50pcs 100uf 50V Radial Electrolytic Capacitor 8x12mm
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I ordered a bunch of those NRF24L01 modules too, I will try that as transport and see if I can get a functional gateway.

• no need to use an arduino mega any more, a simple atmega328 will have enough pins
• it has an interrupt pin that will switch on when value of any input changes, then you can just check the values of input and check which one has changed. This also solves the problem of debouncing, interrupt will only be triggered once before you read the value of inputs, so you just need to wait a bit before you read the values and you have no problem.
• low power, only 1uA/IC. If you switch from arduino mega to atmega328 you will probably save more power than what the PCA9555s will use

I have a very old gateway. I believe it's still on MySensors 1.5 - but nor sure. It's just an Arduino Uno, which is connected to through USB to a Raspberry PI running Domoticz. All nodes have a NRF24L01+ radio. For me that works perfect. I have no issues with the setup.

Also how do you connect your Arduino to your gateway? I posted another thread about my gateway not picking up anything over serial, but I guess it doesn't work over plain serial ports without an RS485 module, so I need to figure out a reliable way to connect a gateway.

Don't forget to use protective diodes (sorry forget the English names) in each reed sensor. Not doing it could damage your Arduino mega.

Personally I'd split the sensors over multiple nodes. Right now no sensor will work if there's a problem with the arduino or when it's not powered. Using multiples will only result in some not working when there's a problem with on of your Arduinos

{
    "0": {
        "sensor_id": 0,
        "children": {},
        "type": 18,
        "sketch_name": null,
        "sketch_version": null,
        "battery_level": 0,
        "protocol_version": "2.3.2",
        "heartbeat": 0
    }

  for (byte i = 0; i < 22; i++) { // access all 22 elements
    present(i, S_DOOR);
  }

The i is good for accessing the array. The only thing where you want something to change is where you access a pin:

void setup() {
  for (byte i = 0; i <22 i++) {
    debouncer[ i ] = Bounce();
    oldValue[ i  = -1;
    // Setup the button
    pinMode( i + 22, INPUT_PULLUP);// <---- here you want add 22 as the pin offset
    // After setting up the button, setup debouncer
    debouncer[ i ].attach( i + 22 ); // <---- here you want add 22 as the pin offset
    debouncer[ i ].interval(5);
  }
}

This way you don't go out of the bounds. And only for the pins you need to add the offset. For the rest off the code the way I propose makes it much more easy to read.

Hope it makes sense

#define MY_DEBUG
#define MY_GATEWAY_SERIAL
#define MY_BAUD_RATE 9600
#include <MySensors.h>
#include <Bounce2.h>

Bounce debouncer[48];
int oldValue[48];
MyMessage msg(0,V_TRIPPED);

void setup() {
  for (byte i = 22; i <= 54; i++) {
    uint8_t arrayIndex=i-22;
    debouncer[arrayIndex] = Bounce();
    oldValue[arrayIndex] = -1;
    // Setup the button
    pinMode(i, INPUT_PULLUP);
    // After setting up the button, setup debouncer
    debouncer[arrayIndex].attach(i);
    debouncer[arrayIndex].interval(5);
  }
}

void presentation() {
  for (byte i = 22; i <= 54; i++) {
    present(i, S_DOOR);
  }
}

void loop() {
  for (byte i = 22; i <= 54; i++) {
    uint8_t arrayIndex=i-22;
    debouncer[arrayIndex].update();
    // Get the update value
    int value = debouncer[arrayIndex].read();
    if (value != oldValue[arrayIndex]) {
      // Send in the new value
      send(msg.setSensor(i).set(value == HIGH ? 1 : 0));
      oldValue[arrayIndex] = value;
    }
  }
}

@TheoL I'm using an Arduino Mega, thank you so much for pointing out issues I'm likely to have. I've been trying to fix errors one line at a time, and I'm nowhere near a C expert. I'm good at copy/paste and hacking code together, but not so good at fixing harder to see issues such as those. My home has wired reed sensors, there's about 32 wired reed sensors, a few wired motion sensors which I haven't tried connecting yet, and audible alarm. I didn't want to subscribe to a monthly service, wanted to come up with a custom solution that can integrate with other smart solutions in my house. Originally this was going to be a programming project for me, but the scope increased, and now I want to integrate this with Home Assistant to have useful solutions instead of pet projects.

Wiring is extremely straightforward, I have 32 of the reed sensors. One wire from each sensor is connected to Arduino ground, and I used the double row of pins (22-54) to connect the other wire from the sensors. Arduino is connected to a Raspberry Pi through USB, which is the gateway, and I have Home Assistant running on an ESXi VM on my home server which will function as the controller. Once I get these running, I intend to add 2-3 fixed wired reed sensors to the same Arduino, and after those another 10-15 pir sensors through a wireless connection to the gateway, if I can figure out how to compile the gateway for both r485 and some flavor of rf.

Also curious how you get that many pins? Which board are you using?

Bounce debouncer[32];
int oldValue[32];
MyMessage msg[32];

void setup() {
  for (byte i = 22; i <= 54; i++) {
    debouncer[i] = Bounce();
    oldValue[i] = -1;
  }
  for (byte i = 22; i <= 54; i++) {
    pinMode(i, INPUT);
    digitalWrite(i, HIGH);
    debouncer[i].attach(i);
    debouncer[i].interval(5);
  }
}

You have a possible memory allocation problems with this part. The index of the first element in an array is always 0. You start at index 22 and end at 54. And the two for loops could be combined.

like so.

Bounce debouncer[32];
int oldValue[32];
MyMessage msg[32];

void setup() {
  for (byte i = 22; i <= 54; i++) { // I assume you start at 22 for an offset
    debouncer[i - 22 ] = Bounce();
    oldValue[ i - 22] = -1;

    pinMode( i, INPUT); // <------ pin 22? That one is not available on any uno, nano or micro
    digitalWrite( i, HIGH); // <--- I think you want to use INPUT_PULLUP in the pinMode
    debouncer[i - 22].attach(i);
    debouncer[i - 22].interval(5);
  }
}

All I did was fixing the wrong Array indexes. Maybe it's a good idea to post a wiring diagram of how you attach things. I might be able to help you more

I also think you want to use () instead of []

msg[i].setSensor[i];    // <--- you are trying to call an element of the array setSensor
msg[i].setType[V_TRIPPED]; // <--- same, calling an aray

These are functions and functions use ()

msg[i].setSensor( i );
msg[i].setType( V_TRIPPED ); 

send(msgPir.setSensor(Number).set(State?"1":"0"));

You can just create one message, then before you send it set the sensor attribute then set the value and send. No need to create 32 instances of the message object.