Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
learn:instrumentation:tutorials:analog-discovery-studio-using-cross-triggers [2019/08/22 19:38] – [2. What is Cross Triggering?] Arthur Brown | learn:instrumentation:tutorials:analog-discovery-studio-using-cross-triggers [2020/07/28 17:28] – Arthur Brown | ||
---|---|---|---|
Line 1: | Line 1: | ||
- | ====== Using Cross Triggering ====== | + | ====== Using Cross Triggering |
- | ==== Introduction ==== | + | <WRAP round important 660px> |
- | + | This guide has been replaced by [[learn/ | |
- | When using Test and Measurement devices, understanding " | + | </ |
- | + | ||
- | ---- | + | |
- | ==== Prerequisites ==== | + | |
- | + | ||
- | * One or more Digilent Test & Measurement Devices with Analog I/O and/or Digital I/O | + | |
- | * **Note**: //Users without a device may still find this guide informative// | + | |
- | * A Computer with [[reference: | + | |
- | * Basic familiarity with WaveForms' | + | |
- | + | ||
- | ---- | + | |
- | + | ||
- | //Before discussing any examples, it is important to understand what a trigger is and why a trigger is helpful. The following sections will define triggers as an acquisition tool and describe what triggers do to make signal analysis more effective.// | + | |
- | + | ||
- | ==== 1. What is a Trigger? | + | |
- | //What is a trigger? How is one set up?// | + | |
- | + | ||
- | --> Click Here to Learn the Answer# | + | |
- | + | ||
- | - **Trigger Systems**: A trigger system works with an oscilloscope, | + | |
- | - **Trigger Types**: There are many different types of triggers, all having their own strengths, depending on application, | + | |
- | - **Trigger Modes**: There are a few different modes that a trigger can operate under and these modes determine if the oscilloscope will display a waveform if a trigger is not detected. This tutorial covers “normal” and “auto” modes. In **normal** mode, the acquisition tool only collects voltage data over some time period (also called a sweep) if the input signal satisfies the trigger definition. Otherwise, the acquisition tool will either display a blank screen or remain static displaying the last acquisition. In **auto** mode, the acquisition tool sweeps with or without a trigger and uses a timer to sweep if there is no input signal. | + | |
- | - **Trigger Holdoff**: Trigger holdoff is an adjustable time period in which the acquisition instrument cannot generate a trigger. This can be very helpful with complex | + | |
- | + | ||
- | <-- | + | |
- | + | ||
- | ==== 2. How and Why Are Triggers Used? ==== | + | |
- | //Once set up, what does the trigger do to incoming data? How does this help the user?// | + | |
- | + | ||
- | --> Click Here to Learn the Answer# | + | |
- | + | ||
- | Triggers act like a comparator. With default settings or a user defined voltage level and slope (rising edge, falling edge, or either), when the input to the trigger system matches these settings, the trigger system sends a pulse to its output. This pulse is monitored by the acquisition instrument and another sub-system called a time-based interpolator. | + | |
- | + | ||
- | When the acquisition instrument sees this pulse from the trigger system, it begins to digitize, process, store, and measure this data. Before this waveform data can be displayed on the screen, the time-based interpolator figures out what address in the waveform buffer matches the defined trigger point and tells the acquisition instrument to display this data at time t=0.0 seconds. | + | |
- | + | ||
- | By repeatedly displaying similar sections of the input signal at a specified trigger point, a trigger helps display a dynamic waveform as a static image. Otherwise, the waveform would just race across the display in a way that would be hard to interpret and impossible to take measurements with. | + | |
- | + | ||
- | Triggers can also be helpful for capturing data around or locating an infrequent event. Some examples include digital pulses that are: missing, irregular in width, or not reaching valid logic high or low levels. | + | |
- | + | ||
- | <-- | + | |
- | ==== 3. What is Cross Triggering? ==== | + | |
- | //What makes a trigger a " | + | |
- | + | ||
- | --> Click Here to Learn the Answer# | + | |
- | + | ||
- | In the general sense, cross triggering describes systems where multiple instruments - often different devices - share trigger events. This can mean that either both instruments capture the signal containing the trigger event, or that when one of the instruments detects the trigger event, it generates a signal to trigger the other instrument. | + | |
- | + | ||
- | Since benchtop oscilloscopes traditionally only contain one instrument, cross triggering typically refers to sharing the same trigger between multiple devices. Because Digilent' | + | |
- | + | ||
- | <-- | + | |
- | + | ||
- | ---- | + | |
- | ==== 3. Examples of Cross Triggering Systems ==== | + | |
- | === 3.1 Cross Triggering between Instruments === | + | |
