RoadTest: PiRack Accessory board for Raspberry Pi
Evaluation Type: Independent Products
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: N/A
What were the biggest problems encountered?: Does not fit off the shelf IDC connectors Lack of documentation for jumper usage
I have been offered the opportunity to review an interesting piece of hardware for the Raspberry Pi single board computer.
The item is the PiRack designed by PiFace.
Visually the PCB is a dull green, matt and plain looking. There is very little documentation about the board. One of the aims of this review is to provide some useful information about the board.
The purpose of the board is to allow multiple addons to be used simultaneously, thus expanding the potential of the Raspberry Pi.
As it is designed the board can host 4 other addons. If you were to use multiple PiRack boards this could be expanded to a potential 7 boards.
The board is designed to be fitted to the GPIO pins of the Raspberry Pi in a vertical orientation which means that it will not fit standard cases.
One of the useful features of this board is that it allows the addons to be powered from a DC adapter rather than from the Raspberry Pi itself, thus neatly circumventing power draw issues. If you were to get a nice 5 volt 2 or 3 amp adapter you could run several boards easily.
As you can see the board has a large number of jumpers, 3 for each set of pins for a total of 12.
If we take the bottom row we have jumpers JP1, JP2 and JP9.
JP1 and JP2 are used to change the SPI pins 24 and 26 for an addon board.
JP9 is used to select the power source for the addon board, either 1-2 for the Raspberry Pi or 2-3 for the external DC socket.
Changes I would make to this board:
The first thing I noticed was that the board would not fit in standard cases. I would suggest extending the bottom of the board before the first set of pins by maybe 5 or so millimetres which would allow the board to fit in a standard case.
The second thing I would change is to offer a range of colours and finishes for the board. As it stands it looks rather cheap and could pass for something homemade.
The third change would have to be the available documentation for the board – it is non-existent. There is a web address on the board http://piface.openlx.org.uk which gives information about one of the other boards by the same manufacturer but nothing about this board.
There is plenty of free space on the back of the board for ready information about the jumper positions.
The fourth change would be to add a bi-color LED to each set of pins to show whether the board is receiving external power or power from the Raspberry Pi – or if it is powered at all.
The fifth change I would make is to trim the pins down on the back of the board, they stick out by almost 4 millimetres and really should be trimmed down at the production stage.
Any board that comes with switches or displays must be mounted above the other boards or they will become inaccessible. Whether this is an issue comes down to your personal plans for the PiRack.
For uses such as the PiFace this board is perfect – it will allow you to extend the number of inputs and outputs greatly.
Default jumper settings:
JP1, JP3, JP5, JP7: 1-2
JP2, JP4, JP6, JP8: 2-3
JP9, JP10, JP11, JP12: 2-3 (external)
When you change one of the jumper pairs JP1 and JP2, JP3 and JP4, JP5 and JP6, JP7 and JP8 ensure that the jumpers are not on the same pins (1-2 and 1-2). They must be either 1-2, 2-3 or 2-3, 1-2.
The power supply is 5 volts DC, centre positive. Ensure that you have a decent power supply of at least an amp, preferably more if you intend to use multiple boards.
The board is ideally suited to allow multiple one wire devices on the same pin.
This is hard to call. Would I recommend the board to a friend? Definitely. Do I think that it looks and feels like it was made at home? Unfortunately I say yes.
Give the board time to go through a few more design iterations and it will be a nifty piece of kit. At the moment it is just a little too unrefined for my liking. The best thing I can say is that it does what it is supposed to. How sturdy it would be with 2 of these end on end and with seven boards fitted to it I wouldn’t like to say.
I have grave reservations about shorts between adjacent boards and feel that this must be a major consideration whenever boards are mounted. Perhaps some enterprising individual could come up with clip-on plates that fit between each board. I know it could be done with something like a piece of cardboard but that is not practical in the long term.
The crunch question for me is whether I would consider using it on my extremely limited edition blue Raspberry Pi.
The answer I would give is “at this moment in time, no”. I would happily reconsider in a few iterations of the board when I feel that it looks as good as it could. Until that time, my blue Raspberry Pi will stay safely in its box.
I played with the PiRack for some time and bought some readily available Pi addons from a high street retailer to get a feel for the board.
Today I was using my Raspberry Pi and needed to use one of my addon boards, namely the “GPIO Board with Terminal Block For Raspberry Pi”, Maplin part number N31NT, http://www.maplin.co.uk/gpio-board-with-terminal-block-for-raspberry-pi-682474.
I realised that this was an ideal opportunity to test the board with the PiRack that I have been asked to review.
The GPIO board is a very useful piece of kit for tinkerers such as myself that regularly work on breadboards as the pins are all exposed, neatly labelled and easily accessible. Being able to secure the jumper wires onto the board is a godsend, it is very quick and reliable.
The GPIO board connects to the Raspberry Pi with a standard 26 way IDC connector, similar in style to an IDE cable.
Connecting it to the Raspberry Pi is straightforward, line the connector up and push onto the pins.
Doing the same on the PiRack has revealed a glaring flaw.
The jumpers on the PiRack phyically prevent the IDC cable from being connected – they are in the way.
As many people will get parts such as the GPIO board from the high street and similar outlets the likelihood of this being a showstopper is very high.
My solution would be to move the jumpers JP2, JP4, JP6, JP8 directly above the jumper they are currently next to and move jumpers JP9, JP10, JP11, JP12 to the left by approximately 5 millimetres which would give clearance for standard IDC cables.
I consider this a major oversight on the part of the PiFace team, and I hope it is rectified in the next board revision.