Top and bottom sides of RPi900

Features

Select an RPi900 feature to read more:

The radio module forms the heart of RPi900, and connects to a 40-pin socket on top of the board. RPi900 will not function without a radio attached.

The DNT900 comes with an array of inputs and outputs: six general-purpose digital I/Os, three analog inputs and two analog outputs. A connector lets you attach external circuitry directly to these I/O lines.

If your remote station only performs simple switching and measurement, these I/Os may suffice; RPi900 functions quite happily without a Raspberry Pi attached.

RPi900 is specifically designed for the Raspberry Pi. The GPIO headers and a mounting post hold it firmly in place. The Raspberry Pi's footprint encloses the board for a compact assembly. While designed for the original Raspberry Pi models A and B, the newer models B+, A+, 2 and Zero are supported with a small hardware modification.

Connection to the Pi is made using the UART serial port, and includes hardware flow control. Communicating with the radio is simple using the Raspberry Pi's ttyAMA0 serial device.

On the older Raspberry Pi models, GPIO headers P1 and P5 are both used. (Some simple soldering is required to attach this unpopulated header.) On more recent Raspberry Pi models, a different header socket and a pair of jumper wires must also be installed during assembly.

RPi900 also uses the I²C bus, and provides a connector to add further I²C devices to your Raspberry Pi.

If your project makes only infrequent radio transmissions, it can put the radio to sleep using a GPIO. Trim your power budget and battery size!

In remote installations, it may be desirable to power down the Raspberry Pi when not in use. RPi900 provides means to accomplish this.

A load switch connects the Raspberry Pi to the main power supply. An output on the DNT900 radio controls the switch, allowing remote operation of the Raspberry Pi power supply. Turn your Pi on and off at will!

Signal buffers are provided to prevent the radio driving Raspberry Pi inputs while unpowered.

A remotely situated Raspberry Pi might not have a network connection. Since it also lacks an on-board clock, time-keeping can present a problem.

RPi900 includes a real-time clock chip for just this situation. A driver is available, making the clock easy to use with Linux on your Raspberry Pi. (Arch Linux ARM is recommended.)

A tiny backup battery is included to maintain time during power outages.

RPi900 provides regulated 5 V power to both the Raspberry Pi and DNT900 radio. Output current is rated to 1.8 A, sufficient to power both devices at maximum transmit power.

Provide unregulated power using an off-the-shelf 12 V DC adaptor. For remote installations, a terminal block connector is also available for wiring to a 12 V solar regulator and/or battery.

In solar- and battery-powered applications, you'll want to keep an eye on the power supply.

RPi900 provides circuitry to safely measure the input supply voltage using the DNT900 analog-to-digital converter. A jumper connects this circuitry if needed. Measure the supply voltage by simply reading the analog value from the remote radio. Great for monitoring your battery levels.

A good antenna will help improve the operating range of your project. The DNT900 module provides an U.FL connector for the antenna. U.FL, also known as UMCC, is a tiny surface-mount connector with limited durability. It's intended to be used with a short cable, or pigtail, leading to a larger bulkhead connector mounted on the wall of an enclosure.

This may not be the most convenient arrangement while you're experimenting with your radio. RPi900 provides an adaptor for an SMA connector, allowing you to mount small rubber ducky–style antennas directly to the board. The SMA connector may also be used as a bulkhead connector, providing a means of mounting the entire circuit board directly to the wall of an enclosure.

What's a good gadget without some lights? RPi900 includes two LEDs for quick observation of radio status. An orange LED indicates carrier detect, so you know if the radio is connected to its base or remotes. A green LED flashes during transmission or reception of data. Pretty!