When using an Input module, all switches needs to be connected in STAR towards the Input module. To allow customers to also use BUS connected switches, we've developed hardware and firmware to make this possible. For these BUS connected switches, we've decided to use the CAN protocol since this protocol is designed for environments with high distortion which makes this a very reliable solution.
We've 2 types of hardware designs that we've made:
- CAN Control: This is the CAN gateway that will convert RS485 message to CAN messages. When using CAN switches, 1 CAN controller is needed.
- CAN Switch: This is the hardware that will contain up to 8 switches, temperature sensor, humidity sensor and up to 8 leds. It will have 2 PCB designs:
- CAN Switch for Niko: Niko switches have a small PCB behind their switches. To make an Openmotics CAN switch, just change the Niko PCB by an Openmotics PCB.
- General CAN Switch: This small PCB will contains all the connections to connect any kind of switch.
How does it work
The CAN control unit is connected to the RS485 bus and to the CAN bus and will convert the messages between CAN and RS485. The CAN control unit is the start of the CAN bus. The CAN switches will be connected in BUS starting at the CAN Control unit and going from 1 switch to the other.