Using timers and rotary decoders with Matrox 4Sight GPm

See also

User Guide:

Timers and coordinating events Using quadrature input from a rotary encoder

Reference:

MdigControl MsysControl MsysGetHookInfo MsysHookFunction MsysInquire

Matrox 4Sight GPm has 16 timers and 2 rotary decoders that can be used to synchronize with external devices. Timers are used with I/O signals to coordinate events with external devices. Rotary decoders are used to decode quadrature input (2-bit Gray code derived from two signals) from a rotary encoder.

Timers

The 16 timers on Matrox 4Sight GPm can be configured using MsysControl(). The timers are configured in a similar way to what is described in the Timers and coordinating events section of Chapter 41: I/O signals and communicating with external devices. There are some differences, however, such as:

A timer arming mechanism can be configured and enabled for each timer. If timer arming is enabled, the timer will ignore its trigger signal (MsysControl() with M_TIMER_TRIGGER_SOURCE) until a signal transition, specified using MsysControl() with M_TIMER_ARM_ACTIVATION, occurs on the signal specified using MsysControl() with M_TIMER_ARM_SOURCE. To enable timer arming, use MsysControl() with M_TIMER_ARM.
The clock source can be specified for both the delay portion and duration portion of the timer output signal. For example, a rotary decoder output signal can be used to set the delay between the timer trigger and the active portion of the timer's output signal, and the unit's clock generator can be used to set the duration of the active portion of the timer's output signal.
The timer can measure the duration of a pulse on a signal. To enable this functionality, use MsysControl() with M_TIMER_USAGE set to M_PULSE_MEASUREMENT. When a timer is set in this mode, the duration of pulses that occur on the timer's trigger source (M_TIMER_TRIGGER_SOURCE) are measured with respect to the clock source for the active portion of the timer (M_TIMER_CLOCK_SOURCE). To measure active-high pulses, set M_TIMER_TRIGGER_ACTIVATION to M_LEVEL_HIGH; to measure active-low pulses, set M_TIMER_TRIGGER_ACTIVATION to M_LEVEL_LOW. The measured value can be inquired using MsysInquire() with M_TIMER_VALUE. Note that when in this mode, the timer's output always remains low, and the values set using M_TIMER_DELAY_CLOCK_SOURCE, M_TIMER_DELAY, and M_TIMER_DURATION are ignored.

Rotary decoders

The two rotary decoders on Matrox 4Sight GPm can be configured using MsysControl(). The rotary decoders are configured in a similar way to what is described in the Using quadrature input from a rotary encoder section of Chapter 41: I/O signals and communicating with external devices. However, the following settings are unavailable when using Matrox 4Sight GPm: setting the direction of movement (M_ROTARY_ENCODER_DIRECTION), setting a signal source that changes the rotary decoder counter value (M_ROTARY_ENCODER_FORCE_VALUE_SOURCE), setting whether to enable the rotary decoder to store the counter value at the end of the last grab or frame interrupt (M_ROTARY_ENCODER_FRAME_END_READ), and setting a multiplying factor to each increment/decrement of the rotary decoder counter (M_ROTARY_ENCODER_MULTIPLIER).

There are two data latches associated with the rotary decoders on Matrox 4sight GPm. You can store the counter value of a rotary decoder in either of these data latches whenever a signal is received from a timer or auxiliary I/O, using MsysControl() with settings from the table For controlling the settings of a data latch associated with rotary encoders. You can retrieve the stored value within a hook function (hooked using MsysHookFunction()) using MsysGetHookInfo() with M_SYS_DATA_LATCH_VALUE.

Note that the function must be hooked to the same type of event that triggers the latch. For example, if the latch is triggered by a timer (M_SYS_DATA_LATCH_TRIGGER_SOURCE with M_TIMERn), the hook function must be hooked to a timer event (M_TIMER_START or M_TIMER_END).