FAQ
TL;DR: Tuya-based boiler switch on BK7231N with a 20 A latching relay; "touch-sensing chip outputs four distinct analog levels." It maps LEDs, coils, ADC, and BL0942 pins for DIY control. [Elektroda, seeindarkness, post #21771967]
Why it matters: This FAQ helps tinkerers flash, map, and script OpenBeken on the EZS‑WBA1H20C board to get reliable timed switching and metering.
Quick Facts
- Board: EZS‑WBA1H20C‑AA V1.4 (2021‑12‑31) with BK7231N Wi‑Fi MCU. [Elektroda, seeindarkness, post #20967494]
- Relay: magnetically held (latching); ON coil at P24, OFF coil at P26. [Elektroda, seeindarkness, post #20967494]
- Touch input: Pin 28 reads four button levels (~25, ~1810, ~2685, ~3623; ~4000 idle). [Elektroda, seeindarkness, post #21771967]
- Energy metering IC: BL0942; J1 exposes GND, 3.3 V, TX/RX lines. [Elektroda, seeindarkness, post #21771967]
- OpenBeken template pins for LEDs, coils, ADC published by users. [Elektroda, seeindarkness, post #21784551]
What exactly is this water boiler/heater switch?
It’s a Tuya smart boiler switch using BK7231N on board EZS‑WBA1H20C‑AA V1.4. It includes a 20 A latching relay, four touch buttons, and indicator LEDs. Users opened the unit, photographed PCBs, and confirmed markings and relay type. This FAQ summarizes their working pin map and behavior. [Elektroda, seeindarkness, post #20967494]
How are the four touch buttons read on BK7231N?
A dedicated touch-sensing chip feeds BK7231N Pin 28 as four analog levels. Reported readings: about 25 (Pad 1), 1810 (Pad 2), 2685 (Pad 3), 3623 (Pad 4), with ~4000 when idle. Quote: "Pin 28 interprets as 4 distinct analog levels." Use an ADC channel in OpenBeken to react to thresholds. [Elektroda, seeindarkness, post #21771967]
What’s the working pin template for LEDs, coils, and ADC?
Community template maps LEDs to pins 6, 14–17, 20, 22–23; Wi‑Fi LED at pin 9; latching relay coils: Rel 39 at pin 24 (ON) and Rel 37 at pin 26 (OFF); touch ADC at pin 28 (CH20). Apply this in OpenBeken’s Template. [Elektroda, seeindarkness, post #21784551]
How do I drive the latching relay safely with OpenBeken?
Use separate pulses for ON and OFF coils. Map Channel1 as logical state; pulse Channel39 for ON and Channel37 for OFF for 0.2–1 s. The provided autoexec.bat shows startup OFF pulse and change handlers that convert state changes into coil pulses. "Short pulses protect the coil." [Elektroda, seeindarkness, post #21775536]
Is there a simple 10‑minute auto‑off timer example?
Yes. A compact script toggles Channel1 from the ADC press and adds a 600‑second auto‑off event. It also generates 0.2‑second coil pulses on ON and OFF. Copy the example autoexec.bat from the thread and adjust pulse time if needed. [Elektroda, seeindarkness, post #21775536]
How do I map the BL0942 metering IC pins on this board?
Use the shared J1 mapping: Pin1 GND, Pin2 GND, Pin3 3.3 V, Pin4 relay, Pin5 BL0942 via U1‑TX, Pin6 relay, Pin7 BL0942 via U1‑RX, Pin8 BL0942 SCK/line. This enables UART/SPI access for power data. [Elektroda, seeindarkness, post #21771967]
Why does BL0942SPI show bad checksum at 9600/115200?
Users observed repeated "bad checksum" when starting BL0942SPI at 9600 or 115200. It suggests wiring, mode, or clock mismatch, or that a mediator MCU gates traffic. Try verifying the interface mode and lines before debugging firmware. [Elektroda, divadiow, post #21071623]
How can I start trying the BL0942 driver anyway?
From OpenBeken console, run: startdriver bl0942spi 9600. If checksums fail, retry at 115200 and inspect continuity to the BL0942 pins. Quote: "started that ... Warn:EnergyMeter:Failed to read reg" logs confirm attempts. [Elektroda, divadiow, post #21071623]
Is a factory firmware backup available for reference?
Yes. A participant confirmed they backed up the factory firmware and attached it in the thread. This helps recover or analyze Tuya partitions and calibration constants if needed later. [Elektroda, seeindarkness, post #20975197]
What Tuya details are known (model, schema, datapoints)?
The device reports product key s58qrwktuxbbbspj, model SKR, schemaId 000003j6qc. Datapoints include switch_1 (bool), cur_current (0–30000 mA), cur_voltage, cur_power, countdown, and time_total. Logs show SDK build and region endpoints used during activation. [Elektroda, divadiow, post #21069317]
What is OpenBeken and where is this device listed?
OpenBeken is an open firmware for BK7231N devices. The device template was shared and appears in the OpenBeken device list the poster referenced. Use their mapped pins to flash and configure the board quickly. [Elektroda, divadiow, post #21784616]
Any gotchas or edge cases I should expect?
Two common issues: BL0942 checksum failures on both 9600 and 115200, and no output when querying TuyaMCU serial. Both indicate either gated communication or non‑UART paths. Power the board safely and verify pin roles before scripting. [Elektroda, divadiow, post #21071623]
How do I implement a 5–20 minute segmented timer with LEDs?
Use CH10 as a segment counter (0–4). Each button press increments it; map LEDs 1–4 to the count; set coil pulses when CH1 changes; add four 300‑second events to count down. The sample autoexec.bat shows the exact logic. [Elektroda, seeindarkness, post #21771967]
What current can I switch, and any safety advice?
Title and posts refer to a 20 A relay. Use suitable wire gauge, terminals, and enclosure. Latching relays need brief pulses only. Avoid holding a coil on continuously to prevent stress and heating. De‑energize before rewiring. [Elektroda, seeindarkness, post #20967494]
Does the device expose Wi‑Fi and BLE during setup?
Logs show BK7231N Wi‑Fi stack, BLE advertising, and Tuya activation flow. Firmware strings include PROJECT_V1.7_20221027 and device SSID naming, confirming dual‑stack behavior during provisioning. [Elektroda, divadiow, post #21069317]
Quick how‑to: set up the latching relay with auto‑off
- Apply the shared Template: map LEDs, Rel39=pin24, Rel37=pin26, ADC=pin28.
- Paste the 10‑minute script; set Channel1 type to toggle.
- Reboot; press the touch button to toggle ON; it auto‑OFFs after 600 s. [Elektroda, seeindarkness, post #21775536]