Wiring information doesn't work with V3 of the Wemos D1 about mitsucon HOT 8 OPEN

I had the same problem when using a Wemos D1 mini clone from Amazon (B081PX9YFV). I took a look at the serial signal and noticed that the negative signal on the Rx pin was only getting down to 1.8V. I added a 1k ohm resistor between the Rx and ground pins on my level converter, and that solved the problem. I tested a few different pull-down resistor values, and anything from about 100 ohms - 1.5k ohms seems to work.

One benefit of this approach is that you can still program the device from the USB port if needed.

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Yes. That's correct. The scope readings were taken on the CN105 side.

So the "Tx line" scope readings were taken from the red wire (HV1) going to the CN105 connector, and the "Rx line" scope readings were taken from the black wire (HV2) going to the CN105 connector

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Thanks for information. I noticed this too but I can't figure out what happen so I just stick with V2 board. About softserial it need more work from upstream library SwiCago/HeatPump#136 .

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@danolson1 Thanks for this - I was having the same problem with a similar ESP board.

Can you clarify the pinouts? I'm looking at your pic and it isn't entirely clear but for what you're calling the "Rx" pin where the resistor goes did you mean it is for the Rx signal line on the ESP board side (which would actually be the Tx pin on the Heat pump CN105 connector side). That's what it looks like from the picture, unless I'm just confusing what I see.

So the pinout looks to be:
CN 105 Tx (Black wire) -> HV2 <> LV2 -> ESP Rx (aqua wire)
CN 105 Rx (red wire) -> HV1 <> LV1 -> ESP Tx (blue wire)
CN 105 5V (yellow wire) -> HV <> LV -> ESP 3.3v (white wire)
CN 105 GND (green wire) -> GND <> GND -> ESP GND (black wire)
1k resistor between HV2 (CN105 Tx) and GND on HV side of level converter
plus the CN105 5V connects to the ESP 5V

Is that correct or am I mixing up the Rx and Tx lines?

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Is there anyway to test this quickly w/o a scope? Supposedly - the board diagram claims to have the resistor needed, but the actual picture of what was sent was different. I want to make sure I'm going to be OK before I bother mounting into a HVAC unit.

I may have already missed the return window, but.. worth finding out before hand.

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A scope is pretty useful for this sort of thing. You could build your circuit on a breadboard at first. Then it's easy to test different pull down resistors.

I've tested w/ a multi meter.

By setting the pin 1 & 3 to pinmode function 3 in Arduino IDE, and then setting it as an output, I get 3.3v when high and 0 when low. (basically, the opposite of the LED)

No resistors, no extra board.

Will the D1 work correctly w/ the Split.. is the key question. I suspect the answer is yes, since it seems like it has the same behavior between both TX & RX, which would align better w/ the board V2 (resistor on both TX & RX) vs v3(which has only one resistor).

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I had the same problem when using a Wemos D1 mini clone from Amazon (B081PX9YFV). I took a look at the serial signal and noticed that the negative signal on the Rx pin was only getting down to 1.8V. I added a 1k ohm resistor between the Rx and ground pins on my level converter, and that solved the problem. I tested a few different pull-down resistor values, and anything from about 100 ohms - 1.5k ohms seems to work.

Thanks so much for this - the 1k ohm resistor worked great for me with this same clone board.

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