CAN bus for home automation

Here’s one node on the new home automation system on which [Black Rynius] is working. So far he’s testing out the system with just two nodes, but plans to build more as the project progresses. He’s chosen to use the CAN bus for communications; a protocol which is most commonly found in automotive applications.

The biggest plus about using the CAN bus is that it requires just one pair of wires for communications. As you can see, there’s an old doorbell included on this board and he’s hoping to use the existing doorbell wire to connect between nodes. Each unit includes a PIC 18F4580 which has a CAN engine built into it for easy protocol translation. There is also an MCP2551 which handles the transmissions. You can read a bit more about the hardware choices in his breadboarding post.

So far almost everything is working as planned. He’s able to send and receive data between the two boards including temperature from a sensor and time from a DS1305 RTC chip. The one thing that vexes him is that doorbell. It draws too much current for the wall wart that’s powering the board, browning out the microcontroller and causing a reset. That’s not a hard fix and we look forward to more developments in the near future.

[via Dangerous Prototypes]

HsNet: Node communications for feature-limited microcontrollers

[Diego Spinola] wrote in to tell us about a node communication system he’s been working on called HsNet. The aim is to build a system of nodes that can be made up of small and inexpensive microcontrollers. The problem is that the least expensive controllers often don’t have a hardware UART. HsNet implements the RS485 protocol using a software UART along with a slim and sleek addressing scheme.

The first module developed, seen in the image above and video after the break, is a single channel pulse-width-modulation node using a PIC 12F683. It can be sent commands in the payload of the HsNet packet format. The PWM modules accept three different commands; one is a desired PWM value, another is a delay between steps for the PWM, and the last toggles a blink function.

He has also developed an analog sensor module and an Arduino-based TCP/IC gateway module. Now that the packet communications have been established, it will be rather simple to add nodes based on that groundwork. [Diego] brought these components together to build an interactive wall which can also be seen after the break.

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