It uses a Terasic DE4 FPGA board with an Altera Stratix IV FPGA. It has a full set of peripherals on the DE4, as well as a battery, touchscreen and HDMI output - you can give presentations from your own FPGA design! As well as designing the tablet we designed the CPU and most of the peripherals that go on the FPGA.
This is the mechanical design - what you put on the FPGA is up to you! We hope to open source more of the components we use in our FPGA designs in future.
To build the Tablet you will need:
A DE4 FPGA board http://de4.terasic.com.tw
Terasic Multi-touch LCD module http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=68&No=653
HDMI Transmitter Daughter Card (optional) http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=66&No=582
Energizer XP8000 battery http://www.energizerpowerpacks.com/uk/products/xp8000/ (optional, ours came from CPC)
PicoPSU-80 voltage converter http://www.mini-itx.com/store/psu
Use of a laser cutter and some 1, 2, 3 and 4mm acrylic for laser cutting pieces
A collection of M3 screws and pillars - see the full parts list in github
There are two versions - one with battery and HDMI output and the other
without. These instructions assume you're building the battery version -
the non-battery version is simpler and you can just omit steps relating to
the HDMI and battery.
These instructions and design files are freely modifiable under the 2-clause BSD licence.
Computer Architecture Group, University of Cambridge Computer Laboratory
git clone https://github.com/ucam-comparch/de4tablet.git
or browse to https://github.com/ucam-comparch/de4tablet
You'll find some files beginning 1mm, 2mm, 3mm, 4mm - these are the designs
you need to laser cut. We used several types of acrylic:
1mm clear (for the battery cover)
2mm clear (for the PCIe protector)
3mm blue (for the baseplate)
4mm clear (for top plate, bezel and supports)
If you don't have as many types of plastic lying around you can vary the
thicknesses and colours - you might have to adjust some of the support
pillar lengths to fit.
Attach 5x 5mm M3 M-F pillars using M3x6 screws, to match up with the inner
holes on the DE4
4x 12mm M3 M-F pillars on the other side.
attached with the original 6x M3 pillars. Place this underneath the
nylon screws. Nylon screws are used here to avoid shorting out on the DE4
if the plastic flexes
than this (it picks up interference from the display), and you don't need to
use an 80 way IDE cable as the screen is supplied with. Make slits between
conductors to make the ribbon more flexible.
Now is a good time to fit SODIMMs to your DE4 (if you are using them) or setting any DIP switches as necessary.
G and G2 30mm (x5)
All the pillars are labelled in the stackup diagram.
If you can't buy these pillars, you can buy the nearest size and add
unthreaded spacers to extend them. The exact pillar length may depend on
the tolerances of your acrylic (which can vary widely) so you may need to
adjust them slightly.
Make sure the base plate is earthed so it holds no static charge, then screw
the base to the HDMI board with 2x 8mm M3 screws and M3 nuts
ethernet ports. You may need to adjust the pillar height supporting it -
the idea is that it's very close but not touching the pillars, so that the
connector is bearing most of the weight. Slip in a 1 or 2mm spacer in here
if necessary to support it.
of pillars B and C to fit. Ideally it should be spaced so that the bolt
heads on the underside of the HDMI board almost but not quite touch the top
of the ethernet sockets.
mounting plate and thread the power input cable through the larger of the
square holes. Cable tie the PicoPSU in place - the lock on the tie must be
on the opposite side of the mounting plate from the PSU.
adjustment of the pins to make it fit (the PicoPSU connector tends to curve
a little). Cut off the end of the cable tie.
with 5x M3 30mm screws and nuts and washers on the reverse. Also use 3x M3
8mm screws with nuts and washers on the lower three holes.
support, and screw on with nyloc screws (careful not to tighten too much).
There are dimples on the bottom of the battery which align with holes in
the battery support.
nuts (again, don't overtighten). It doesn't sit parallel to the lid, so
don't worry if it isn't flat.
power plug and a switch interrupting the positive rail.
a middle piece and a top piece that hold the switch in place - you may find
that another pair of side pieces is more convenient than the top piece.
The square top piece holds everything together, and are screwed on with 4x
M3 20mm screws and nuts.
don't snag on the fan.
supported correctly. As this depends on the tolerance of the acrylic, you
may have to adjust it slightly. Here's what I used:
A: 1mm + 2mm + 7mm
J: 1mm + 7mm
C: 2mm + 8mm
B: 2mm + 8mm (this requires thin-walled spacers - omit if you don't have
Screw these stacks together with M3 25mm screws.
Tighten all the lid screws and make sure it sits flat.
Now all you have to do is design what to put on the FPGA...