Getting Tasmota on a generic smart bulb

Hardware
1

I picked up some cheap(ish) RBG lamps off of Amazon (https://www.amazon.com/gp/product/B07WGL5L8Q) and am trying to get Tasmota or ESPHome loaded on them. They don’t work with tuya-convert, it looks like they came with the newer firmware that isn’t compatible. I’m seeing the same issue that’s described here: https://github.com/ct-Open-Source/tuya-convert/issues/483

So, it looks I’m going to have to go the hardware flash route. It should be straight-forward, but I’m stuck on one thing – I can’t find a place to pick up ground! There are convenient pads labeled 3.3V, RXD, TXD, and RST, but without tearing the lamp down the rest of the way I haven’t found anything else. My real hope was that the 8-pin connector going to the LED board would work, but I think that is just powering the LEDs (although there has to be a ground connection on there somewhere).

Before I try and tear one of these apart the rest of the way, has anyone either successfully flashed a bulb like it or have any other suggestions?

Here are some pics:

IMG_7857.HEIC
IMG_7857.HEIC3012×2543 1.29 MB
IMG_7856.HEIC
IMG_7856.HEIC2671×3022 1.31 MB
IMG_7855.HEIC
IMG_7855.HEIC3019×3009 1.6 MB
IMG_7854.HEIC
IMG_7854.HEIC2543×2565 1.58 MB
IMG_7853.HEIC
IMG_7853.HEIC2452×2459 1.57 MB
IMG_7852.HEIC
IMG_7852.HEIC2673×2560 1.14 MB

2

One bit of good news – I found ground! You can just barely see it on the picture of the internals, it’s down at the bottom of the white board above the capacitor. And with a bit of work with a multimeter, I found it on one of the pins on the 8-pin connector, the 2nd from the lower left as you look at the LED side of the board above. It doesn’t look like any of the others make it to that connector though.

I have an FTDI adaptor on order that should be here Saturday (my current one will only deliver 5V), I’ll see if esptool can backup the current firmware, or if I’m out of luck on these bulbs.

3

If anyone else is following along, no luck with these bulbs so far. I’m going to have to tear one down and see what chip they are built on. Even with a hard-wired serial connection and the RST pin tied to ground, esptool hasn’t been able to talk to the bulb successfully.

UPDATE: they are an ESP8266, so no idea why it won’t return any info from esptool…