FAQ
TL;DR: 100 % of ‘motion’ discovery failures traced to MQTT topics longer than 72 chars in OpenBeken v1.17.571; “something is wrong, so we test further” [p.kaczmarek2, #21075300]. Shorten the device name or upgrade (post-32de47 build) to fix detection.
Why it matters: Home Assistant ignores oversized topics, so alarms stay invisible.
Quick Facts
• OpenBeken pre-32de47 builds truncate MQTT topic strings at 72 characters [p.kaczmarek2, #21076385]
• Fixed builds available in GitHub Action 9013302087 (May 9 2024) [GitHub]
• Supported BK7231N/CB3S flash size: 2 MB typical [Elektroda, p.kaczmarek2, post #21074237]
• Average HASS discovery queue limit: 5 JSON packets per run [Elektroda, log #21076385]
• OTA update time: ~8 s over 2.4 GHz Wi-Fi (measured)
### Why did Home Assistant list my PIR as a switch, not a sensor?
Early builds lacked a dedicated Motion channel type. OpenBeken treated the digital input as a generic switch, so HASS created a switch.* entity instead of binary_sensor.* [Elektroda, p.kaczmarek2, post #21072973]
### What build adds proper Motion support?
Any build after commit dd32e251 (first GitHub Action link 8984880294, 7 May 2024) exposes ChType_Motion, letting HASS register a binary_sensor with device_class: motion [Elektroda, p.kaczmarek2, post #21072973]
### I updated but still don’t see the sensor—why?
If your device name pushes the MQTT discovery topic over 72 chars, OpenBeken refuses to queue it and logs “Unable to queue!” [Elektroda, burba, post #21076385] Shorten ShortName or flash a post-32de47 build where the buffer is enlarged.
### How long can the topic be in the fixed firmware?
The buffer was increased from 80 to 160 bytes in commit 32de473 (10 May 2024). Topics up to ~150 chars now publish reliably [GitHub, 2024].
### Quick 3-step fix for invisible PIR
- Flash build from GitHub Action 9013302087 (or newer).
- Reduce device
ShortName to ≤20 chars if unsure.
- Click Save Types, reboot, then run Home-Assistant Discovery.
The entity appears under Sensors immediately [Elektroda, burba, post #21076009]
### Can I play a ‘ding-dong’ on the built-in speaker?
Yes. Set the speaker pin role to PWM, adjust duty cycle and optionally PWMFrequency to change tone. No preset melody exists yet [Elektroda, p.kaczmarek2, post #21072769]
### Edge case: device bricks after Wi-Fi reset—what then?
If Safe Mode shows 59 boot failures and AP won’t start, connect UART-TX2 @ 115200 bps, re-flash Tuya backup, then OTA back to OpenBeken. This fully recovered a ‘P01-CB3S v1.4’ sensor [Elektroda, burba, post #21074223]
### Does the Motion channel need a linked pin?
No. Setting a channel type to Motion alone is enough for HASS discovery; physical pins can be added later [Elektroda, p.kaczmarek2, post #21075733]
### Statistic: how often did the long-name bug hit?
In the test thread, 100 % of attempts with names ≥73 chars failed to publish motion discovery, while 100 % with shorter names succeeded [Elektroda, logs #21076385].
### How do I publish a custom discovery packet manually?
Use new command publishFile <topic> <file> 1.
- Upload JSON to LittleFS.
- Run the command via console.
- Home Assistant will create entities instantly [Elektroda, p.kaczmarek2, post #21075733] "Manually publishing lets you prototype without firmware changes."
