@foad62
Sorry for late reply... If you use MQTT Gateway you need an MQTT broker. I was using mosquitto as a broker. At HA site they mention it at MQTT component page: https://home-assistant.io/components/mqtt/ but now they also have one internal broker available, so they are many available possibilities.

I did not work too much with github and still find it somehow a little bit annoying for me, but I was trying to do this.
I also have updated the new inserted constant as you advice.

The new definition should be moved to the MyConfig.h , but now it was easier to modify only one file.

My tests were done on MQTT Gateway made by Arduino Uno (clone) + Ethernet shield 5100 and it works very nice.

I succeed to add the retained flag for the MQTT Gateway.
To access this flag, I have inserted few modification into the file MyGatewayTransportMQTTClient.cpp
The whole code and instructions for use are here: https://github.com/Mihai258/MySensors_MQTT_retained/tree/master

@eyesoft
As far as I understand, MySensors relay on PubSubClient for MQTT and it does not allow to publish messages with QOS=1 or 2, only 0.
Retain is different that QOS, it offers the possibility to recover the state for a device that loose connection for a while (e.g. after a restart). I find it very usefull. For example I have to restart the controller. When come back I got all states to their real values if retain=true. Otherwise they goes to the default, usually 0.
I have now 6 nodes, each with several sensors and relays.

@eyesoft
Thank you for the answer, I am happy to get a confirmation about sensors works on a Pi Gateway. Since at least one of my sensor is analogue, I still have to add an Arduino board to the gateway, I plan to connect it via USB.
I have tested and get very good results with Home Assistant controller running on a Pi where I add sensors directly on Pi and to an Arduino (USB to Pi).
The Ethernet Gateway do not use IRQ: https://www.mysensors.org/build/ethernet_gateway
Nor the nodes: https://www.mysensors.org/build/connect_radio Even if the wire is connected at Arduino pin 2, is mentioned: Note: The IRQ is currently not used by the MySensors library so it can be left un-connected
If you know how to connect and manage this IRQ on Arduino sketch, please let me know.
I have built this some time ago and works without the IRQ connected. Now I have updated the MySensors to 2.1.0 , IRQ is still unconnected and works the same. As far as I see, it is used for the Pi Gateway. I plan to migrate to this configuration of Pi Gateway, but I would like to get more info before change my working system:

• this IRQ improve the reliability? (sometimes I have encountered problems due the load of NRF24 network with many messages)
• I would like to set retain=true for the MQTT Gateway, this will improve the reliability.
  I already addressed the last question somwhere else, still waiting for more info if somebody know.
  Thank you

I used two capacitors in parallel with big capacities, just to be sure here is no problem with power: electrolytic of 100uF + ceramic 470nF, presented here: https://www.openhardware.io/view/55 in the third picture.
For a smaller module, I think you can add a ceramic of 100nF to filter higher frequencies and a tantal or even electrolytic of 10uF, if you choose lowest voltage for them they should be smaller.

@dbemowsk
If it is used as an alarm system, not only for intruders, but for smoke detection, water leak etc you must count on its reliability close to 100%.
Also as mfalkvidd mention, you may not want to stay outside automated closed door...

The Pi MQTT Gateway with IRQ connected may handle better the messages into a loaded network than Ethernet MQTT Gateway where IRQ is not used? (with NRF24)
Also I would like to know if I can use the other pins of RPi to connect some digital sensors directly there.

@hek
Please let me know if in v.2.1.0 the ACK is enabled by default for NRF24 or if we may enable/disable it (where?).
Also I am interesting about the retain flag management from the gateway toward the mqtt broker: is it possible to manage it? How?
Thank you

I use this IR transmitter toward my LG Tv and it works at a distance of ~3.5 m, but IR LED must be well pointed to the Tv, otherwise it doesn't work.

They specify in Description section: Output Current: 12A, so this is maximum, still ok if you need 10A

It would be very nice to be able to choose between HA interface update/don't update for the same value. For me, I am looking for last time value change/receive also as a confirmation of node running in good shape. Thank you.

@DirkB19 It may take some time to follow the debounce procedure for each of the 16 inputs. For me, I have no big problems with delay, the commands act almost instantly. I do not use debounce, since no physical input there, while my node use 4 relays, several sensors, IR receiver (this take some time, but no big delay).

@parachutesj Inserting just Delay() into the code doesn't help always, while it may insert some other troubles, but trying to send messages with some other line code between next sending help a little bit.
My error messages was revealed after a lot of testing and stress of the nodes.
I am waiting for the MySensors library improving, I saw a lot of work there, so I will keep the actual config, minimize the testing nights for now. Of course I am hard resetting nodes from time to time, when they fail to respond. The gateway seems to works fine.

@DirkB19 , I just compile again this file and it works fine for me using Arduino IDE 1.6.5 on Linux, MySensors 2.0.0 beta, set Arduino/Genuino Mega or Mega 2560:

Sketch uses 40,046 bytes (15%) of program storage space. Maximum is 253,952 bytes.
Global variables use 1,404 bytes (17%) of dynamic memory, leaving 6,788 bytes for local variables. Maximum is 8,192 bytes.

I saw this library is continuously changed, while still beta and still the same version number from long tome ago! You may remove some important definition or included libs, or the actual MySensor development version need something different into the code. I may ZIP and send to you my working version of MySensors, but should this be the right approach?

configuration.yaml file updated on GitHub https://github.com/Mihai258/MySensors-HomeAssistant-Live

In HomeAssistant, if you use MQTT switch for example, with state and command topic, the command is send to the gateway when requested from the interface, but the switch on the interface change itself when it receive back the status from the gateway. If the message doesn't reach the destination and comes back with the new status, the interface doesn't change the switch state.
I encounter this situation a lot of times. After many tests, my findings show that the messages are lost between the nodes and the gateway, but I never miss a message between the gateway and the controller.
So, while it will be nice and useful to have an end-to-end implementation with ACK and automatically retries, the real problem can be solved if such mechanism will be available between nodes and gateway.

Thank you for my project appreciation.

My project is in running phase, I posted detailed description of functions, code and pictures on Openhardware site here: https://www.openhardware.io/view/55.