Doing More with Analog Input (Data Acquisition Toolbox)

Data Acquisition Toolbox

Device-Specific Hardware Triggers

Many data acquisition devices possess the ability to accept a hardware trigger. Hardware triggers are processed directly by the hardware and can be either a digital signal or an analog signal. Hardware triggers are often used when speed is required because a hardware device can process an input signal much faster than software.

The device-specific hardware triggers are presented to you as additional property values. Hardware triggers for Agilent Technologies, Measurement Computing, and National Instruments devices are discussed below and in Base Property Reference.

Note that the available hardware trigger support depends on the board you are using. Refer to your hardware documentation for detailed information about its triggering capabilities.

Agilent Technologies

When using Agilent Technologies hardware, there are additional trigger types and trigger conditions available to you. These device-specific property values fall into two categories: hardware digital triggering and hardware analog triggering.

The device-specific trigger types and trigger conditions are described below and in Base Property Reference.

Table 5-8: Analog Input TriggerType and TriggerCondition Property Values for Agilent Hardware
TriggerType Value
TriggerCondition Value
Description

HwDigital
{PositiveEdge}
The trigger occurs when the positive (rising) edge of a digital signal is detected.

NegativeEdge
The trigger occurs when the negative (falling) edge of a digital signal is detected.

HwAnalog
{Rising}
The trigger occurs when the analog signal has a positive slope when passing through the specified range of values.

Falling
The trigger occurs when the analog signal has a negative slope when passing through the specified range of values.

Leaving
The trigger occurs when the analog signal leaves the specified range of values.

Entering
The trigger occurs when the analog signal enters the specified range of values.

**Table 5-8: Analog Input TriggerType and TriggerCondition Property Values for Agilent Hardware**
TriggerType Value	TriggerCondition Value	Description
`HwDigital`	`{PositiveEdge}`	The trigger occurs when the positive (rising) edge of a digital signal is detected.
`NegativeEdge`	The trigger occurs when the negative (falling) edge of a digital signal is detected.
`HwAnalog`	`{Rising}`	The trigger occurs when the analog signal has a positive slope when passing through the specified range of values.
`Falling`	The trigger occurs when the analog signal has a negative slope when passing through the specified range of values.
`Leaving`	The trigger occurs when the analog signal leaves the specified range of values.
`Entering`	The trigger occurs when the analog signal enters the specified range of values.

Note that when TriggerType is HwAnalog, the trigger condition values are all specified as two-element vectors. Setting two trigger levels prevents the module from triggering repeatedly because of a noisy signal.

Hardware Digital Triggering. If TriggerType is HwDigital, the trigger is given by a digital (TTL) signal. For example, to trigger your acquisition when the negative edge of a digital signal is detected

ai = analoginput('hpe1432',8);
addchannel(ai,1:16);
set(ai,'TriggerType','HwDigital');
set(ai,'TriggerCondition','NegativeEdge');

Hardware Analog Triggering. If TriggerType is HwAnalog, the trigger is given by an analog signal. For example, to trigger your acquisition when the trigger signal is between -4 volts and 4 volts

ai = analoginput('hpe1432',8);
addchannel(ai,1:16);
set(ai,'TriggerType','HwAnalog');
set(ai,'TriggerCondition','Entering');
set(ai,'TriggerConditionValue',[-4.0 4.0]);
set(ai,'TriggerChannel',ai.Channel(1:4));

Measurement Computing

When using Measurement Computing hardware, there are additional trigger types and trigger conditions available to you. These device-specific property values fall into two categories: hardware digital triggering and hardware analog triggering.

The device-specific trigger types and trigger conditions are described below and in Base Property Reference.

Table 5-9: Analog Input TriggerType and TriggerCondition Values for MCC Hardware
TriggerType Value
TriggerCondition Value
Description

HwDigital
GateHigh
The trigger occurs as long as the digital signal is high.

GateLow
The trigger occurs as long as the digital signal is low.

TrigHigh
The trigger occurs when the digital signal is high.

TrigLow
The trigger occurs when the digital signal is low.

TrigPosEdge
The trigger occurs when the positive (rising) edge of the digital signal is detected.

{TrigNegEdge}
The trigger occurs when the negative (falling) edge of the digital signal is detected.

HwAnalog
{TrigAbove}
The trigger occurs when the analog signal makes a transition from below the specified value to above.

TrigBelow
The trigger occurs when the analog signal makes a transition from above the specified value to below.

GateNegHys
The trigger occurs when the analog signal is more than the specified high value. The acquisition stops if the analog signal is less than the specified low value.

GatePosHys
The trigger occurs when the analog signal is less than the specified low value. The acquisition stops if the analog signal is more than the specified high value.

GateAbove
The trigger occurs as long as the analog signal is more than the specified value.

GateBelow
The trigger occurs as long as the analog signal is less than the specified value.

GateInWindow
The trigger occurs as long as the analog signal is within the specified range of values.

GateOutWindow
The trigger occurs as long as the analog signal is outside the specified range of values.

