I just tried that and it didn’t work. However, I cut the RX trace only on another board and that worked.
Here is what it looks like. You’ll see I nicked the ground plane when cutting the trace, so I’ll have to be careful when soldering so as not to create a short to ground.
Actually in reference to what @plstearns asked, that is the TX trace from the Tuya MCU. Remember TX goes to RX and RX to TX between chips / devices. Either way I guess that answers that question, so thanks for the info! I’ll update my instructions.
Thanks for the clarification. I’m in the part of my life cycle where I don’t have a lot of time to tinker so the info saves me hours of troubleshooting and frustration. 
I’m using Local Tuya also for both Feit dimmers and light bulbs! A very simple process that does not involve messing with internal parts or any soldering. I was able to get about 15 light bulbs and dimmers set up with no problem. But for some reason, I have one dimmer that will not go to 100% brightness. It works on the smart life app but not with Local Tuya. How did you configure yours in local tuya? Thanks for your time!
I’ve done this to two dimmers, and I can’t seem to bridge the connection once cut. I’m using flux and a decent solder. Any tips here? I’ve had to just use a jumper wire once the connection has been severed.
Did you guys figure out the root cause of the flickering and brightness not going to 100 via power or remote? While it show 100 I have to press up one extra time to get full brightness and fix flickering .
I am fiddling with feit support as it looks like a software bug in mcu unit in my opinion.
Any suggestion or comment that I can tell them, like anybody ever looked at signal with oscilloscope?
, I have 2 led lights and single pole.
If it does not take me anywhere I am thinking about connecting the up pin of Macy to esp module and somehow click up 10 time when turning on so mcu fix itself
I never did - and I have a new oddity.
I was playing with flashing Tasmota. Flashed back and forth between Taz and ESPHome several times.
Had a bad flash and ended up having to disconnect the chip from the MCU board and doing a manual reflash. I did not disconnect the power from the MCU - just the data lines.
After reconnecting everything - everything works - but the Low Dim set will not go below 260. If I go into the MCU set mode (hold up and down at the same time for 5 seconds) I can trim all the way down to min setting. But as soon as I exit MCU program mode, it jumps back up to 260.
This is NOT a Taz/ESPHome program problem. Running the same code I’m running on 9 other lights that all work fine.
I am forced to conclude that there is some sort of MCU eeprom setting that I either screwed up or don’t know how to access by software. Maybe I could connect to RX/TX and play around but - I am probably just going to put this in a location that I don’t need dimming but need a 3-way and call it good.
As far as the last click up - never solved. All of mine do it. Flickering seems to be a little bit better with later versions of ESPHome but that may just be me “tuning it out.”
Lastly - I wanted to report that I salvaged two units that I trashed the TYWE2S chip when desoldering. I bought some ESP12Es and was able to successfully “transplant” in a new chip with some very fine gauge wire and a sloppy bit of electrical tape holding the chip inside the black plastic packaging that they shipped in as an insulator. There is plenty of room between the switch face and the MCU board. The 12Es are slightly longer - but that doesn’t matter since the wires are joining the two boards instead of the pads.
If you don’t want to go that route and have bad TWYE2S that need replaced - there is a ready-to-flash substitute that is the same form factor.
https://lcsc.com/product-detail/WiFi-Modules_Wireless-tag-WT-01N_C477823.html
Here is my Frankenstein switch in test. I shortened the wires quite a bit when I did the final assembly.
Sorry I never quite finished the complete flashing newbie guide - but there are plenty of other options out there for how to flash a chip.
So many great options out there besides these switches. The TuyaMCU is a bit of a PITA now that I have played with others. Some nice LINKIND brand switches that come with a very-easy-to-flash ESP32 chip that includes bluetooth! Have been deals for MUCH cheaper than these switches. Switch and Dimmer.
The big positive for these switches is the 3-way and dimmer in the same package. I have quite a few 3 & 4 way applications and these allow me to automate / dim those circuits while leaving mechanical switches in the circuit. Without a 3-way compatible switch, you can still get 3-way functionality by installing two single-pole switches and slaving them together with Tasmota groups (or other automation solutions.)
