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[LN882HKI] Tuya Smart Light disassembly and seek some help to set it up

gregmarfaing 7623 79
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  • #61 21285002
    p.kaczmarek2
    Moderator Smart Home  
    divadiow wrote:
    p.kaczmarek2 wrote:
    There may be still some not added templates in the existing posts.

    probably!

    We would also need to check our ESP devices teardowns. They should be on Teardowns List as well, but they are often not added there due to the lack of time.

    divadiow wrote:

    p.kaczmarek2 wrote:
    Internal temperature?

    must be? I wonder how the power management differs to OBK code, what powersave level is used.

    I wonder if we could try to compare the heating before and after flashing. Is OBK more or less efficient in that manner? Still, this would require a good measurement method. @DeDaMrAz has thermal camera that could do it.

    I already know that in case of BK7231 devices the heating after flashing can be increased if you don't also enable PowerSave. Still, for now, PowerSave is not enabled by default, because of stability concerns - it seems that PowerSave breaks IR receiving (sending?) and BL0937 measurement.
    Helpful post? Buy me a coffee.
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  • #62 21285197
    divadiow
    Level 36  
    What thermal equipment do you have @DeDaMrAz?
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  • #64 21554929
    spleefer90
    Level 7  
    I have a board very similar to https://www.elektroda.com/rtvforum/topic4037269-30.html#21264807, but this version is marked as 20W (there was also an 18W version, AliExpress) - unsure how truthful those numbers are.

    I unfortunately bent the coil(?) and only later realized I can probably poke it out through the two holes on the inside... how do you otherwise remove that without damaging it, it seems very fragile? I ended up rescrewing it by force which sort of re-threaded it.

    Contacts points are the same as per https://www.elektroda.com/rtvforum/topic4076095.html#21228879

    Note the REVERSED TX/RX:

    U0-TX -> RX
    U0-RX -> TX
    GND -> GND
    3V3 -> 3V3
    P21 -> GND(during boot, to enter flash mode, safe to keep it throughout)

    Taking a backup ran for a short amount of time then crashed:

    ```
    python LN882H_Flash_Dumper.py COM3 backup 0x0200000
    LN882H flash dump tool v1.0
    Loading RAMCode...
    Flash RAMCode loaded OK.
    Dumping flash OTP to backup_otp.bin:
    ....
    complete.
    Dumping flash (size: 0x200000) to backup_flash.bin:
    ...................................................................................................................................................Error: Fail. Command execution error.
    ```

    The OG Python script does not handle errors, I have forked it and gave it some resiliency, now one can actually see progress and it retries on errors -
    https://github.com/C0rn3j/LN822H_dump_tool

    It still crashed at the very end overwriting the FW it had until then, yet to fix that one:

    ```
    .............Traceback (most recent call last):
    File "C:\Users\SadCyclops\Downloads\LN882H_CMD_TOOL\LN882H_Flash_Dumper.py", line 81, in <module>
    read_flash(flash_file, arg_port, flash_size)
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "C:\Users\SadCyclops\Downloads\LN882H_CMD_TOOL\LN882H_Flash_Dumper.py", line 26, in read_flash
    bin = bytearray.fromhex(flash_hex)
    ValueError: non-hexadecimal number found in fromhex() arg at position 23
    ```

    Eventually I got the FW dumped and flashed OpenBeken, re-assembled it, configured Wi-Fi, configured the pinouts and startup command to swap red and blue as per the existing 9W device entry.

    Packaging of Smart Bulb C3009 with information label and a phone image. A person holds a black LED bulb box labeled with a TY-A60-20W-220VB product sticker. A person is holding a box of an RGB smart bulb, showing a colorful bulb graphic and information labels. Disassembled LED light bulb parts on a black table. A white LED light bulb with technical information printed on it, held in a hand. Round LED PCB with colorful LEDs and electronic chip. Green PCB with visible traces, pads, pin labels, and a drop of white adhesive or resin in the top right corner. The image shows a printed circuit board (PCB) with various electronic components including capacitors, resistors, coils, and integrated circuits. Section of a printed circuit board with visible capacitors, coil, quartz crystal, and an integrated circuit. Top view of the inside of a kitchen foil roll held by a hand.
    Attachments:
  • #65 21650547
    p.kaczmarek2
    Moderator Smart Home  
    divadiow wrote:

    I think I need to limit brightness maximum because, I don't know about you, but the CPU temp did hit 100 degrees C on mine and the chip hung.

    I've flashed mine today and got the same problem.
    A red-glowing LED bulb next to a smartphone displaying a Wi-Fi control interface for device OpenLN882H.
    Same I2C chip, same LED map. Hit 100C with bulb on quickly.

    @divadiow on which current value did you settle?
    Helpful post? Buy me a coffee.
  • #66 21650550
    divadiow
    Level 36  
    oh! I'll dig it out. I even bought little heatsinks to see if I could make it stable. I think I stopped trying.
    Will report back.
  • #67 21650555
    p.kaczmarek2
    Moderator Smart Home  
    It is stable with lower brightness and dome removed:
    Screenshot of the LED controller OpenLN882H_C25E1088 web interface with brightness, color, and temperature controls plus diagnostic data.
    I am testing lowest current:
    Code: text Expand Select all Copy to clipboard
    
BP5758D_Current 1 1


    Added after 1 [minutes]:

    Another thing is that we always interfere with cooling structure by removing glue...
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  • #68 21650558
    divadiow
    Level 36  
    hmm. nope it got harvested for the BP5758. LN882H module is loose in module box
    Small electronic module with an aluminum heatsink on a blue work surface.

