I'm attempting to connect to Loconet(spec) to a PIC32, and I've found a circuit to connect to an Arduino, but I'm not sure what exactly it does:
Specifically, I don't know what the LM393N voltage comparator at the top middle of the schematic does. I think that what is going on is that the LM393N is clamping the voltage to a certain level, between 0 and 5V or so in order for a microcontroller to read it as either a 0 or 1. I'm assuming that because of the following statements in the spec, as well as the given that VCC=5v:
Page 3: a) High = 1 = "MARK" : LOCONET+/- voltage above +4.0 Volts with respect to ground conductors. b) Low =0 = "SPACE" : LOCONET+/- voltage below +4.0 Volts with respect to grounds. c) The data should be received with 1.0 volt of HYSTERESIS centered on +4.0 volts. d) Maximum LOCONET+/- high voltage is +24V and nominal is +12V
I've seen another circuit that is similar, but uses an opto-isolator after the voltage comparator to actually interface with the microcontroller, which I'm assuming will then drop the voltage down to CMOS levels if it isn't already.
BONUS QUESTION: The LM393N in the center doesn't appear to be connected to anything, what's up with that?