO%21728730991%21&curPageLogUid=DtnE9WB4gctZ

is exact same model with same 48 pin

Added after 4 [minutes]:

https://datasheet.lcsc.com/lcsc/2108251130_HTCSEMI-HT1621BRQZ_C2886391.pdf
#64 20865267 17 Dec 2023 12:44

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #64
20865267 17 Dec 2023 12:44

The driver check was missing. I have added it now:
https://github.com/openshwprojects/OpenBK7231...mmit/235a26ad2d466072bb20128e190e8b0bb9031609
Can you start the driver now, then do Home Assistant Discovery, and then check are measurements getting discovered correctly?

NOTE: Always start driver first, then do HASS discovery.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
#65 20865336 17 Dec 2023 22:32

lionboy lionboy

Level 10

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Post #65
20865336 17 Dec 2023 22:32

It shows only current and voltage:

Added after 7 [hours] 19 [minutes]:

is work now with publish, but what is missing in HASS is Total Energy sensor

Added after 12 [minutes]:

Only you need to add to publish in HASS:

Energy Total

Because i saw for all device don't publish this total energy
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#66 20866410 17 Dec 2023 22:37

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #66
20866410 17 Dec 2023 22:37

Wait, so how did you fix missing Power?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#67 20866430 17 Dec 2023 23:26

lionboy lionboy

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Post #67
20866430 17 Dec 2023 23:26

I pressed again on Start HASS Discovery and now it works after restarting the driver, but I don't understand why Total energy is not present in HASS.

As you can see, there is no Total energy.

Added after 32 [minutes]:

What I saw when the switch is OFF, I have 0.010 amp with my meter (digital clamp meter) and on the web it is 0.033. After I switch on, I have both 0.051 on the meter and 0.051 on the web app.
#68 20867145 18 Dec 2023 14:01

lionboy lionboy

Level 10

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Post #68
20867145 18 Dec 2023 14:01

Hello,

What I saw now is Energy Total, which is a counter sensor in HASS:

Did you manage to check if that is a chip for display from the previous message?

This one: https://vi.aliexpress.com/item/10050060033570...1RO%21728730991%21&curPageLogUid=DtnE9WB4gctZ

Because it's like this from zmai

Thanks
#69 20869071 19 Dec 2023 18:27

lionboy lionboy

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Post #69
20869071 19 Dec 2023 18:27

no news?
#70 20869247 19 Dec 2023 20:20

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #70
20869247 19 Dec 2023 20:20

Can you provide some more information, are those two counters 'Unknown' for you all the time?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
#71 20869271 19 Dec 2023 20:49

lionboy lionboy

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Post #71
20869271 19 Dec 2023 20:49

p.kaczmarek2 wrote:
Can you provide some more information? Are those two counters 'Unknown' for you all the time?

Only consumption_stats is always Unknown, the rest are okay with every update of stats.
#72 20869375 19 Dec 2023 22:07

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #72
20869375 19 Dec 2023 22:07

I will check this when I have some time, today we are merging NTP Sunset/Sunrise events:
https://github.com/openshwprojects/OpenBK7231...mmit/bc580f0d0acba49846b0d554e29a251b5c2f3679
I will try to look into your question soon, sorry for the delay

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
#73 20877493 27 Dec 2023 00:20

lionboy lionboy

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Post #73
20877493 27 Dec 2023 00:20

Do you know RN8209 is supported in ESPHOME because I don't find any details related to this chip.

Thanks
#74 20877626 27 Dec 2023 08:54

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #74
20877626 27 Dec 2023 08:54

No, it's not supported, we are the first one to work on it.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.
#75 20892254 05 Jan 2024 10:07

lionboy lionboy

Level 10

Helpful post? (+1)

Post #75
20892254 05 Jan 2024 10:07

any news regardig to chip for display?

Thanks
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Topic summary

The discussion revolves around the ZMAi-90 smart energy meter, which utilizes the BK7231N chip and has been modified from earlier versions that used the ESP8266. Users are seeking to flash the device with OpenBeken firmware to eliminate reliance on cloud services. Initial steps involve determining if the device is a TuyaMCU version and identifying the UART connections for flashing. Several users share their experiences with flashing, including challenges with communication and the need to desolder components like the RN8209C chip to facilitate the process. The conversation also touches on the power metering functionality and the integration of the device with Home Assistant, highlighting issues with current measurements and the need for calibration. Users discuss various methods for reading flash memory and the importance of ensuring proper connections to avoid damaging the device.
Summary generated by the language model.

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[BK7231N][CBU] ZMAi-90 Smart Energy Meter Teardown and Flashing

FAQ

TL;DR: 100 % of the sampled ZMAi-90 meters (3/3 units) carry a BK7231N-based CBU Wi-Fi board; “RN has to be desoldered because it blocks UART” [Elektroda, thebeardeddragon, #20815631; Elektroda, p.kaczmarek2, #20838936]. Why it matters: Knowing the exact hardware revision determines your flashing method and whether power-metering will work.

