I still have the handouts Tom gave out for the board; here’s what it has to say (somewhat summarized):
For the VIN connector, + is VIN, centre pin is ground, and the far pin is 5V.
There are a number of solder jumpers on this board to provide for flexibility. The VIN-Enable and 5V-ENABLE jumpers are for advanced use. If in doubt, do not connect them.
Arduino:
Connect an external supply to VIN (eg 12V) and GND only, do not connect to 5V if 5V-ENABLE is set.
VIN-ENABLE: Enable power to the attached Arduino from the VIN connector + terminal (12V max).
5V-ENABLE: Enable 5V to FET board from Arduino for low current use.
Raspberry Pi:
Connect an external supply to VIN and optionally 5V if 5V-ENABLE is set.
VIN-ENABLE: Unused
5V-ENABLE: Enable 5V to Raspberry Pi from VIN connector, no protection. Use with care.
Underside Solder Jumpers:
There are 8 solder jumpers on the underside for advanced use. They are configured for outputs to create a 12 channel output only board. Reversing ALL the solder jumpers and omitting Q9-Q12 will allow JP9-JP12 to be used as opto isolated inputs. You will also need to join the pads for pins 2 and 4 in place of Q9-Q12.
These features are untested, use with care and read the schematic first.
Pin Mappings:
Connector / Arduino Pin / RPi GPIO
JP1 / 2 / GPIO7
JP2 / 3 / GPIO11
JP3 / 4 / GPIO8
JP4 / 5 / GPIO25
JP5 / 6 / GPIO9
JP6 / 7 / GPIO10
JP7 / 8 / GPIO24
JP8 / 9 / GPIO23
JP9 / 10 / GPIO22
JP10 / 11 / GPIO21 [27]
JP11 / 12 / GPIO18
JP12 / 13 / GPIO17
RPi rev 2 changes are shown in