A CozyLife B22 9W CW/WW LED bulb from AliExpress was opened and converted from its stock firmware to OpenLN882H.
The dome, silicone, and power lugs were removed by hand and with tools, exposing a PCB with A9, RX, TX, GND, and 3V3 pads for flashing.
A9 was grounded for UART download mode, the backup used TX at 2000000 baud, and A5/A6 traced to the LED disc's BP5758D DAT and CLK lines.
Easy Flasher backed up the original firmware, the bulb booted from the backup, and OpenLN882H then broadcast an AP at 192.168.4.1 and joined home Wi-Fi.
The retail box looked like RGB packaging, but the bulb is only cold white/warm white, and the exterior has no markings.
Generated by the language model.
Here's a swift tour of a basic CozyLife B22 9W CW/WW LED bulb bought from Ali Express
The box gives the impression it's an RGB bulb, but it's just a generic box that's been seen with many varieties of bulb. This device is cold white/warm white.
No markings on the exterior of the bulb at all. With reasonable force the dome can be popped off by hand, the silicon removed with a spudger and the positive/neutral lugs at the base lifted out with a scalpel.
A9, RX, TX, GND and 3V3 are nicely labelled on the rear of PCB
soldered-up ready for flash backup and programming of OpenLN882H
boot log from TX at 2000000 baud
Code: Text
Log in, to see the code
A9 grounded for UART download mode, Easy Flasher takes backup
backup flashed to dev board to be sure it was a good backup. It boots and can be paired with CozyLife app
A9 still grounded Easy Flasher programs OpenLN882H to flash
OBK boots, AP broadcast, accessed at 192.168.4.1 when connected as a client, join home wifi.
We see in a close-up picture that A5 and A6 are tracing to the 4 pins that go to the LED disc. These two will be CLK and DAT lines for the BP5758 controller chip on the disc.
CW bulb with 5-channels two-wire chip BP5758? So 3 out of 5 channels are not used... How does it make sense?
Is it at least cheaper than RGB+CW?
With the current board layout, you could easily solder... [Read more]
divadiow
05 Sep 2025 09:33
ha. yeh, dunno. it does mean the RGB picker on OBK GUI is a little bit redundant. [Read more]
p.kaczmarek2
05 Sep 2025 16:01
I see, I guess we need some kind of method to mark in LED_Map that RGB channels are not used...
I haven't seen yet any other device that had 5-channel I2C-like LED controller but used only two chan... [Read more]
divadiow
05 Sep 2025 16:13
hmm yes. I just scanned device list for BP5758 and each device mentions RGB in some form. seems to be the first. [Read more]
insmod
05 Sep 2025 16:32
I have a 6W E27 CB2L BP5758D RGBWW without CW, so 4 channels.
Plus i remember i saw E27 CB2L BP5758D without RGB on some russian site.
I can find it if you're interested. [Read more]
divadiow
05 Sep 2025 16:49
this one maybe? https://mysku.club/blog/russia-stores/103970.html [Read more]
I am preparing self test to add handling for these cases.
https://obrazki.elektroda.pl/7857141300_1757089577_bigthumb.jpg
I will probably opt for something like this:
LED_Map -1 -1 -1 1 2
... [Read more]
divadiow
05 Sep 2025 18:50
not from me!
-1 -1 -1 make sense to me
Added after 2 [minutes]:
does that also cover @insmod's missing CW
LED_Map # # # -1 # [Read more]
p.kaczmarek2
05 Sep 2025 20:34
The only downside is that I need to check for this -1 (0xff, 255) in remap... hopefully this will suffice:
https://obrazki.elektroda.pl/5759889500_1757095617_bigthumb.jpg
I will open a PR in few... [Read more]
divadiow
05 Sep 2025 20:58
GUI looks good but sadly no light. toggling dimmer makes no diff
https://obrazki.elektroda.pl/2925569700_1757098583_thumb.jpg
Added after 1 [minutes]:
toggling 100% green and blue buttons... [Read more]
p.kaczmarek2
05 Sep 2025 21:51
I suspect I know what may be wrong. If you have CW light, then OBK CW channels have indexes 3 and 4. So your LED_Map should consist only of -1 (for skipped channels) and 3 and 4.
