RPi900: Wireless Telemetry and Automation on the Cheap

RPi900 interface board

RPi900 is an interface board for the $25 Raspberry Pi single-board computer. Combined with a $70 DNT900 radio transceiver from Murata, it provides a cheap, powerful solution for any project requiring long-range, wireless data transmission.

Raspberry Pi

Tiny Linux computers are a hobbyist’s delight, and Raspberry Pi’s vibrant community and strong open-source software support have made it a runaway success. Its low cost, diminutive size and accessible low-level hardware make it an appealing target for all sorts of embedded computing projects. A $25 Linux computer? I’ll take two!

The Raspberry Pi provides numerous connectors including USB, ethernet and HDMI. A fantastic 5 MP camera is available for imaging and HD video applications. The operating system and software reside on an SD card. Several Linux distributions are available, with lots of online resources to help you get started.

While designed for the original Raspberry Pi models, RPi900 can be made to work with the Raspberry Pi 2 and Zero with just a small additional soldering modification during assembly.

Raspberry Pi model A

DNT900 Radio Module

The DNT900 is a 900 MHz, frequency-hopping spread-spectrum radio transceiver with maximum transmitting power of 1 W and a range of up to 40 miles. Data transmission rates of up to 500 kb/s are possible, depending on range. Point-to-point links between two radio are easy, as are more complex networks of multiple remotes. The radio also includes analog and digital I/O for sensor applications. It operates in the ISM band and is FCC certified for unlicensed operation. At $70, this radio is probably the most affordable in its class.

Also available is the fully-compatible DNT2400 module for operation in the 2.4 GHz ISM band.

DNT900P radio module

RPi900 Interface Board

RPi900 provides the ‘glue’ to combine these two devices into a ready-to-use package for remote telemetry and automation projects. A power source (battery, solar panel or DC adaptor), antenna and enclosure are the only extras needed to get up and running.

RPi900 can be used in several configurations. As a base station, it offers an easy way to talk with one or many remote stations. A driver takes care of the radio’s communication protocol: each remote radio presents its own virtual TTY device. It is even possible to provide a network connection to a remote Raspberry Pi using PPP.

As a remote, RPi900 enables numerous automation and telemetry applications. The low power requirements of the DNT900 and Raspberry Pi make them great for solar-powered applications; RPi900 can remotely power down the Raspberry Pi for further power savings. RPi900 can also connect with other devices (such as an Arduino or other embedded system) using a standard serial port, enabling extremely light-weight remote stations.