Connecting to Arduino
Although designed for the Raspberry Pi, RPi900 can interface to anything using a 3.3 V serial signals. Serial JPEG cameras are one possibility; another is a microcontroller project of your own design, such as an Arduino project.
To connect with device, solder a connector of your own choosing on the top side of the board in place of the bottom-side sockets supplied for headers P1 and P5. Most 0.1”, 5-way connector styles should fit. A second, 2-way connector can optionally be fitted if you intend to use the hardware flow control signals. (If you are only sending small amounts of data at a time, this should not be necessary; the DNT900 buffer holds 1024 characters.) The locations and pinouts for the connectors are illustrated below.
The 5 V power supply can be powered down by the radio, allowing you to switch your serial device on and off remotely. Importantly, the TXD, RTS and SLEEP signals require 3.3 V logic levels. Using 5 V levels will damage your radio. Your Arduino or other device will ideally include its own 3.3 V regulator, powered from the 5 V supply.
A likely scenario is to have a Raspberry-Pi-connected RPi900 as a base station, with other devices connected to remote RPi900s. Using the DNT900 line discipline, the Raspberry Pi provides a separate, transparent TTY for communication with each remote device. The remote radios can be set to transparent mode, allowing them to exchange data with the base station without implementing protocol mode. Any configuration changes in remote radios can be made by the Raspberry Pi. The remote devices can also be powered down by the base station when not needed, reducing their power requirements and allowing for smaller batteries.