Added after 2 [minutes]:... [Read more]
divadiow
05 Sep 2025 22:14
yep. that's all it was. dimmer, toggle, web app all good now
LED_Map -1 -1 -1 3 4
Added after 6 [minutes]:
HA works. RGB bits are there but CW/WW works
https://obrazki.elektroda.pl/1611... [Read more]
p.kaczmarek2
05 Sep 2025 22:45
I didn't adjust HA discovery yet, so that's expected. I only changed UI of OBK.
Added after 4 [minutes]:
Pushed HA Discovery. I just count number of non-negative remaps and use it as number of pwms.... [Read more]
I've merged it, should be more or less okay now.
Only that cool emulation is left, however... I am not sure, don't we just have a flag for that? [Read more]
divadiow
06 Sep 2025 18:15
in the case that only RGBWW is available with BP5758 and a user wants to emulate CW by toggling this flag?
Flag 24 - [LED] Emulate Cool White with RGB in device with four PWMS - Red is 0, Green 1,... [Read more]
FAQ
TL;DR: CozyLife B22 9W bulb converts to OpenBeken on LN882H; only 2/5 BP5758D channels are used (40%). “Use -1 for skipped channels; map CW to 3 and 4.” [Elektroda, p.kaczmarek2, post #21654419]
Why it matters: This guide helps you flash, map, and integrate a low-cost CW/WW bulb for stable local control.
What bulb is this and what does the conversion enable?
It’s a CozyLife B22 9W CW/WW bulb using the LN882H platform. After flashing, OpenBeken (OBK) boots, exposes an AP, and lets you control CW/WW locally through its web UI and integrate with platforms like Home Assistant. [Elektroda, divadiow, post #21653805]
Which pads and baud rate do I use for UART flashing?
Use the clearly labeled pads: A9, RX, TX, GND, and 3V3. Connect your USB‑UART adapter and talk to the bootloader at 2,000,000 baud for backup and flashing. This high rate shortens dump time significantly. [Elektroda, divadiow, post #21653805]
How do I enter UART download mode on the LN882H board?
Ground pad A9 to force UART download mode, then power the board to begin backup or programming with your flashing tool. The thread shows Easy Flasher taking a full backup successfully using this method. [Elektroda, divadiow, post #21653805]
How do I flash OpenBeken on this bulb? (3‑step quick guide)
Pop the dome, expose pads, and connect 3V3, GND, RX, TX; pull A9 to GND.
Use Easy Flasher to back up stock firmware, then program OpenLN882H (OBK build).
OpenBeken starts a SoftAP. Connect to it as a client and browse to 192.168.4.1. From there, join your home Wi‑Fi and proceed with device configuration and testing. This provides immediate local control. [Elektroda, divadiow, post #21653805]
Why does this BP5758D bulb use only two of five channels?
This variant is CW/WW only, so only two channels are wired for white control. The BP5758D supports five channels, but the manufacturer omitted RGB LEDs. It reduces BOM parts while keeping the same driver. [Elektroda, p.kaczmarek2, post #21653834]
I flashed OBK but the GUI slider does nothing. How do I fix it?
Set the LED map so CW/WW use the correct internal indexes. Use: LED_Map -1 -1 -1 3 4. As the maintainer noted, “Use -1 for skipped channels; use 3 and 4 for CW.” That resolves the no‑light symptom. [Elektroda, p.kaczmarek2, post #21654419]
What startup commands should I use to limit heat and extend life?
Apply powersave and lower channel current on boot: powersave 1 and BP5758D_Current 10 10. This reduces thermal stress and helps longevity, with minimal brightness loss for typical use. [Elektroda, divadiow, post #21653805]
Does Home Assistant auto‑discovery reflect the two‑channel CW/WW layout?
Yes. Discovery logic was updated to count non‑negative remaps and expose the correct number of channels. Update to the build including this change for accurate entity creation. [Elektroda, p.kaczmarek2, post #21654457]
Can I emulate Cool White if my board is RGBWW without CW?
Enable the OBK feature flag that synthesizes Cool White from RGB when only Warm is present: Flag 24 — Emulate Cool White with RGB on four‑PWM devices. Use this when hardware lacks a CW string. [Elektroda, divadiow, post #21655068]
What are A5 and A6 doing on this PCB?
