Have you ever wondered what you can do with your unused twisted-pair telephone wire running throughout your house? Well, how about using it as the transport medium for a CAN bus network of environmental sensors? This project, which I dubbed PhoneCAN, is a relatively easy project which uses Adafruit hardware and CiruitPython.  My setup uses four CAN nodes:

• A "home" node with an OLED Featherwing display on an RP2040 CAN feather with MCP2515 CAN controller that can show current values for all four nodes using the buttons on the display
• A "send" node with ESP32-S3 Feather and CAN bus Featherwing MCP2515.  This node gathers measurements from all nodes at a user-specified interval (I use 15 minutes), averages them over the interval, and pushes them to Adafruit IO.
• Two "remote" nodes which use RP2040 CAN Feathers with MCP2515 CAN controllers.
• I used two types of sensors (just because these were the ones I had on-hand) as I was interested in tracking temperature and relative humidity around my house.  Any of Adafruit's environmental sensors should work:
  • Sensirion SHT41 Sensor
  • MS8607 PHT Sensor
• Gather all those old phone patch cables that you have lying around in drawers around your house (be careful though, some cables have "swapped" wiring).  For most of my nodes I used RJ11 breakout boards to connect the three-wire CAN controller to my home phone jacks.

I have all of my nodes reading and posting measurements every second to the CAN bus.  Documentation and sample code provided on my PhoneCAN github repository.  I believe that this is a relatively easy project and was really a lot of fun to put together.  Best part?..  Using that old (abandoned by the steady march of technological progress) twisted pair phone cable sitting in the walls of my house.