- | //This example demonstrates how using cross triggering makes it easier to change trigger sources across multiple instruments on a single device. A loopback circuit will be created that will connect the device' | + | |
- | + | ||
- | {{ learn: | + | |
- | + | ||
- | ---- | + | |
- | == 3.1.1 Hardware Setup == | + | |
- | <WRAP group>< | + | |
- | Connect the Digilent Test and Measurement device to the host computer. | + | |
- | + | ||
- | Connect the analog input channel 1 positive pin (1+, orange cable) to the waveform generator output channel 1 pin (W1, yellow cable). Then connect the analog input channel 1 negative pin (1-, orange and white cable) to ground (down arrow, black cable). Lastly, connect the external trigger 1 pin (TRIG 1, grey cable) to the digital input/output pin 0 (DIO 0, pink cable). | + | |
- | + | ||
- | The circuit achieved by these connections is a simple loopback, allowing the test and measurement device' | + | |
- | </ | + | |
- | {{ learn: | + | |
- | </ | + | |
- | ---- | + | |
- | == 3.1.2 Software Setup == | + | |
- | The following software setup is streamlined to focus on the External Trigger application. For more detailed help with the following instruments, | + | |
- | <WRAP group>< | + | |
- | Launch WaveForms, then open the following instruments: | + | |
- | - Open a new // | + | |
- | * Set the Channel // | + | |
- | * Set the //Trigger// source to // | + | |
- | * Set the //Wait// time to //none// | + | |
- | * Set the //Run// time to //1 ms// | + | |
- | * Set the //Repeat// count to // | + | |
- | * Leave all other settings as their defaults | + | |
- | - Open a new // | + | |
- | * Set the Trigger //Mode// to // | + | |
- | * Set the Trigger //Source// to //Wavegen 1// | + | |
- | * Ensure the Time // | + | |
- | * Set the Time //Base// to //1 ms/div// | + | |
- | * Ensure Channel 1's //Offset// is //0 V// | + | |
- | * Ensure Channel 1's //Range// is //500 mV/div// | + | |
- | * Disable Channel 2 by // | + | |
- | - Open a new // | + | |
- | * Configure DIO 0 to be a button that outputs 0 when released, and 1 when pressed | + | |
- | </ | + | |
- | {{ learn: | + | |
- | </ | + | |
- | + | ||
- | **Note:** //In order to show each of the opened instruments on the screen at once, click on the Docking Windows button ({{learn: | + | |
- | + | ||
- | ---- | + | |
- | == 3.1.3 Operating the Multi-Instrument Cross Trigger Example == | + | |
- | //Now that the workspace and hardware are set up, experimentation with the resulting system can begin.// | + | |
- | + | ||
- | Click the //Wavegen// and //Scope// instruments' | + | |
- | + | ||
- | <WRAP group>< | + | |
- | Click the //Manual Trigger// button in the bottom left-hand corner of the WaveForms application (marked in red in the image to the right) to trigger the //Wavegen// instrument to output a signal once. The signal plays back so quickly that the // | + | |
- | + | ||
- | Next, try modifying the //Wavegen// trigger' | + | |
- | </ | + | |
- | {{ learn: | + | |
- | </ | + | |
- | + | ||
- | <WRAP group>< | + | |
- | Next, change the //Wavegen// trigger' | + | |
- | + | ||
- | In conclusion, note that through each of these changes to the trigger configuration, | + | |
- | + | ||
- | Further information regarding the trigger configuration options available in each instrument can be found in their respective "Using the ..." guides (linked above), or through the [[reference: | + | |
- | </ | + | |
- | {{ learn: | + | |
- | </ | + | |
- | ---- | + | |
- | === 3.2 Cross Triggering between Devices === | + | |
- | //This example demonstrates a simple approach to comparing data captured using two devices at once. A circuit will be created between two Digilent | + | |
- | + | ||
- | {{ learn: | + | |
- | + | ||
- | ---- | + | |
- | == 3.2.1 Hardware Setup == | + | |
- | + | ||
- | <WRAP group>< | + | |
- | Connect two Digilent Test and Measurement devices to the computer. Two Analog Discovery 2s were used in creating this document, but any WaveForms compatible device with analog inputs and outputs will work. If the devices require external power, plug them in and turn them on. | + | |
- | + | ||
- | Make the following connections between the two devices' | + | |
- | * Connect each device' | + | |
- | * Connect each device' | + | |
- | * Connect a ground pin from each device to a ground pin from the other device (down arrow, black). | + | |
- | * Connect each device' | + | |
- | + | ||
- | See the block diagram to the right for a visual representation of these connections. | + | |
- | + | ||
- | **Note:** //The connections are symmetrical, | + | |
- | </ | + | |
- | {{ : | + | |
- | </ | + | |
- | + | ||
- | ---- | + | |
- | == 3.2.2 Software Setup == | + | |
- | 1. Open two instances of WaveForms. | + | |
- | + | ||
- | 2. Use each WaveForms instance' | + | |
- | + | ||
- | **Note:** //In order to show each of the opened instruments on the screen at once, click on the Docking Windows button ({{learn: | + | |
