I'm working on a project to drive a stove which is sending TTL half-duplex messages. So I decided to plug an ESP8266 (D1 mini, but should work also with an NodeMCU)
In order to separate emission from reception to correctly read packages on Rx and send them from Tx, I built this electronic (see attached). But, the signal at the Rx pin stay at +3.3V
I did several trials with other schematic (or only by changing the voltage supply for the NAND HCF4001BE to +5V) and I saw (with an oscilloscope) that the signal goes down to 3.3V but never bellow.
So when signal have a voltage is coming for a "1" at +5V the pin is at +5V and the "0" is at +3.3V instead of 0V. And when signal have a voltage is coming for a "1" at +3.3V the pin is at +3.3V and the "0" is at +3.3V instead of 0V.
So I'm struggling to read "0" and "1" received from the stove.
Does anyone have a clue to solve this ?