This is a simple demo of the dsp module. This module reads the value stored
in plc points, aplies mathematical functions to these values, and stores
the results in other plc points.

 The dsp module is divided into function blocks. Each function block aplies a
certain mathematical function to its inputs. Each function block uses one (or
more) plc points as inputs, and stores it's results in one (or more) plc 
points. By configuring a function block that uses as its input the output of a
previous function block one can implement complex mathematical functions. Closed
loop controllers are also allowed.

 Every function block uses plc points in the f32 (32 bit floating point) format 
for both input and output. The typeconv function block may be used to convert
values in other formats to the f32 format, and vice-versa. 

 This demo implements a closed loop PID controller. Use the 0-9 keys to change
the value of the leader, and watch the follower reach the same value. The alarm
function block is used to set three alarms, depending on the value of the error.
A nonlinear block is also used just for demonstartion purposes that applies
a deadband to the output of the PID controller from 4 to 5, and limits the
values to the range [2, 7] 

To start:
	cd demo/basic; make

To quit:
	press `Q' on the keyboard

The demo terminates when the `quit' point comes on (keyboard Q).


Notes:
	- kbd.c should eventually be replaced by a proper curses-based HMI thing
	- `demo' itself should be done in a generic fashion, rather than by
	  hard-coding all the modules; every program will need something to
	  start up all the modules at the beginning and shut them all down
	  at the end (perhaps giving them time to shut themselves down if
	  they want to).