Analogue Input for Lego RCX Module

Up to now, there has not been an analogue input for the RCX block. The circuit presented here allows the RCX block to detect analogue voltages. The approach used here even allows this function to be used with existing Lego software, although this naturally amounts to a certain ‘misuse’ of the interface. If an RCX input is set to the ‘light sensor’ mode, the internal logic senses the resistance between the two terminals of the selected input.