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Hackable Raspberry Pi add-on boards enable CAN-bus home automation

Jun 20, 2018 — by Eric Brown — 2201 views

Omzlo’s open spec “NoCAN” IoT platform for home IoT includes an “Omzlo PiMaster HAT” board for the Raspberry Pi that connects with multiple Arduino compatible CANZERO nodes on a CAN-bus cable that can stretch up to 300 meters.

Athens, Greece based startup Omzlo has won Kickstarter funding for a NoCAN platform for “wired IoT” home automation that connects sensor nodes to a Raspberry Pi. An Omzlo PiMaster HAT board mediates between the Pi and multiple, Arduino-compatible CANZERO boards that can connect sensors, lights, relays, and actuators for home and garden automation. The boards are connected via an Ethernet cable running the serial CAN-bus (or CANBus) protocol, which is commonly used in industrial and automotive applications.

NoCAN diagram
(click image to enlarge)

NoCAN is named for its Raspbian based “nocand” network manager app, which runs on the Raspberry Pi. As a bonus, Omzlo will be able to call the second-gen version of NoCAN the NoCAN Deux.

You can invest in Kickstarter packages through July 18 with shipments due in September. The 57 Euro ($66) Standard kit gives you an Omzlo PiMaster HAT board with spacers and screws for connecting it to a Raspberry Pi, as well as 2x CANZERO node boards. The kit also includes 5x screw terminal plugs for connecting the CANZERO boards to the CAN-bus, as well as a 120-ohm termination resistor. A 109 Euro Extended kit gives you 5x CANZERO boards and 11x terminal plugs.

With either kit, customers bring their own Raspberry Pi (any 40-pin model), as well as a 9V to 24V power supply for both the HAT and the Pi and some Ethernet cable. The NoCAN CAN-bus runs at 125Kbps, which is enough for a serial network stretching over 300 meters. Omzlo’s HAT and CANZERO boards are open source in hardware and software, and the company will provide schematics.

Omzlo PiMaster HAT with (left) and without Raspberry Pi
(click images to enlarge)

The Omzlo PiMaster is HAT board is built around a 32bit STM32F042 Cortex-M0 MCU running at 48MHz. The board talks to the Raspberry Pi via SPI and GPIO interfaces. It runs on 6V to 28VDC power and has a smart power switch with overcurrent protection.

Each of the 61.5 x 25mm CANZERO node boards is identical, and complies with the Arduino MKR form factor. It has the same 48MHz, Cortex-M0+ based Microchip SAMD21 MCU used by the MKR boards, and the pinout is similar to the original Arduino MKRZero, so it supports most Arduino MKR shields.

CANZERO, front and back
(click images to enlarge)

Omzlo supplies a CANZERO definition and libraries for the Arduino environment. Users can install them, write sketches in the Arduino IDE, and export them as compiled binaries. NoCAN software can be used to upload the sketches to any node.

Each CANZERO board has 256KB flash and 32KB RAM. The boards provide 22x DIO, 7x analog outputs, and a single analog input. There are also UART, SPI, I2C, and of course, CAN interfaces.

The CANZERO provides 3.3V (300 mA max), 5V (500mA max), and VIN supply (typically 12V) pins. Like the MKR boards, however, it’s designed to operate with 3.3V logic, and should not be connected to 5V logic without adding voltage shifting circuitry. The CANZERO nodes also feature “an efficient switching regulator to step-down the network voltage (e.g. 12V) down to 5V, and then a more traditional LDO to reach 3.3V,” says Omzlo.

CANZERO in an enclosure with BME280 temperature, humidity and pressure sensor (left) and CANZERO pinout
(click images to enlarge)

The CANZERO nodes communicate with each other and the HAT board using a publish/subscribe mechanism similar to MQTT. Each node can create a channel with a name such as “temperature,” and all the CANZERO nodes that subscribe to it will receive data published on it.

The NoCAN software, which can be run on the Raspberry Pi or any connected Windows 10, Linux, or Mac OS X computer, allows you to update the firmware of any CANZERO node over the network at any time. You can optionally connect the NoCAN network over via the Pi to the Blynk platform, which lets you control the network via a mobile app. This would let you, for example, use your smartphone to monitor your home’s temperature, receive notifications if a PIR sensor detected motion, or check if the lights were left on at home and remotely switch them off.

Further information

NoCAN packages are available on Kickstarter through July 18 starting at 57 Euros ($66), with shipments due in September. More information may be found on the NoCAN Kickstarter page and Omzlo website.

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One response to “Hackable Raspberry Pi add-on boards enable CAN-bus home automation”

  1. Max says:

    Welcome to the brave new world of 2018, where you need a second 32-bit ARM processor just to get the first one to communicate over CAN – a task others seem to manage just fine with a single slow 8-bit MCU. Granted, they aren’t running Arduino code…

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