I was fortunate to get my hands on an early release of the PiFace PiRack. (I prefer to use the small i in the blog)
This has been mentioned in the PiFace documentation, but there was little other information.
The PiRack is designed to extend the GPIO pins of the RPi (Raspberry Pi) out to a series of right angle headers, and an end connector.
You then stack 4 x PiFace Digital boards (or any other boards) onto the connectors.
A second PiRack fitted to the last connector gives the option of seven boards.
As the video explains, 7 boards gives 56 Inputs and 56 Outputs.
To overcome the supply issues, the designer ( Dr Andrew Robinson )has fitted a DC jack to provide external power.
He also fitted jumpers to select the 5v source (external or from Pi) and allow the select lines to be jumpered to avoid two boards having the same address.
Photo from above the basic unit. Right side plugs into the Pi, while the left end is available for connections or another PiRack.
Photo of two PiFace Digitals fitted showing the clearance from the Pi, which allows the camera and other cables to be fitted.
End view showing Input cabling distance from baseline. Consideration when mounting should factor in cabling.
Two official photos showing the RPi with camera and PiFace Digital attached using the PiRack
There are 4 mounting holes provided to secure the unit, however clearance for the Input cabling should be considered, as the photo above shows.
I'm not sure about permanently mounting the RPi or the PiFace Digital without some additional support that holds the boards at the correct spacing.
It is not good practice to use the connector as a sole means of support, as any flexing/movement is transferred back and results in the solder joint cracking.
The NZ pricing is $14.95 (plus GST = NZ$17.20) which is very good compared to the other solutions.
The official release note is here Press release
Safety and Jumper info is here Safety leaflet
The RPi comes with a GPIO that allows many other items to be connected, and unfortunately the PiFace Digital removed that while only using a few itself.
If you wanted to connect a temperature sensor that controlled one or more outputs, then you were out of luck, unless you fit two rows of connectors (see PiFace Digital )
Some items require power as well as the data pins (ie I2C LCD), so multiple devices can require some creative wiring in order to satisfy the hardware needs.
If you are still in the test or prototype phase this can be a hinderance or worse an accident that renders one or more parts to the scrap heap.
Using the PiRack gives 5 sets of the GPIO pins, and the option to power with an external 5v supply.
This would suit anyone contemplating servo control, as these generally cause issues with spikes on the 5v line.
As these come into use, I'm sure we will see some more creative uses that may or may not have been considered when first designed.
In the meantime, get your orders in as I suspect these will fly off the shelf, while I write a review for "The Shed" magazine