I'd like to build a very simple interface to enable a standard cellphone to communicate with a PIC.
I think it should be possibile just by using the audio output: almost all modern, although cheap, cellphones are able to play MIDI files; this results in having a sinusoidal low-frequency signal on the headset port.
I'd like to connect this port to a PIC, in such a way the PIC can see if the signal is present or not; this way, by properly modulating the timing of the emitted audio, I can send binary data to the PIC! (sound present = 1, no sound = 0).
I think a simple RC circuit should be enough to turn the sinusoid into an almost-constant voltage value.
But I don't know how to read an analog voltage with a PIC, I only used it for digital projects.
Can anybody drive me in the right direction?
How is the ADC port named? How do I access it in assembly, or in Proton PIC BASIC? How do I compare its value to a fixed value?
I think it should be possibile just by using the audio output: almost all modern, although cheap, cellphones are able to play MIDI files; this results in having a sinusoidal low-frequency signal on the headset port.
I'd like to connect this port to a PIC, in such a way the PIC can see if the signal is present or not; this way, by properly modulating the timing of the emitted audio, I can send binary data to the PIC! (sound present = 1, no sound = 0).
I think a simple RC circuit should be enough to turn the sinusoid into an almost-constant voltage value.
But I don't know how to read an analog voltage with a PIC, I only used it for digital projects.
Can anybody drive me in the right direction?
How is the ADC port named? How do I access it in assembly, or in Proton PIC BASIC? How do I compare its value to a fixed value?