Copyright © Astro Designs Ltd. Registered office, Marlborough, Wilts. England

Mail: Designs Website (


With the exciting release of the Raspberry Pi Compute Module, we put our heads together and started doing some thinking. We’re looking at a ‘main board’ or ‘mother board’ designed to carry the Compute Module which we’re thinking of calling the ‘Pi Plate’… Although there’s another product on the market that has that name which is a shame so we might have to work on the name…

Some of our current thoughts…

Basic features of a simple carrier board: (= minimum cost)

1) Raspberry Pi Compute module connector;

2) Power supply connector (USB) providing a 500mA 5V supply;

3) 2-port USB hub and / or;

4) Ethernet connector plus 2 x USB connectors;

5) HDMI connector;

6) Raspberry Pi Model A/B compatible GPIO connector (could possibly be left off the board and fitted by the user if required to keep the cost down);

7) Remaining I/O to be made available on a second connector of some kind…

8) Optional connectors for CSI & DSI camera & display ports

8) Possibly a proto-typing area where the user could add their own additions?

Some extra features: (= higher but still reasonable cost)

1) Switch-mode power supply, capable of supplying 5V at up to (say) 3A to the module, carrier board and anything plugged in to it, which can run from a (say) 6-15V external unregulated power supply;

2) Slow (100ksps) analogue I/O, based around (say) an 8 channel 12-bit ADC

3) ArduinoTM compatible shield interface;

4) Optional Phono connector for TVDAC video out;

5) Optional 3.5mm stereo jack socket for audio out

6) Audio in?

More advanced features (equals quite a bit more cost)

1) Mass-memory module (volatile), possibly DDR, DDR2 at best (chosen for cost rather than bandwidth) accessed over USB;

2) Probably using an FPGA to implement #1 - which could possibly be re-configured by the user for their own custom application;

2) Capable of supporting up to four R’Pi Computer modules,

a) Each module has its own USB & Ethernet connector;

b) The second USB port from each module (via it’s LAN9512 ethernet adapter) is connected to a central memory array that is shared by all modules, providing a reasonably high bandwidth inter-module communication mechanism;

c) Each module has a separate SPI channel available on a GPIO connector;

d) A second SPI channel on each module connects to the FPGA. This provides a secondary medium-bandwidth inter-module communications link;

e) The RXD/TXD serial interface from each module connects to a ‘port switch’ within the FPGA, providing a low-bandwidth communication channel between each module;

4) Option for a USB to SATA interface, providing capability to add (say) a 2.5” disc drive;

5) Option for two fast (> 1Msps) analogue inputs;

6) RS232 / RS422 serial interface - old technology I know but sometimes basic is good… This could be user-mapped to any Raspberry Pi Compute module installed using the ‘port switch’ described in 2e;

Possibly a little whacky…

1) PCI Express (single-lane) compatible carrier board (another one for an FPGA…) allowing the R’Pi to be joined to (say) a desktop PC. Can’t think of an application yet but maybe someone else can?

2) Some or all of the features found on the PiXi board?

Watch this space for more of our thoughts… and some diagrams would probably help too…

If you have any thoughts on what you’d like to see on the Pi-Plate or whatever we end up calling it, why not drop us an email at