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This directory contains the device entries for the RC Decoder.



HARDWARE
   The RC Decoder input from the RC radio is on the lowest numbered
pin on the connector (pin 2 or pin 10).  THE INPUT PIN MUST NOT BE
DRIVEN AT HIGHER THAN 3.3 VOLTS.  The next pin (4 or 10) is driven
high to indicate reception of valid RC data.  This pin normally is
tied to an LED through a 180 Ohm resistor.
   The remaining two pins on the connector are general purpose I/O
pins.


DEVICE NODES
   The device interfaces for the RC Decoder include the number or RC
channels to expect, the output of the RC decoder as well as the
direction and current value of the GPIO pins.

.../nchan
   The number of RC channels in the received signal.  A read-write
value given as as single ASCII digit in the range of two to eight
and terminated by a newline.  Write this as
        echo 6 > rcchan

.../rcdec
   This read-only node has the decoded RC signal as string of comma
separated channel times given in nanoseconds and terminated by a
newline.  Normally a new reading is available every 20 milliseconds.
There is no output if the input signal does not contain a valid RC
frame.

.../rcraw
   This read-only node is the raw output of the RC decoder.  It may
or may not contain a valid RC receive frame.  A frame can start any
time after a 3 millisecond period without any transitions.  A new
frame can start with either a transition from low to high or from
high to low.  The raw frame is printed as the initial value, that is
a 1 or a 0, followed by a comma separated list of times for each of
the high and low pulses in the frame.  Times are in hundreds of
nanoseconds.  That is a value of 10455 represents an interval of
1045500 nanoseconds or 1.04 milliseconds.

.../gpiodir
   The direction of the two GPIO pins as a single numeric digit
followed by a newline.  A value of 0 make both lines an input and
a value of 3 makes both lines an output.  A value of 2 make the
lower numbered GPIO pin (pin 6 or pin 14) an output and a value of
1 makes the higher numbers pin (8 or 16) an output.

.../gpioval
   The value on the GPIO pins.  Write to this device node to set
an output and read from it to get the current value on the pins.
A read requires a round trip over the USB-serial link and may take
a few milliseconds.  In time critical applications you may want to
use select() to wait for the data.  The LSB of the return value is
the value on the highest numbered pin (pin 8 or pin 16).