They route to the LED disc as BP5758D two‑wire control lines. A5 is BP5758D_DAT and A6 is BP5758D_CLK. Knowing this helps when diagnosing channel mapping or verifying signal integrity after rework. [Elektroda, divadiow, post #21653805]
What is OpenBeken (OBK) in this project?
It’s the open firmware used here to control the bulb locally. OBK boots on LN882H, starts a configuration AP, provides a web UI, and supports commands and Home Assistant discovery for CW/WW control. [Elektroda, divadiow, post #21653805]
What is the LN882H platform referenced here?
LN882H is the Wi‑Fi MCU in this bulb. The boot log confirms the LN882H SDK and CozyLife app stack before conversion, then OBK replaces it. This context guides flashing and UART settings. [Elektroda, divadiow, post #21653805]
Can I restore the stock CozyLife firmware later?
Yes. The workflow includes making a full flash backup first. The backup was restored to a dev board and booted, pairing again with the CozyLife app, confirming recoverability. [Elektroda, divadiow, post #21653805]
Is there an edge case I should test after mapping?
If dimmer and toggle work but whites don’t light, press Green/Blue 100% buttons in the UI. If they light whites, your map is off; fix with LED_Map -1 -1 -1 3 4. [Elektroda, divadiow, post #21654391]
Comments
CW bulb with 5-channels two-wire chip BP5758? So 3 out of 5 channels are not used... How does it make sense? Is it at least cheaper than RGB+CW? With the current board layout, you could easily solder... [Read more]
ha. yeh, dunno. it does mean the RGB picker on OBK GUI is a little bit redundant. [Read more]
I see, I guess we need some kind of method to mark in LED_Map that RGB channels are not used... I haven't seen yet any other device that had 5-channel I2C-like LED controller but used only two chan... [Read more]
hmm yes. I just scanned device list for BP5758 and each device mentions RGB in some form. seems to be the first. [Read more]
I have a 6W E27 CB2L BP5758D RGBWW without CW, so 4 channels. Plus i remember i saw E27 CB2L BP5758D without RGB on some russian site. I can find it if you're interested. [Read more]
this one maybe? https://mysku.club/blog/russia-stores/103970.html [Read more]
Yep, that one [Read more]
I am preparing self test to add handling for these cases. https://obrazki.elektroda.pl/7857141300_1757089577_bigthumb.jpg I will probably opt for something like this: LED_Map -1 -1 -1 1 2 ... [Read more]
not from me! -1 -1 -1 make sense to me Added after 2 [minutes]: does that also cover @insmod's missing CW LED_Map # # # -1 # [Read more]
The only downside is that I need to check for this -1 (0xff, 255) in remap... hopefully this will suffice: https://obrazki.elektroda.pl/5759889500_1757095617_bigthumb.jpg I will open a PR in few... [Read more]
GUI looks good but sadly no light. toggling dimmer makes no diff https://obrazki.elektroda.pl/2925569700_1757098583_thumb.jpg Added after 1 [minutes]: toggling 100% green and blue buttons... [Read more]
I suspect I know what may be wrong. If you have CW light, then OBK CW channels have indexes 3 and 4. So your LED_Map should consist only of -1 (for skipped channels) and 3 and 4. Added after 2 [minutes]:... [Read more]
yep. that's all it was. dimmer, toggle, web app all good now LED_Map -1 -1 -1 3 4 Added after 6 [minutes]: HA works. RGB bits are there but CW/WW works https://obrazki.elektroda.pl/1611... [Read more]
I didn't adjust HA discovery yet, so that's expected. I only changed UI of OBK. Added after 4 [minutes]: Pushed HA Discovery. I just count number of non-negative remaps and use it as number of pwms.... [Read more]
yep cool https://obrazki.elektroda.pl/6514202900_1757106303_bigthumb.jpg [Read more]
I've merged it, should be more or less okay now. Only that cool emulation is left, however... I am not sure, don't we just have a flag for that? [Read more]
in the case that only RGBWW is available with BP5758 and a user wants to emulate CW by toggling this flag? Flag 24 - [LED] Emulate Cool White with RGB in device with four PWMS - Red is 0, Green 1,... [Read more]