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]
Comments
Thank you so much presentation! I would like to send you free elektroda.com gadgets, could you provide your address in the Private Message? [Read more]
"The firmware do not support the bridge driver MD7620 yet, but the work is in progress." Hi! Any screw? [Read more]
I think @valeklubomir has it implemented on his branch, but the pull request wasn't created yet. [Read more]
Valek submitted PR, driver will be added today! Thank you! [Read more]
Hey, I'm new to the forums and I have one of these I'm trying to configure. I've flashed the firmware over and it's working fine, but I'm now trying to work out the pin configuration... Is there a procedure... [Read more]
Hello For the basic functionality it is enough just to setup pins. Bridge driver will start automatically after reboot. https://obrazki.elektroda.pl/2975965200_1676854866_thumb.jpg BridgeFWD... [Read more]
Heroic! Thanks so much, I got this working today :) I can't believe how smooth this process was. [Read more]
Valek did very good job with the driver. Btw @thealphahelix , have you tried "startDriver SSDP"? Device will show up in Windows: https://obrazki.elektroda.pl/2386696800_1676940525_thumb.jpg btw2... [Read more]
What? That's awesome! I'll be trying that too :) Thanks so much for the platform and all the help. [Read more]
i have sucesfuly flash to this device but the relay dont switch https://prnt.sc/mz2QWHowVvMA https://obrazki.elektroda.pl/4923590600_1678210948_thumb.jpg here is config : somthing i need to... [Read more]
You have attached images incorrectly. External links will expire over time. Please use our image hosting. I have already fixed your post, but keep it in mind. Why do you have a Rel_n configured? Are... [Read more]
i will only let know what was my problem : i solved it right now be desoldering the chip i have brake P24 pad also i connected it now - i have change to P6 (PWM0) it was near and soldered with... [Read more]
What kind of desoldering method did you use? We will be publishing a hot air tutorial for IoT hacking soon. Please subscribe to our channel so you can see how to easily desolder the module. https:... [Read more]
i have used a hot gun, but not much practice, like you see :) now is second done, but why the programer needs 100 atempts to write sucesfully ? https://obrazki.elektroda.pl/3475865100_1678219261_thumb.jpg... [Read more]
What kind of USB to UART converter do you have? For me it works good. Maybe not enough flux when soldering? Did you first add Pb solder to make joints melting point lower? [Read more]
i use this one https://obrazki.elektroda.pl/3877858800_1678222004_thumb.jpg no i used only gun temperature 330 Celsius but second i have make on board , i solder there only 5 wires _... [Read more]
I don't know this board, it may be low quality or something, or more sensitive to noise. Using just hot gun for desoldering makes the job very hard. I think you should first apply flux, then apply Pb... [Read more]
To check in on this thread, we had an issue where the module kept turning itself off - not sure what was causing that. We were using it to run a solar inverter output through to measure it, so that may... [Read more]
today i have flashed 2 more cb2s chips but not work on first time at all see picture :) https://obrazki.elektroda.pl/2412173500_1678299971_thumb.jpg https://obrazki.elektroda.pl/2984459100_1678299975_thumb.jpg... [Read more]