I dont think you can even use the modulation technique in this instance because its the slave device he wants sending the data (i.e. the device that doesnt have a power supply).
You can use the mondulation technique if you were transmitting data from the master to the slave, but not slave to master.
If you already have 2 wires between the 2 devices, whats so hard about running a 3rd wire for data?
I beg to differ.
The data would be used to turn on and off a carrier which would become an AC signal. This can be superimposed on top of a DC signal quite easily.
It doesnt matter which direction power or data are heading. They simply use the same piece of wire as their connection.
A phantom powered electret microphone effectively does what is requested here. Power is fed from the mixer (MASTER) whilst the audio (or Data) is fed along the exact same wires by the Microphone (SLAVE).
See attached diagram for how data and power would be connected. I havent draw the modulator and demodulator as I dont have a suitable design to hand but generating the signal could be as easy as running the PWM on the SLAVE PIC ad using a transistor driven the the TX data pin to modulate it. At the MASTER end you would need a circuit to detect the carrier and provide a logic level to drive the RX data pin on the Master Pic.
The inductors allow DC power to pass but block the AC carrier so that PSU compoments dont attenuate the carrier.
The capacitors allow the AC carrier to pass but block the DC supply voltage.
Originally Posted by Kamikaze47
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