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44 Chapter 2: Getting started with your Matrox 4Sight GPm unit
Using the auxiliary I/O interface
If you want to start or stop an external event based on some calculation or analysis,
you can manually set the state of any auxiliary output signal. To do so, you set the
state (on/off ) of a bit in a user settable register (static-user-output register). When
the bit is on, the circuit of the corresponding auxiliary output signal is grounded
and the current flows from the connected device to your Matrox 4Sight GPm;
when the bit is off, the circuit of the signal is open (the observed voltage will be
pulled high if pulled high by the connected circuitry). This bit is referred to as a
user-bit. To change the state of an auxiliary output signal using a user-bit, use the
MIL-Lite function MsysControl() with M_IO_SOURCE and M_USER_BITn;
to set the state of a user-bit, use MsysControl() with M_USER_BIT_STATE.
Your application can also act upon and interpret the state of an auxiliary input
signal. The state of an auxiliary input signal is not associated with a user-bit; you
poll the state of the signal directly. To poll the state of an auxiliary input signal,
use MsysInquire() with M_IO_STATUS. The state of an auxiliary input signal
can also generate an interrupt; to do so, use MsysControl() with
M_IO_INTERRUPT_STATE and then use MdigHookFunction() with
M_IO_CHANGE to hook a function to this event (that is, to set up an event
handler).
Connecting a stereo audio device
You can connect a stereo audio device to the audio input and output connectors,
using a 1/8" mini audio input/output plug. The audio interface is only designed
for line input/output operations. Since there is no output amplifier or input
preamplifier, the interface does not support speakers or microphones.
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