Use arduino nano for automatic open of an intercom(interphone) when dialing (digital one)

Starting from this post Use Arduino nano for automatic open of an intercom(interphone) when dialing I want to do the same for the digital version of the interphone.
I know that can be done because I saw one for selling but I want to extend it to ESP8266 + Home Asisstant.

I connect +14V to Arduino Vin, GND to GND, DATA to Arduino D4 and COM to Arduino D2. I am able to get the trigger by using this code:

int Call = 2;
int Answer = 4;

void setup() {
  pinMode(Call, INPUT);
  pinMode(Answer, OUTPUT);

void loop() {
  int calling = digitalRead(Call);
  if(calling == 1) {

But I'm not able to answer and to open the door.
I tried to set the digitalWrite(Answer,LOW); and digitalWrite(Answer,HIGH); but nothing changed.
If you have any idea it will be great.
Thank you!

Hello, Can you give me all the code too?

Hi, this is what l’m trying here... I don’t know how to do it and I need some help from the masters. :slightly_smiling_face:

Hello, did you managed to do it?


Hi, I managed to capture with an oscilloscope the signal the interior post is generating on DATA line when answer button is pressed and also when unlock button is pressed. I'm able to simulate those signals with an arduino but I'm still trying to figure out why this generated signals do not work as intended. I'll post the code if I figure it out. Meanwhile I can share those signals if there's interest.

What's weird is that the data line that enters the apartment (not the interior post data pin) is constantly outputing a 50Hz 90% duty cycle square wave while idle. When someone is calling that signal changes to a double square signal with a longer delay between each pair.

Also, when interior post is powered without the data line, there's no activity on the data pin and the buttons LEDs do not light up when pressed. If I wire the data line, button LEDs work but no signal is generated. Only when someone is calling those signal (answer/unlock) are sent on the same wire. So the weird thing for me is that the signal the interior post IC is generating is transmitted on the same line it's receiving. Did a google search and now I'm trying to understand 1 wire protocols.

Disclousure: I'm just an electronics hobbyist so any help would be well appreciated :slight_smile:

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