With the gpio pins being so vulnerable:-
An input will fail if you apply 3.3v without any limiting resistor - an output if set at 1 will fail if shorted to gnd - on output set at 0 will fail if you apply 3.3v without any limiting resistor
then I thought it worthwhile to set up safe insulated access to the pins as in attached pic. The pi is held in position with terminal blocks which are bolted to a piece of 4mm ply, and the connections are made to 3 @ 5A 12 way terminal blocks
(EBAY NO 150493789204)
which are clearly labelled to reduce
errors and are also bolted to the ply. The connection to the blocks is made with a 26 way socket FARNELL NO 381-5730 and a ribbon cable.
