Pi Zero Modification
With a minor modification, RPi900 can be effectively used with a Raspberry Pi Zero. This setup is especially compact and low-power. The mature version of the Pi Zero now includes a camera connector, making it ideal for remote imaging. At a low cost of US$5 per board, I recommend permanently installing the Zero on the RPi900 board.
Instead of a GPIO socket, a right-angle male header is used to solder the Pi Zerodirectly to the RPi900 board. These are cheaply obtained on eBay and elsewhere. Cut the header down to size, and with a pair of pliers, remove extraneous pins as illustrated below:
Next, position and solder the right-angle male header to your RPi900 board in place of the normal 26-pin female header. (The new header extends past the original RPi900 socket, but the removed pins prevent any conflict with the board.)
Next, install the Pi Zero at right angles, and solder the pins as illustrated below. (If you wish to re-use your Pi Zero, a 2x20 socket may be soldered to the Pi Zero, but as the Pi Zero is so cheap this is probably not worthwhile.)
Finally, two jumper wires must be cut and soldered in place. Solder GPIO pin 11 (carrying the RTS0 signal):
On the other side of the board, connect GPIO pin 36 (the CTS0 signal) with a shorter jumper wire:
That’s it! Your assembled board should now look like so:
Install the DNT900 module, and the Raspberry Pi Zero is ready to be booted up and configured for use with the RPi900 board. Be sure to install the latest version of the rpirtscts utility package, which auto-detects the Raspberry Pi Zero and enables hardware flow control accordingly.