It is important to use a cable that has a similar diameter to the one supplied with the joypad. A 15-core signal cable with an overall diameter smaller than 6mm should retain sufficient flexibility. A screened cable is not necessary, but it would provide an additional connection if required. Minimizing the connections The smallest number of connections is achieved by choosing a square block of keys within the matrix. The problem with this arrangement is that it maximizes cross-interference and for this reason many key combinations would not work simultaneously.
Maximum isolation is achieved by selecting keys with a unique input and output.
Unfortunately this would only allow eight buttons to be connected and we need 14 which would also require a total of 28 connection wires. Independent operation is also achieved by choosing keys that lie along a single input or output line. As already stated however, we would like to select from only the principle alphabet keys and the chance that 14 of these keys all lie along the same output line is extremely unlikely. However the key at the intersection of the two lines must be ignored as this would create cross-interference with all the other keys. This configuration would require just 16 connection wires for our 14 functions.