On 22 March 2017 I went to the High Tech Campus in Eindhoven to attend a seminar about 'smarthomes' (presented by tweakers.net). I am renovating my bungalow from 1967 and was curious about the current state of technology for smarthomes. I decided to turn my home into a smarthome. It's already disconnected from the gas supply line and it will be a house with a heat pump and solar panels. So besides the water the house will be a 100% sustainable home.
Now I am looking for a smart solution for my smarthome. The Loxone Miniserver is a very nice device, but additional KNX devices that you need for the system are very expensive. Let's make a cheaper solution to expand the inputs & outputs. A device that can be connected to the network and send the active button signal to the Loxone by ethernet. I also can add a KNX connection and Modbus, but I need someone to write the firmware for this. This project can also be used by someone that doesn't use a Loxone. With a webpage on the ATSAMD21 you can have a realtime insight in the digital inputs and set the digital outputs. But the device can also generate TCP request when an input changes. You can also connect some PIR sensors on the digital inputs (with a AC to DC level adapter in between) and generate an alarm when you're from home (send a notification by the internet to your phone).
These are my first thoughts about the hardware:
* 16 digital inputs (electrically seperated by opto couplers)
* 16 digital outputs (can be connected to SSR, https://www.aliexpress.com/item/10DA-Din-rail-SSR-quintuplicate-five-5-input-3-32VDC-output-24-380VAC-single-phase-DC/1581576845.html)
Update. There will be 64 IO's on this board. These IO's are not protected (because it more difficult to protect an IO instead of just protecting an input or just protecting an output)
* controller is the ATSAMD21. This controller is arduino compatible (with the right firmware inside)
* The ATSAMD21 has no ethernet connection. That's right. That's why I will add an ENC28j60 device (SPI to ethernet). I will also add an ESP8266 device to communicate by WiFi
* Modbus interface chip. I will connect a MAX485/SP485/ST485 to the ATSAMD21
Update. 2 RS485 connections will be on the board. 1 for the Modbus and 1 for the DMX512 bus.
* KNX interface chip. The NCN5120 can be connected to the KNX bus. The software stack is the problem. Please help ;)
* Step down power converter. The 24VDC will be converted to 3v3 for powering the MCU.
I don't know if just one ethernet connection is sufficient, but I am also able to connect the other interface chips. I need someone to write the firmware for the controller. I don't know if it makes sense to implement all these bus standards, so I can also remove some interfaces from the project. Please leave me a comment about your thoughts. I want to be able to connect this device to the Loxone. This board will also support MQTT. I am still new in home automation, so I am updating the specs as we go on with the project.
Ps. the picture is of an existing modbus board that has 16 inputs and 14 output relays