- | + | ||
- | <WRAP group>< | + | |
- | 3. In one WaveForms instance, henceforth referred to as the " | + | |
- | * Open a new // | + | |
- | * Set the Time //Base// to //500 us/div// | + | |
- | * Set the Trigger //Mode// to // | + | |
- | * Set the Trigger //Source// to //External 1// | + | |
- | * Set the Trigger // | + | |
- | * Disable Channel 2 by // | + | |
- | * Open a new // | + | |
- | * Set the Channel // | + | |
- | * Set Channel 1's //Trigger// Source to //External 1// | + | |
- | * Set Channel 1's //Wait// Time to //none// | + | |
- | * Set Channel 1's //Run// Time to //2ms// | + | |
- | * Set Channel 1's Simple Wave // | + | |
- | * Set Channel 1's Simple Wave //Type// to //Sine// | + | |
- | * Open a new // | + | |
- | * Configure DIO 0 to be a button that outputs " | + | |
- | * Open a new // | + | |
- | </ | + | |
- | {{ : | + | |
- | </ | + | |
- | + | ||
- | <WRAP group>< | + | |
- | 4. In the other WaveForms instance, henceforth referred to as the " | + | |
- | * Open a new // | + | |
- | * Set the Time //Base// to //500 us/div// | + | |
- | * Set the Trigger //Mode// to // | + | |
- | * Set the Trigger //Source// to //External 1// | + | |
- | * Set the Trigger // | + | |
- | * Disable Channel 2 by // | + | |
- | * Open a new // | + | |
- | * Set the Channel // | + | |
- | * Set Channel 1's Trigger to //External 1// | + | |
- | * Set Channel 1 //Wait// Time to //none// | + | |
- | * Set Channel 1 //Run// Time to //2 ms// | + | |
- | * Set Channel 1 Simple Wave // | + | |
- | * Set Channel 1 Simple Wave //Type// to // | + | |
- | * Open a new // | + | |
- | </ | + | |
- | {{ : | + | |
- | </ | + | |
- | <WRAP group>< | + | |
- | 5. Copy the code to the right into the **primary** instance' | + | |
- | </ | + | |
- | < | + | |
- | // Create a reference channel to contain the imported acquisition | + | |
- | var r = Scope.Ref1.Range.value | + | |
- | var o = Scope.Ref1.Offset.value | + | |
- | Scope.Ref1.Clone(Scope.Channel1) | + | |
- | Scope.Ref1.Range.value = r | + | |
- | Scope.Ref1.Offset.value = o | + | |
- | // Open the file exported by the secondary instance | + | |
- | var f = File(" | + | |
- | // Wait for the other instance to finish saving data | + | |
- | for(var i = 0; i < 1000 && !f.exist(); i++); | + | |
- | // Read data from the file and save it into the reference channel | + | |
- | var rg = f.readDouble() | + | |
- | f.deleteFile() | + | |
- | Scope.Ref1.data = rg | + | |
- | }</ | + | |
- | </ | + | |
- | <WRAP group>< | + | |
- | 6. Copy the code to the right into the **secondary** instance' | + | |
- | </ | + | |
- | < | + | |
- | // Create a binary file and write the channel 1 acquisition into it | + | |
- | var f = File(" | + | |
- | f.writeDouble(Scope.Channel1.alldata) | + | |
- | }</ | + | |
- | </ | + | |
- | + | ||
- | ---- | + | |
- | == 3.2.3 Operating the Multi-Device Cross Trigger Example == | + | |
- | + | ||
- | //Now that the workspaces and hardware are set up, experimentation with the resulting system can begin.// | + | |
- | + | ||
- | This multi-device system connects the //Wavegen// and //Scope// instruments of the two devices together, so that all are triggered by the same external trigger, sourced from the **primary** device' | + | |
- | + | ||
- | ---- | + | |
- | <WRAP group>< | + | |
- | To capture data, first, click the **Run** button in each //Scope// and //Wavegen// instrument. Then, click the **primary** instance' | + | |
- | </ | + | |
- | {{ : | + | |
- | + | ||
- | {{ : | + | |
- | </ | + | |
- | ---- | + | |
- | <WRAP group>< | + | |
- | To view data captured by each device in the same plot, click the **Run** button in the **secondary** instance' | + | |
- | </ | + | |
- | {{ : | + | |
- | </ | + | |
- | ---- | + | |
- | + | ||
- | Using multi-device systems like this allows a user to greatly extend the number of analog signals that can be captured at once. For the Analog Discovery 2, each additional device adds another two analog input and output channels to the overall system, and digital I/O could easily be added as well. While the two captures are not perfectly aligned (each device runs on its own oscillator), | + | |
- | + | ||
- | The WaveForms application was not designed to support more than one device at a time. However, WaveForms SDK is available for users that want to develop their own applications, | + | |
- | + | ||
- | ---- | + | |
- | ==== Next Steps ==== | + | |
- | + | ||
- | Especially when using multiple devices, the calibration (or lack thereof) of the devices may affect the ability to compare acquired data. For more information on calibrating your Test and Measurement device, see the [[learn: | + | |
- | + | ||
- | For more guides on how to use the Digilent Test & Measurement Device, return to the device' | + | |
- | + | ||
- | For more information on WaveForms, visit the [[reference: | + | |
- | + | ||
- | For technical support, please visit the [[https:// | + | |
- | + | ||
- | {{tag> | + | |
+ | {{tag> |