**Table 5-9: Analog Input TriggerType and TriggerCondition Values for MCC Hardware**
TriggerType Value	TriggerCondition Value	Description
`HwDigital`	`GateHigh`	The trigger occurs as long as the digital signal is high.
`GateLow`	The trigger occurs as long as the digital signal is low.
`TrigHigh`	The trigger occurs when the digital signal is high.
`TrigLow`	The trigger occurs when the digital signal is low.
`TrigPosEdge`	The trigger occurs when the positive (rising) edge of the digital signal is detected.
`{TrigNegEdge}`	The trigger occurs when the negative (falling) edge of the digital signal is detected.
`HwAnalog`	`{TrigAbove}`	The trigger occurs when the analog signal makes a transition from below the specified value to above.
`TrigBelow`	The trigger occurs when the analog signal makes a transition from above the specified value to below.
`GateNegHys`	The trigger occurs when the analog signal is more than the specified high value. The acquisition stops if the analog signal is less than the specified low value.
`GatePosHys`	The trigger occurs when the analog signal is less than the specified low value. The acquisition stops if the analog signal is more than the specified high value.
`GateAbove`	The trigger occurs as long as the analog signal is more than the specified value.
`GateBelow`	The trigger occurs as long as the analog signal is less than the specified value.
`GateInWindow`	The trigger occurs as long as the analog signal is within the specified range of values.
`GateOutWindow`	The trigger occurs as long as the analog signal is outside the specified range of values.

Hardware Digital Triggering. If TriggerType is HwDigital, the trigger is given by a digital (TTL) signal. For example, to trigger your acquisition when the positive edge of a digital signal is detected:

ai = analoginput('mcc',1);
addchannel(ai,0:7);
set(ai,'TriggerType','HwDigital')
set(ai,'TriggerCondition','TrigPosEdge')

The diagram below illustrates how you connect a digital trigger signal to a PCI-DAS1602/16 board. A/D External Trigger corresponds to pin 45.

ai = analoginput('mcc',1);
addchannel(ai,0:7);
set(ai,'TriggerType','HwAnalog');
set(ai,'TriggerCondition','GateInWindow');
set(ai,'TriggerConditionValue',[-4.0 4.0]);

The diagram below illustrates how you connect an analog trigger signal to a PCI-DAS1602/16 board. AI Ch 0-7 corresponds to pins 2-17, while Analog Trigger In corresponds to pin 43.

National Instruments

When using National Instruments (NI) hardware, there are additional trigger types and trigger conditions available to you. These device-specific property values fall into two categories: hardware digital triggering and hardware analog triggering.

The device-specific trigger types and trigger conditions are described below and in Base Property Reference.

Table 5-10: Analog Input TriggerType and TriggerCondition Property Values for NI Hardware
TriggerType Value
TriggerCondition Value
Description

HwDigital
None
The trigger occurs when the falling edge of a digital (TTL) signal is detected.

HwAnalogChannelor HwAnalogPin
{AboveHighLevel}
The trigger occurs when the analog signal is above the specified value.

BelowLowLevel
The trigger occurs when the analog signal is below the specified value.

HighHysteresis
The trigger occurs when the analog signal is greater than the specified high value with hysteresis given by the specified low value.

InsideRegion
The trigger occurs when the analog signal is inside the specified region.

LowHysteresis
The trigger occurs when the analog signal is less than the specified low value with hysteresis given by the specified high value.

**Table 5-10: Analog Input TriggerType and TriggerCondition Property Values for NI Hardware**
TriggerType Value	TriggerCondition Value	Description
`HwDigital`	`None`	The trigger occurs when the falling edge of a digital (TTL) signal is detected.
`HwAnalogChannel`or `HwAnalogPin`	`{AboveHighLevel}`	The trigger occurs when the analog signal is above the specified value.
`BelowLowLevel`	The trigger occurs when the analog signal is below the specified value.
`HighHysteresis`	The trigger occurs when the analog signal is greater than the specified high value with hysteresis given by the specified low value.
`InsideRegion`	The trigger occurs when the analog signal is inside the specified region.
`LowHysteresis`	The trigger occurs when the analog signal is less than the specified low value with hysteresis given by the specified high value.

Hardware Digital Triggering. If TriggerType is HwDigital, the trigger occurs when the falling edge of a digital (TTL) signal is detected. The following example illustrates how to configure a hardware digital trigger.

ai = analoginput('nidaq',1);
addchannel(ai,0:7);
set(ai,'TriggerType','HwDigital')

The diagram below illustrates how you connect a digital trigger signal to an MIO-16E Series board. PFI0/TRIG1 corresponds to pin 11.

Hardware Analog Triggering. If TriggerType is HwAnalogPin, the trigger is given by a low-range analog signal (typically between -10 and 10 volts) connected to the appropriate trigger pin. For example, to trigger your acquisition when the trigger signal is between -4 volts and 4 volts:

ai = analoginput('nidaq',1);
addchannel(ai,0:7);
set(ai,'TriggerType','HwAnalogPin')
set(ai,'TriggerCondition','InsideRegion')
set(ai,'TriggerConditionValue',[-4.0 4.0])

If TriggerType is HwAnalogChannel, the trigger is given by an analog signal and the trigger channel is the first channel in the channel group (MATLAB index of one). The valid range of the analog trigger signal is given by the full-scale range of the trigger channel. The following example illustrates how to configure such a trigger where the trigger channel is assigned the descriptive name TrigChan and the default TriggerCondition property value is used.

ai = analoginput('nidaq',1);
addchannel(ai,0:7);
set(ai.Channel(1),'ChannelName','TrigChan')
set(ai,'TriggerChannel',ai.Channel(1))
set(ai,'TriggerType','HwAnalogChannel')
set(ai,'TriggerConditionValue',0.2)

The diagram below illustrates how you can connect an analog trigger signal to an MIO-16E Series board.

When Did the Trigger Occur? Events and Callbacks