    Added after 44 [seconds]:

    p.kaczmarek2 wrote:
    Another thing is that we always interfere with cooling structure by removing glue...

    true that

    Added after 6 [minutes]:

    actually. I have one of these, https://www.elektroda.com/rtvforum/topic4076095.html#21228879

    no factory heat dissipation measures


    Close-up of a PCB with electrolytic capacitors, resistors, an inductor, and an integrated circuit.
  • #69 21650565
    p.kaczmarek2
    Moderator Smart Home  
    For me it seems stable at 73 degrees with:
    Code: text Expand Select all Copy to clipboard
    
BP5758D_Current 1 1

    Still, this is lower brigthness than in factory firmware. I will try higher current.,

    Added after 39 [seconds]:

    I wonder if drilling some little holes in dome could help...
    Helpful post? Buy me a coffee.
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  • #70 21650568
    divadiow
    Level 36  
    makes you wonder though, what's different with powersave in factory fw to make it run cooler, assuming it does

    Added after 6 [minutes]:

    something special to Tuya SDK? dunno

    Screenshot of a C header file showing definitions for ultra low power sleep mode in an embedded system.

    Added after 3 [minutes]:

    Tuya ln_pm.h
    Screenshot of C header file code named ln_pm.h with sleep mode definitions.

    but also seen in https://github.com/openshwprojects/OpenLN882H/blob/master/components/utils/power_mgmt/ln_pm.h

    Added after 2 [minutes]:

    https://www.elektroda.com/rtvforum/topic4028087-60.html#21018608

    Added after 4 [minutes]:

    https://github.com/openshwprojects/OpenBK7231T_App/blob/main/src/cmnds/cmd_main.c#L98
  • #71 21650616
    p.kaczmarek2
    Moderator Smart Home  
    Nah, I don't think it's powersave. I think the default BP5758 current in OBK is higher than current used by these bulbs, that's why they are hot by default.
    Helpful post? Buy me a coffee.
  • #72 21650625
    insmod
    Level 28  
    Default current in OBK is 14ma, but 10 is good even for GU10 bulbs.
    I've about 10 of them, all with ESP32-C2 with ESPHome. Temperature goes up to about 80 °C.
    LN882H is just very hot by itself.
  • #73 21653592
    divadiow
    Level 36  
    BP5758 LN882H CozyLife just arrived with as-yet unknown PCB (maybe). Maybe this one can be tamed

    Smart B22 LED bulb box with product and distributor label Close-up of BP5758 chip and LEDs on a PCB module Close-up of a circular LED PCB with SMD diodes and electronic components
  • #74 21653821
    p.kaczmarek2
    Moderator Smart Home  
    Hm interesting, looks like LN882H is directly on the main board, with no extra module. Let's hope that pads for flashing are routed out.

    I somewhat remember flashing similar device, I didn't have to remove the screw in this case. It should be described in one of my teardowns.

    I am still preparing myself for DDP animation demo, so i also need to look into my bulbs.
    Helpful post? Buy me a coffee.
  • #75 21653825
    divadiow
    Level 36  
    p.kaczmarek2 wrote:
    Let's hope that pads for flashing are routed out.

    indeed they are

    https://www.elektroda.com/rtvforum/topic4137054.html

    Added after 38 [minutes]:

    Code: Text
    Log in, to see the code


    holding steady around this temperature. full brightness for 2 hours - current limited to 10. not a hot day but not cold either, moderate.
  • #76 21712707
    srisawatsurasak
    Level 2  
    >>21280147
    I used model W509Z2 rgb cct bulb.
    How can I see that the model is W509Z2 ?
    #############################
    Code: JSON
    Log in, to see the code

    ##################################
  • #77 21712731
    divadiow
    Level 36  
    srisawatsurasak wrote:
    How can I see that the model is W509Z2 ?

    It would be labelled as this when pairing with Tuya app. If you have factory flash backup I can flash and confirm for you
  • #78 21712745
    srisawatsurasak
    Level 2  
    >>21712731
    Yes, I have original factory backup.
  • #80 21712755
    srisawatsurasak
    Level 2  
    >>21712747
    Thank you.
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Topic summary

The discussion centers on disassembling and setting up a Tuya-based RGB smart light bulb featuring the LN882HKI chip and a BP5758D LED driver. Initial disassembly was straightforward, and the user successfully backed up the chip firmware and flashed OpenBK (OBK) firmware at 115200 baud after failed attempts at higher speeds. Challenges included identifying correct GPIO pins for PWM control and interfacing with the BP5758D chip, which requires proper SDA and SCL pin mapping. Continuity testing with a multimeter was advised but caused device damage when performed on a powered device. Contributors developed and shared device templates and firmware patches to enable BP5758D driver support on LN882H-based bulbs, including pin mappings and LED channel configurations (e.g., "BP5758D_Map 3 4 2 0 1" and "2 1 0 3 4"). Thermal management issues were noted, with CPU temperatures reaching up to 100°C at full brightness, prompting recommendations to limit brightness and use BP5758D_Current commands to reduce power. Stability concerns remain, especially with MQTT and RGB loops causing disconnections. Firmware dumping tools and flashing procedures were discussed, including correct wiring for UART pins (notably reversed TX/RX lines) and boot mode pin grounding (P21/A9). The community shared resources such as firmware repositories, device templates, and documentation links to assist with flashing, configuration, and troubleshooting. The final confirmed device model is W509Z2, a 220V 9W E27 ES RGB+CCT bulb with LN882H chip and BP5758D LED driver. The discussion also touched on thermal imaging equipment for temperature assessment and comparisons of power management between original and custom firmware.
Summary generated by the language model.
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