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Home and building automation carrier taps Raspberry Pi CM3

Dec 4, 2017 — by Eric Brown 3,557 views

Acme’s “CM3-Home” home automation carrier board for the RPi CM3 includes opto-isolated RS485, TP-Bus/KNX, and Light-Bus/DALI links, plus Grove support.

Italy-based Acme Systems, which has launched several Linux-friendly COMs like the Atmel SAMA5 Acqua A5 and RoadRunner, has turned to the Raspberry Pi Compute Module 3 Lite (CM3) as the foundation for its new CM3-Home home automation carrier board. Designed for OEM market and installation within a DIN-rail switchboard, the CM3-Home is available in a consumer-oriented, 130-Euro ($154) Lite model and a more advanced, 330-Euro ($392) “Full” version that targets commercial building automation.

CM3-Home (left) and CM3-Home architecture
(click images to enlarge)

The Full version supports connections such as a Light-Bus for DALI (Digital Addressable Lighting Interface) lighting devices, and a TP-Bus (Twisted-pair bus) — via a Siemens TP-UART-2 — for KNX compatible lighting and automation devices. The Full model also offers dual ADC lines via screw terminal, and provides standard features that are optional on the Lite model. These include 2.4GHz WiFi, an IR receiver, and an SPI/GPIO based LCD interface for an optional 2.2-inch, 320 x 256 resistive touchscreen.

CM3-Home “Full“ detail diagrams for TP-Bus (KNX) expansion at left and Light-Bus (DALI) at right
(click images to enlarge)

The Full version is additionally equipped with a Cortex-M0+ based, 22 x 14mm Microchip ATA8510 ISM transceiver module that supports Acme’s open source YARM RF radio module spec. The module operates at an 868MHz frequency, and is compatible with Acme’s ISM 868MHz Energy Harvesting radio nodes.

Otherwise, the Lite and Full models are identical. They are both designed to plug in an RPi CM3 Lite module (no eMMC) with a quad-core, Cortex-A53 Broadcom BCM2837 SoC clocked to 1.2GHz. In addition to the 1GB of LPDDR2 RAM on the module, the CM3-Home integrates a microSD slot with a card preloaded with a Linux distribution and drivers.


The CM3-Home includes a 10/100 Ethernet port, 2x USB 2.0 host ports, a stereo audio output, and a MIPI-CSI connector for a Raspberry Pi camera. There are 2x opto-isolated RS485 buses, which are “commonly used to connect DMX512, Modbus or generic RS485 serial devices,” says Acme. Like many of the other low-power interfaces, it’s available via a screw terminal plug connector that runs along one side of the board.

YarmDev board with Yarm (Microchip ATA8510) ISM transceiver (left) and optional ElBag DIN-rail enclosure
(click images to enlarge)

The board is further equipped with a 1-wire bus, 2x low-power relays, opto-isolated dry contact inputs, and 2x 3V3 TTL level serial ports: one for a system console and the other for an external microcontroller. There’s also a pair of I2C buses for Seeed’s Grove modules, as well as a wide-range 12-24V power input. Options include a 9-module MR9/K DIN-rail case from ElBag, as well as an optional USB-based WiFi module and antennas.

Although the CM3-Home is aimed primarily at OEMs and system integrators, it’s also available in pre-integrated “ready-to-use” models from netHome and Ohasis. The latter is a spinoff of TanzoLab, an Acme-related home automation project that is supporting the CM3Home with documentation for integrating the device with various IoT standards and devices. These include OpenHAB, KNX, and other automation devices.

The CM3-Home shares some attributes with another recent Italian DIN-rail device based on the RPi CM3: Dek Italia’s Telegea Smart Hub. Dek Italia’s device is billed more as an IoT gateway than an automation hub, and offers sensor, serial, I2C, and XBee, among other features.

Further information

The CM3-Home is available in a 130-Euro ($154) Lite model and a 330-Euro ($392) Full version in single units, with volume discounts available. As noted above, the device is also resold by Ohasis and netHome. More information may be found on the Acme Systems CM3-Home product page.

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