Good luck and have fun!
PS - if you do a substitution like I did above with a ESP12 series - note that you need to connect VCC to EN (enable the chip) and connect GPIO15 to GND (allow boot). If you zoom in on my photo you can see I just did a small jumper for IO15 to GND and you can see the longer jumper for VCC to EN. Technically there should be a pull-up/pull-down resistor but this seems to be working fine in this application.
Did anybody tried to flash the MCU ? I looked at their manual last night but was not very useful
How did you get the 3/4 way to work once tasmota was flashed. I have it flashed but it stopped working as 3/4 way
I can’t attest to trying 3-way with Tasmota. Dd you try this?
I did try that setting and still only acts like a single pole switch
Well the 3-way function is handled by the TuyaMCU, not the ESP chip / Tasmota. I’ve replaced most of these switches in my house, except for the few that I specifically use for their 3-way function… so I know for a fact that it works just fine. As long as you have everything wired correctly (i.e. have the toggling hot Red connected to the correct Feit dimmer port), it should work.
The only other thing I can think of is the flashing process you used. If you used my method, then perhaps the TuyaMCU TX trace isn’t properly soldered back together? I would assume the switch would still function correctly as a traditional 3-way even with this; however, it would definitely prevent status updates from being sent to the TYWE2S module / ESP chip.
I’m sort of with Technowizard. I am going to use these in a few applications but the TuyaMCU in this build is a little flakey (flickers, hum). Since I have 10 of them - I am going to make them work in certain locations but I’m moving on because of the strange behavior - esepcially with LED lights.
The real solution for 3 way dimming that is the bees knees is to just use a single pole smart dimmer at the LOAD location (can be either end) and then install a cheaper single pole non-dimmer on the opposite end. Both with Tasmota. Then put them in a Device Group. The non-dimming single pole doesn’t handle any load - it is just there as a glorified wifi button to tell the other switch what to do. If you use a 2 button (non secondary MCU) switch as the non-dimmer, you can even fancy things with short press up, short press down, long press up and long press down. Either preset dim levels or hold to dim on the non-dimming switch.
Hi im reading this post… And want to apply an external antenna to see if I can improve reception/emission…
I saw the the “A - wifi antenna” its simple
My doubt is the “shield” where to solder
So I am looking to do the solderless flash. I have everything apart and the can off. It seems to me that the GPIO pin goes to a via just down and to the right so it should be possible to remove a little of the solder mask and get a wire on that rather than try to hit the pin with a needle. Does that sound reasonable? Is there a pull-up resistor on GPIO0 that might also be accessible?
Then again, it seems that there are some issues with these units. Would I be better off just to trash them?
Well, pulled an esp01 out of the box today, gave it a quick flash and attached it to the board and it works fine. It does need to have a resistor of some arbitrary value (I believe 10k is typical but I just grabbed what was nearest to hand) to pull up ch_pd. Other than that, because the Tuya only talks over serial, it’s basically no different. It’s currently hanging out kinda loose so I need to make it fit but if an esp12 can be made to work, an esp01 certainly can.
Glad that worked out for you. I did basically the same thing once on a Lohan Candelabra I started this method for, except it was the smd cap directly above yours… got super lucky and found it still sticking to board, and just soldered it back on.
I have followed @Technowizard (mostly) solderless approach on two Costco Feit dimmers but am having the same problem with both. First off, thank you @Technowizard for the simplified approach. This was very easy to do and all worked out well until the end. Here is my problem. I successfully flashed Tasmota (using current latest version, 12.3.1) and I am able to control the switch, dimmer and toggle, from the Tasmota UI. My problem is that the Tasmota UI does not properly reflect the state of the switch when I use the physical switch itself. For example, if the switch is on and I turn it off by clicking the switch, Tasmota UI does not reflect this state change. I also noticed that in the tasmota console, I never see a response from the heartbeat send. I have the exact same problem with both switches. I also confirmed that my solder for the txn line is back and it is not shorted to ground. Any ideas?
