This example shows pre- and post-triggering of a signal-triggered Simulink® Real-Time™ host scope. After the script builds and downloads the oscillator model, xpcosc, to the target computer, it adds a scope of type 'host' to the real-time application and the signals 'Integrator1' and 'Signal Generator' to the scope. The scope is then configured to trigger on the signal 'Signal Generator' when it reaches 0.0 on a rising slope (signal value goes negative to positive). Pre-triggering is set to 12 samples, meaning that the 12 samples collected prior to the trigger are also stored in the host scope data vector.
Once the trigger condition is met, the scope is monitored to determine when its data acquisition is complete. Next, the scope data is uploaded to the development computer and plotted. This process repeats 25 times. After every fifth run, the damping gain 'Gain1/Gain' is set to a new random value (between 0 and 2000) and the scope toggles between a 12 sample pre-trigger and post-trigger mode.
Rationale for choosing 12 samples: The model sample time is 250 usec. Since the decimation factor for the scope is set to 4, the difference between two acquired samples is 1 ms. The 'Signal Generator' block outputs a square wave at 20 Hertz (50 msec per wave). Therefore, the acquisition will be shifted by 12 ms (approximately 1/4 of a square wave) each time the scope is updated.
Use 'slrtpingtarget' to test the connection between the development and target computers.
if ~strcmp(slrtpingtarget, 'success') error(message('xPCTarget:examples:Connection')); end
Open the oscillator model, xpcosc. Under the model's configuration parameter Simulink Real-Time options settings, the system target file has been set to slrt.tlc. Hence, building the model will create an executable image, xpcosc.mldatx, that can be run on a computer booted with the Simulink Real-Time kernel.
Build the model and download the image, xpcosc.mldatx, to the target computer.
Configure for a non-Verbose build.
Build and download application.
set_param('xpcosc','RTWVerbose','off'); rtwbuild('xpcosc'); tg = slrt('TargetPC1'); load(tg,'xpcosc');
### Starting Simulink Real-Time build procedure for model: xpcosc Warning: This model contains blocks that do not handle sample time changes at runtime. To avoid incorrect results, only change the sample time in the original model, then rebuild the model. ### Successful completion of build procedure for model: xpcosc ### Created MLDATX ..\xpcosc.mldatx ### Looking for target: TargetPC1 ### Download model onto target: TargetPC1
This code accomplishes a number of tasks.
Task 1: Create Target Object
Create the MATLAB® variable, tg, containing the Simulink Real-Time target object. This object contains the information required to communicate with and control the target computer.
Create a Simulink Real-Time target object
Set sample time to 250us
Set stop time to a high value (10000s)
Start model execution
Task 2: Create, configure, and plot to the host scope during each run.
Get index of parameter 'Gain1/Gain'
Get index of signal 'Integrator1'
Get index of signal 'Signal Generator'
Define (add) a host scope object
Add signals to signal list of scope object
Set number of samples
Set decimation factor
Set trigger mode
Set trigger signal to 'Signal Generator'
Set trigger level
Set trigger slope
Set pre-triggering to 12 samples
Task 3: Check for Plot Figure
Does the plot figure exist?
If no, create figure
If yes, make it the current figure
Task 4: Loop to acquire 25 data packages from the scope object.
Change parameter Gain1/Gain every fifth acquisition loop to a random value between 0 and 2000.
Toggle between pre- and post-triggering
Start scope object
Task 5: Wait until scope object has 'finished' state.
Create time vector, upload scope data and display it.
Upload time vector
Upload acquired data and plot
tg = SimulinkRealTime.target; % create target object tg.SampleTime = 0.000250; tg.StopTime = 10000; start(tg); tPar = getparamid(tg, 'Gain1', 'Gain'); % get indexes signals(1) = getsignalid(tg, 'Integrator1'); signals(2) = getsignalid(tg, 'Signal Generator'); sc = addscope(tg, 'host'); % define scope object addsignal(sc, signals); sc.NumSamples = 200; sc.Decimation = 4; sc.TriggerMode = 'Signal'; sc.TriggerSignal = signals(2); sc.TriggerLevel = 0.0; sc.TriggerSlope = 'rising'; sc.NumPrePostSamples = -12; figh = findobj('Name', 'scprepostdemo'); % check for plot figure if isempty(figh) figh = figure; set(figh, 'Name', 'scprepostdemo', 'NumberTitle', 'off'); else figure(figh); end m = 1; flag = 0; % loop to acquire data packages for n = 1 : 25 if isempty(find(get(0, 'Children') == figh, 1)), flag = 1; break; end if ~m setparam(tg, tPar, 2*1000*rand); sc.NumPrePostSamples = -sc.NumPrePostSamples; end m = rem(m + 1, 5); start(sc); while ~strcmpi(sc.Status,'finished'), end; % wait for scope finished t = sc.Time; plot(t, sc.Data); if (sc.NumPrePostSamples < 0) textString = '(Pre-Triggered)'; else textString = '(Post-Triggered)'; end title(['scprepostdemo: ', num2str(n), ' of 25 data packages ' textString]); set(gca,'XLim',[t(1), t(end)], 'YLim', [-10, 10]); drawnow; end if ~flag, title('scprepostdemo: finished'); end
When done, stop the application and close the model.
Stop model Close model