[BK7238] Farylink wifi-wsd - OpenBeken CHT8310 on Software I2C P24/P9

Hello everyone!

I recently bought a generic Tuya Temperature and Humidity sensor (Label: wifi-wsd, Manufacturer: Farylink). I decided to do a teardown and flash it with OpenBeken.

Inside, I found a BK7238 Wi-Fi module and a CHT83XX (CHT8310) temperature and humidity sensor.

The Challenge: At first, the I2C pins were completely unknown. Furthermore, it turns out that ESPHome is not a viable option for this specific board design because Tuya wired the sensor to pins P9 and P24. On the BK7231 architecture, these pins do not support Hardware I2C, and ESPHome lacks a native Software I2C implementation.

The Solution: Thankfully, OpenBeken handles Software I2C flawlessly! Since the pins were undocumented, we ended up programming a new brute-force tool called SuperScanner (which we just submitted as a PR to the official drv_multiPinI2CScanner.c!).

Using the scanner, we successfully brute-forced the pinout and found the hidden I2C lines:

SDA: P24
SCL (SCK): P9
Power Pin: None required for this specific board.
Once the pins were mapped, the CHT83XX driver worked instantly.

Here is the JSON template for the auto-importer bot:

json


{
"vendor": "Tuya",
"bDetailed": "0",
"name": "Farylink Tuya WiFi Temperature & Humidity Sensor",
"model": "wifi-wsd",
"chip": "BK7238",
"board": "Generic",
"flags": "1024",
"keywords": [
"Temperature",
"Humidity",
"CHT83XX",
"Farylink"
],
"pins": {
"9": "CHT83XX_SCK;0;0",
"24": "CHT83XX_SDA;1;2"
},
"command": "backlog PowerSave 1; startDriver CHT83XX; setChannelType 1 Temperature; setChannelType 2 Humidity",
"image": "https://obrazki.elektroda.pl/YOUR_IMAGE.jpg",
"wiki": "https://www.elektroda.com/rtvforum/topic_YOUR_TOPIC.html"
}
I have attached some high-resolution pictures of the casing (including the Farylink sticker) and both sides of the PCB below for reference.

I hope this helps anyone else trying to liberate this specific Tuya sensor! Let me know if you have any questions.

cool, but was the config not extractable from the Tuya config using Easy Flasher and a backup of the original flash?

>>21935209

Unfortunately not. I flashed the device before making a backup of the original Tuya firmware, so I no longer had access to the Tuya configuration data.

At the time I wasn't expecting to need the original pin mapping, so I ended up reverse-engineering it instead. Since the I2C pins were unknown, I wrote (AI assisted) a brute-force I2C scanner (now submitted as a PR to OpenBeken) to test every possible pin combination until I found the correct mapping:

SDA: P24
SCL: P9

In the end it worked out well, and the scanner may also help identify undocumented I2C devices on other BK72xx boards.

I suppose that's the classic rookie mistake: flash first, ask questions later! 😄

ah sure. depending on which tool you used to flash and if you erased first, the Tuya config may still be present and usable. There's also the question of your button and LED on that device. After OBK conversion the Tuya config can be saved to a small file (if it still exists) and fed into the Tuay config extractor in EF.

>>21935226
Thanks a lot, I'll try and post the result.

>>21935229

here is it, thanks a lot!

Other PINs of this chip:

P6 (PWM0)   WifiLED
P23  Btn