Direct sensor interface (DSI) module

A direct sensor interface (DSI) module which allows a microcontroller to directly interface to sensors having at least one of a resistive, capacitive, and current source characteristics comprising, in combination:

• a sensor device which has a sensor current proportional to an output reading of said sensor device;
• a current mirroring circuit coupled to said sensor device for outputting a charging current proportional to said sensor current of said sensor device;
• a capacitive device coupled to said current mirroring circuit, said capacitive device generating a voltage as said capacitive device is charged by said charging current outputted by said current mirroring circuit;
• a switch coupled to said capacitive device for allowing said charging current outputted by said current mirroring circuit to charge said capacitive device and for discharging said capacitive device to ground;
• a first comparator having a first input coupled to a threshold voltage source and a second input coupled to said capacitive device for signalling when said voltage generated by said capacitive device reaches a level of said threshold voltage source;
• a second comparator having a first input coupled to a voltage source indicating a starting voltage level and a second input coupled to said capacitive device for signalling when said voltage generated by said capacitive device reaches said starting voltage level;
• a flip flop having a first inverted input coupled to said first comparator and a second inverted input coupled to said second comparator for generating an output signal when said voltage generated by said capacitive device is greater than said starting voltage level and less than said level of said threshold voltage source, said output signal of said flip flop having a pulse width which is proportional to said output reading of said sensor device;
• and
• pulse generator having an input coupled to an inverted output of said first comparator for generating a constant pulse width and an output coupled to said switch which causes said switch to close to completely discharge said capacitive device to ground when said voltage generated by said capacitive device reaches said level of said threshold voltage source.