Does anyone know of some example code implementing an interrupt driven
hardware serial port read/write routine for any of the PIC16Xxxx devices
with hardware serial ports?

Let me give a little background.  I am working on an application with a
PIC16F876.  The PIC is decoding the quadrature signals from three optical
encoders. It communicates with a single board PC through a MAX232 chip at
9600 baud.  The quadrature signals will be coming at less than 1kHz.  The
PIC simply runs in a state machine, comparing the current channel states
with a list of valid states and increments/decrements a counter
accordingly.  It will loop at about 30kHz.  I chose not to use standard
encoder chips because of cost.  HP quadrature decoders are nearly $20
each in small quantities!  I am cleaning up the signals a little with a
schmitt trigger inveter on each channel.  I realize I may loose a count
or two every now and then due to noise, but this won't matter much.  If
it becomes a problem, I may add a requirement of 5 or so identical
consecutive readings before a change in position is registered.

The communication protocol is pretty simple--read a two byte command and
output 10 bytes of data with header, checksum, etc.  There are several
ways to implement the serial routine.  It seems to me that this would be
a good situation to use an interrupt. The PIC could continue looping
between bytes as the data is sent and received.  However, this is my
first program using interrupts in a PIC.  Can anyone point me to a
similar example?  I looked through the application notes but only found
something for a PIC17Xxxx device.  Am I on the right track, or is there
something I am missing?

Thanks,

Paul Brown

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