Rotary Decoders; I/O Command Lists - Matrox Indio Installation And Hardware Reference

56 Chapter 4: Matrox Indio hardware reference

Rotary decoders

Matrox Indio features two rotary decoders (quadrature decoders). They are used
to decode quadrature input received from a rotary encoder with quadrature
E
output. A rotary encoder is a device that provides information about the position
and direction of a rotating shaft (for example, that of a conveyor belt). The encoder
outputs a two-bit code (also known as Gray code) on two wires for each change
in position of the rotating shaft; for a given direction of the rotating shaft, the
rotary encoder outputs the code in a precise sequence (either 00 - 01 - 11 - 10 or
00 - 10 - 11 - 01, depending on how the rotary encoder is attached to the rotating
shaft). If the rotating shaft changes direction, the rotary encoder transmits the
Gray code in the reverse sequence (00 - 10 - 11 - 01 or 00 - 01- 11 - 10,
respectively). The Matrox Indio rotary decoders can receive quadrature input
along any two specified auxiliary input signals.
The rotary decoder supports encoder frequencies of up to 2 KHz.
Note that an external source must be used to power the rotary encoder (for
example, your computer's 5 V power source).
You can configure the rotary decoder's settings, using the MIL-Lite function
MsysControl() with M_ROTARY_ENCODER...

I/O command lists

Matrox Indio has two I/O command lists, each of which allow you to schedule
commands to change the state of a bit of an I/O command register at a specified
time or counter value. You can route the state of the bit to an auxiliary output
signal to control a connected device at a required moment; the state of the bits
can be routed to any of the auxiliary output signals or can be used, for example,
to trigger a timer. You can use an I/O command list, for example, when multiple
parts are traveling between a sensor and one or more ejector(s) and you need to
schedule the ejection/redirection of the different parts based on some analysis.
To offset the moment at which a command should occur, each I/O command list
has 4 reference latches. Latches are used to store a timestamp or counter value
upon the specified transition of a specified signal. You can then use this timestamp
or counter value to schedule commands relative to this event.