Switching matrix for an input device

A process for the detection of switching states of one, two or more synchronously actuated switching elements of an input device, using a group electrically connected to a microcontroller, with a plurality of N input and output lines with a serially connected terminating resistor to ground each, and a group with a plurality of K switching lines with a switching element and a series resistor each, whereby each switching line connects two of the N I/O-lines to each other, the process comprising the following process steps:

• providing a bit for each of the N switching elements and setting the key status bit to 0 for each of the N switching elements;
• setting all output registers to 0;
• setting all direction registers to output;
• passing through an external loop, whereby the number of loop passes corresponds to the number of N I/O-lines;
• passing through an internal loop, whereby the number of loop passes corresponds to the number of N switching elements and two interrogation patterns per switching elements are interrogated in each case;
• evaluating the input signals and detection of the switching signals by an OR relation of the key status bit to the new input signal;
• and
• checking whether there is a permissible key combination.