FAQ
TL;DR: 3.3 V at 250 mA powering the CBU gave 5 / 5 successful UART flashes [Elektroda, Digga, post #20453437]; “SPI finally works” [Elektroda, p.kaczmarek2, post #20478455] OpenBK now supports BL0942 over SPI, no board cuts required.
Why it matters: DIY installers can now get live energy data without hardware surgery.
Quick Facts
• Module: BK7231N-CBU with internal CT; Wi-Fi 2.4 GHz, 1 MB flash [Elektroda, TurkeyMan, post #20361991]
• Meter IC: BL0942, 24-bit ADC, 0.1 % typ. accuracy (datasheet)
• Flashing voltage: 3.3 V ± 0.1 V, ≥250 mA recommended [Elektroda, Digga, post #20453437]
• Supported firmware: OpenBK ≥ 1.15.453 with BL0942SPI driver [Elektroda, Digga, post #20507667]
• Typical AliExpress price: US $14–18 (Oct 2023 search)
1. What hardware is inside the PZIOT-E01 energy meter?
The DIN-rail unit contains a BK7231N-CBU Wi-Fi module on a daughterboard and a BL0942 energy-metering IC on the main PCB. Current is sensed by an internal split-core CT wrapped around the through-hole, so no series wiring is needed [Elektroda, TurkeyMan, post #20361991]
2. Can I flash OpenBK without cutting any SPI traces?
Yes. Since build 1.15.453 the BL0942SPI driver supports the original SPI wiring, eliminating the earlier UART reroute hack [Elektroda, Digga, post #20507667]
3. Flashing stops at “Cannot get Bus.” How do I fix it?
Use a solid 3.3 V supply that can source at least 250 mA, connect only TX, RX, GND, then run uartprogram, power the board, and retry 2–3 times; this solved repeated failures for multiple users [Elektroda, Digga, post #20453437] [Elektroda, TurkeyMan, post #20444369]
4. What pins does the firmware use in SPI mode?
Default mapping is P14-CLK, P16-MOSI, P17-MISO, P9-CF1, and a user-selectable CS. These match the factory wiring found in the teardown [Elektroda, TurkeyMan, post #20361991]
5. How accurate is a meter that only loops the neutral conductor?
Accuracy is unchanged because current in the neutral equals line current in single-phase wiring. Error appears only if leakage to earth exceeds a few milliamps, typically < 0.5 % of load [Typical IEC data].
6. Does the unit separate export (solar) and import energy?
The BL0942 registers support signed power, but current OpenBK builds add forward and reverse watt-hours together. Separate counters are on the roadmap [Elektroda, Digga, post #20790506]
7. Can I improve Wi-Fi range with an external antenna?
Only CBU-IPEX modules expose an IPEX socket. The standard CBU has only a PCB pad, so adding a wire antenna is impractical and still unlikely to reach 50 m reliably [Elektroda, p.kaczmarek2, post #20466116]
8. Is Supla firmware available for this platform?
No. Supla targets ESP-based boards; it does not compile for BK7231, so you cannot load native Supla firmware on this meter [Elektroda, p.kaczmarek2, post #21072178]
9. What power source is safe during flashing?
Use a bench supply or CP2102/CH340G adapter feeding 3.3 V directly; avoid powering the 5 V rail on the main PCB to keep surrounding electronics off [Elektroda, TurkeyMan, post #20444369]
10. What edge cases break SPI communication?
Users saw one bit error in five reads until they added a small capacitor on the CLK line; unstable breadboard wiring is the main culprit [Elektroda, p.kaczmarek2, post #20497046]
11. How do I reroute to UART if I still want to?
- Cut two SPI traces. 2. Solder jumpers from BL0942 TX/RX to P16/P17. 3. Enable bl0942 driver in OpenBK. The mod takes about 15 minutes [Elektroda, p.kaczmarek2, post #20362038]
12. Home Assistant can’t see the sensor after update—what now?
Builds before Dec 2023 missed HA discovery for BL0942SPI. Update to the commit dated 02-Dec-2023 or later; discovery packets now advertise correctly [Elektroda, p.kaczmarek2, post #20843006]
13. Can I contribute code or testing?
Yes. Fork the repo, push to your branch, and GitHub Actions will auto-build binaries for you to test. Pull requests are merged once features are functional [Elektroda, p.kaczmarek2, post #20456679]
14. What does flashing over-current do to my USB port?
A large capacitor on the 3.3 V rail can draw more than the USB 500 mA limit at plug-in. Most modern ports shut down, but older hubs may fail, so keep capacitance modest (<470 µF) [Elektroda, p.kaczmarek2, post #20475449]
