FAQ
TL;DR: A 100–200 ms pulse is enough to flip the MD7620 latching relay, and “Bridge driver will start automatically after reboot” [Elektroda, valeklubomir, post #20448030] OpenBK v1.17.441 adds native Bridge support and fixes over-heating caused by continuous coil drive [Elektroda, robert21965, post #20942245]
Why it matters: Correct pin roles and pulse timing stop the relay from drawing >2 W as heat and extend module life.
Quick Facts
• Wi-Fi SoC: Beken BK7231N, 32-bit, 2.4 GHz [Elektroda, valeklubomir, post #20288620]
• Relay driver: MD7620 H-bridge, 100–200 ms activation pulse [Elektroda, valeklubomir, post #20288620]
• Metering IC: BL0942, ±1 % typical after calibration [Elektroda, valeklubomir, post #20288620]
• Latest tested OpenBK: v1.17.441 (Jan 2024) [Elektroda, robert21965, post #20942245]
• Flash speed: 921 600 bps UART; HID tool removes 100-attempt issue [Elektroda, romanfarki, post #20476727]
Which GPIO pins control the Tongou TO-Q-SY1-JWT?
P9 – status LED, P15 – Wi-Fi LED, P17 – push-button, P24 – BridgeFWD, P26 – BridgeREV [Elektroda, valeklubomir, post #20288620]
How do I enable the H-bridge driver in OpenBK?
- Set P24 to BridgeFWD;1 and P26 to BridgeREV;1. 2. Reboot so the Bridge driver autostarts. 3. If 0 drivers show, issue startDriver Bridge once [Elektroda, Osrx, post #20863693]
My relay stays energised and overheats—why?
Using Rel/Rel_n roles powers the coil continuously. Switch to BridgeFWD/BridgeREV roles so the driver sends a 100–200 ms pulse only [Elektroda, przemsi_ele, post #20862770]
How can I lengthen or shorten the relay pulse?
After the Bridge driver is running, send BridgePulseLength ; values between 80 and 250 ms are typical [Elektroda, p.kaczmarek2, post #20862439]
Can I flash a CBU module without desoldering?
Yes. Solder 4–5 dupont wires (3V3, GND, RX, TX, CEN) on-board, hold CEN low, and flash with BK7231GUIFlashTool or hid_download_py [Elektroda, p.kaczmarek2, post #20797962]
Serial flashing stalls at 100 attempts—fix?
Use the HID USB downloader; users report write time dropping from 30 minutes to <2 minutes [Elektroda, p.kaczmarek2, post #20476735]
Why does power read 3–4 W with no load?
Zero-offset is needed. Run SetupEnergyStats or enable flag 38 to auto-zero when relay is off [Elektroda, p.kaczmarek2, post #20935400]
How do I calibrate BL0942 measurements?
Supply a known resistive load, then issue EnergyCal Voltage , Current , Power . Repeat until readings match within ±1 % [Elektroda, robert21965, post #20935273]
Module reboots when measuring solar inverter output—why?
Negative current can exceed firmware assumptions and trip a watchdog, causing resets [Elektroda, thealphahelix, post #20475897] Bridge to a conventional load during testing.
What’s the longest reported OpenBK uptime?
Test lamps ran for almost 90 days without reboot [Elektroda, p.kaczmarek2, post #20449965]
How do I change the power-on state of relay and LED?
Open Configure Startup, set Channel 1 to –1 (restore last), 0 (off) or 1 (on); LED follows the relay channel [Elektroda, windo31, post #21591074]
P24 pad lifted—can I use another pin?
Yes. Map an unused GPIO such as P6 to BridgeFWD and pair it with P26 BridgeREV; keep Channel IDs identical [Elektroda, romanfarki, post #20474690]
Does OpenBK support SSDP for Windows discovery?
Run startDriver SSDP once; the switch appears under ‘Network’ in Explorer [Elektroda, p.kaczmarek2, post #20449965]
Edge case: driver not autostarting after reboot?
Check that autostart flag isn’t cleared. If needed, add startDriver Bridge to autoexec.bat [Elektroda, p.kaczmarek2, post #20862565]
Three-step flashing recap
- Hold CEN low and power the board.
- Run BK7231GUIFlashTool, select OpenBK .bin, click Flash.
- Release CEN; connect to the new Wi-Fi AP to finish setup [Elektroda, p.kaczmarek2, post #20797962]
