Rubin, Dan wrote:
> There isn't any publicly available (on the Internet, etc.) information out
> there describing the signal used by RC radios?

> My other burning question is can you build a receiver without any coils or
> other RF type circuitry?  In the snapshot of an existing product that uses
> the PIC (http://users.joplin.com/~bselman/rffs100.htm) there does not appear
> to be any RF circuitry and the crystal seems to be connected directly to the
> PIC?


There are two "signaling" layers to care about.
The highest (or lowest depending on how you look at it)
is the RF layer. It could be AM (on real old transmitters),
or FM. Then there is the actual "RC" signal that
is useed as the FM or AM modulating signal.

The most common "protocol" is a puls train with an equal
number of pulses as there are "channels" in the actual
tramsmitter. Each puls can be between 0.5 ms and 1.5 ms with
1.0 ms beeing "mid-position" (most common, there are others).
All controls uses this PWM coding, even "on/off" type of
switches on the transmitter. It's up to the receiver/decoder
to interpret each channel in a correct way.


Now a *receiver* has two functions. The first is to demodulate
the RF signal and re-create the puls-train. This is hardly
a task for the PIC, as far as I can see (rfPIC ?). There
must be ready built radio modules for this task.

The second task is to split the puls-train (PWM signal) into
separate channels. A parfect task for a PIC !

A ready-build RC-receiver integrates both the RF part and the
PWM decoding part.

I'd use a ready-built module for the RF parts, and concentrate
on the PWM pulse decoding on the PIC.

Jan-Erik.

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