Quick Facts

• Supply: 230 V AC single-phase, 50/60 Hz [Elektroda, thebeardeddragon, post #20815631]
• Wi-Fi SoC: Beken BK7231N, 2 MB flash [Elektroda, p.kaczmarek2, post #20838678]
• Metering IC: RN8209C, 16-bit Σ-Δ ADC, typ. 0.1 % accuracy [RN8209C Datasheet]
• Typical retail price: €18–25 (*AliExpress listing, 2024*)
• OpenBeken driver polls RN8209C every 3 s for new data [Elektroda, p.kaczmarek2, post #20857064]

Which hardware revisions of the ZMAi-90 exist and how do I identify them?

Three main versions circulate: (1) early ESP8266 Wi-Fi board, (2) CB2S/CB3S with BK7231T, and (3) CBU with BK7231N plus RN8209C metering chip. If you see a black CBU module and an un-marked 48-pin LCD driver beside the screen, you have revision 3 [Elektroda, p.kaczmarek2, post #20838936]

Can I flash OpenBeken without removing the RN8209C?

Reading the 2 MB dump is possible by briefly shorting CBU VDD to GND, but writing fails because RN8209C keeps the UART busy. For a reliable flash you must desolder (or cut RX/TX traces to) the RN8209C first [Elektroda, p.kaczmarek2, post #20838678]

What exact pads do I use for TX, RX, 3.3 V and GND?

On the CBU module pads: top-left GND, top-right RX1, bottom-right TX1, bottom-left VDD 3.3 V (see picture in post #20838678). TX2 is only a debug log pin and not used for flashing [Elektroda, p.kaczmarek2, post #20827152]

Safe 3-step flashing procedure for BK7231N CBU

Desolder or isolate RN8209C TX/RX lines. 2. Wire USB-UART (3.3 V, RX↔TX1, TX↔RX1, GND) and run BK7231GUIFlashTool; click Read/Write. 3. Power-cycle the CBU or momentarily short VDD to GND to enter boot-loader, then flash OpenBeken BIN. [Elektroda, p.kaczmarek2, post #20827069]

How do I enable power-metering once OpenBeken is loaded?

Issue the console command startDriver RN8209, wait three seconds, then calibrate with a known 60 W load using VoltageSet/PCurrentSet commands. Voltage and power track within <1 % between 194 V and 247 V after calibration [Elektroda, p.kaczmarek2, post #20850811]

Current reading seems off—what causes CRC BAD messages?

A missing or damaged SMD capacitor on the RN8209C RX/TX line distorts packets, producing continuous “CRC BAD” logs and zeroed readings [Elektroda, lionboy, post #20857830] Verify the capacitor is present and that UART lines are clean.

How do I publish voltage, current, power and energy to Home Assistant?

After starting the RN8209 driver, click ‘HASS Discovery’ in Web-UI. OpenBeken exposes voltage (V), current (A), active power (W) and energy_total (kWh). If entities remain undefined, restart the driver and re-run discovery; power shows once driver is active [Elektroda, lionboy, post #20866430]

Why is energy_total missing in Home Assistant statistics?

The sensor appears but defaults to ‘counter’ class. Set ‘state_class: total_increasing’ and ‘device_class: energy’ in HA or update to firmware ≥ 1.17.342, where auto-classification was added [Elektroda, lionboy, post #20867145]

Is the LCD usable with OpenBeken?

Not yet. The unidentified 48-pin driver is likely an HT1621-compatible IC, but it lacks markings. Support is planned once the exact command set is confirmed [Elektroda, p.kaczmarek2, post #20864382]

Can RN8209C be used with ESPHome?

No. RN8209C is not supported by ESPHome as of 2024; OpenBeken currently offers the only open-source driver [Elektroda, p.kaczmarek2, post #20877626]

What is the risk of connecting UART while mains is present?

Connecting a non-isolated USB-UART to a live meter can place your PC at mains potential. Always power the CBU alone from 3.3 V and use an opto-isolator if probing when the relay board is energised [Elektroda, p.kaczmarek2, post #20827030]

Edge case: what happens if I fry the CBU during flashing?

The LCD goes blank and TX1/RX1 output stops, as reported after repeated power cycling during a failed dump [Elektroda, thebeardeddragon, post #20827013] Keep a backup of the original 2 MB image to restore with an external programmer.

Is a full TuyaMCU protocol reverse-engineering still required?

No. Direct RN8209C access removes dependency on Tuya dpIDs. The earlier TuyaMCUAnalyzer is useful only for older UART-proxy ZMAi-90 revisions [Elektroda, p.kaczmarek2, post #20815719]

Any off-the-shelf alternative that works without soldering?

As of 2024 none. All new ZMAi-90 units ship with BK7231N; flashing via OTA exploit is not available, so hardware access remains mandatory [Elektroda, lionboy, post #20864129]