Drawing Graphs Using @Plot Windows

The Plot Window can be used to display values from your board as a curve.

You instruct Visual Micro to plot a curve by using the @Plot keyword in a breakpoint Action (Read more about breakpoint actions here).

The following example shows a @Plot command in a breakpoint action field:

Simple @Plot command

 

If you start your sketch, a window will appear that plots the value of 'voltage' as a curve:

 

Simple curve

 

The Y axis will be scaled automatically, depending on the values coming in, so you won't have to adjust it. The curve will always fit into the chart.

Note IconNote:

By Default, the curve will only be updated if a new data point comes in, i.e. when a breakpoint with a @Plot action text is hit.
 If such breakpoints are only hit rarely or in irregular patterns, it might be better to switch to a fixed, timer controlled,  display update rate. Use the "Display" settings icon Display Plot Settings on the toolbar to change the display update rate.

The @Plot command

With the @Plot command, you are able to control the appearance of curves in a wide range. That's why it makes sense to take a closer look at the anatomy of the @Plot command:

 

Anatomy of the @Plot command

1
Don't forget to put curly brackets around the @Plot command
2
This is the @Plot keyword that instructs Visual Micro to create a plot window and to send the values to it
3
This gives your plot window a name. With this window name, you can control how many windows will open. If you have multiple @Plot commands with different windows names, Visual Micro will open multiple windows. All curves with the same window name will appear in the same window.
4
This gives the curve a name, in this example "Sensor"
5
This is the expression that shall be shown as a curve. You can use simple variables as well as more complex expressions etc., as described here.

 

Multiple Plot Windows

You can have multiple plot commands, either in separate breakpoints, one command per breakpoint, or in one breakpoint, one command after the other, like this:

{@Plot.MyPlotWindow.Sensor.Green voltage} {@Plot.MyPlotWindow.Temp.Blue temperature}

As mentioned under 3 above, the window name controls, to which window the value will be sent.
Example: These three @Plot commands will create one window with three curves:

{@Plot.MyPlotWindow.Sensor.Green voltage}

{@Plot.MyPlotWindow.Temp.Blue temperature}

{@Plot.MyPlotWindow.Direction.Green direction}



These commands will create three separate plot windows with one curve each:

{@Plot.MyFirstPlotWindow.Sensor.Green voltage}

{@Plot.MySecondPlotWindow.Temp.Blue temperature}

{@Plot.MyThirdPlotWindow.Direction.Green direction}

Plot Window Settings

The four buttons in the toolbar of the plot window can be used to change the plot window's appearance and behavior.

Display Plot Settings  Lets you set display properties, like the display refresh rate, line width of all curves, etc. (*)

Curve Plot Settings  Let's you specify the curve appearance, like curve color, curve line ticks, and the curve's name as displayed in the chart (*)

X Axis Plot Settings  Lets you specify properties of the X axis, like sweep time, and time format. (*)

Trigger Plot Settings  Lets you configure the trigger function, see explanation below

(*) Get more information from the balloon help windows that show up if you hover the mouse over a settings fields.

 

Plot Multichart Icon  Lets you switch between two different views: A view where all curves share the same chart, and a view where curves are drawn in their own chart under each other:

Plot Single Chart          Plot Multiple Charts

If your values have very different ranges of Y axis values, it makes sense to choose multiple chart view, because then each curve will have its own Y axis scaling. One example is an analog signal ranging from 0 to 1023, and a binary signal that only can have the values 0 and 1. If they were plotted in the same chart, you wouldn't be able to see the binary signal, because, due to the Y axis scaling, it would look like a flat line.

Triggers: Controlling when plotting starts

The plot window's trigger function works much like a trigger on an oscilloscope. It lets you control when the window starts to record and plot values. For example, if you are only interested in the trend of the "voltage" curve after the "temperature" value has exceeded a certain limit, then you can specify "temperature" as a trigger.

The plot window will only start plotting after the specified "temperature" threshold has been exceeded. The temperature "triggers" the plot operation.

Specifying a trigger value

To specify a trigger, use the following ".Trigger" breakpoint syntax:

{@Plot.MyPlotWindow.Trigger temperature}


The ".Trigger" keyword will instruct the plot window not to draw the value, but to take it as the trigger value - provided that you have enabled the trigger function:

To enable triggering, open the trigger settings window by clicking on the Trigger Plot Settings toolbar icon:

Trigger settings 

 

   Enable trigger function    Check this box to enable triggering. If the box is unchecked, the curve plots unconditional
   Trigger Source    This shows the syntax for the trigger expression you must use in your breakpoint, also see above
   Trigger Condition    Here you can specify a trigger condition. If trigger signals come in, they will be checked against this condition. Only if the trigger condition is fulfilled will the plot window start.
If you choose "None", then the first trigger value received will trigger, regardless of the value.
   After first trigger occured    Here you can select, how the plot window reacts after the curve has reached the right edge of the chart.
You can either tell the window to stop and wait in a new trigger value, or to continue drawing.
   Last value received    This shows the last value of the trigger expression that was received.
   Result    This shows the state of the chart trigger:

Trigplain Q  The chart is waiting on the arrival of a trigger signal

Trigtriggered Spark  The chart has received the trigger signal, which met the trigger condition.
The spark symbol lights up at the moment the trigger signal is received.

Triguntriggered Spark  The chart has received the trigger signal, which did not meet the trigger condition.
The spark symbol lights up at the moment the trigger signal is received.

The same indicator is located on the right edge of the plot window's toolbar.

Freezing a Plot Window

With the freeze icon  Plot Freeze Icon  on the toolbar, you can temporarily freeze the window. The data acquisition will continue in the background. With a second click on the icon, you unfreeze the plot window again.

Saving Chart as Images or Printing Charts

If you right click into a chart, a context menu appears that lets you copy the chart to the clipboard as a image, save it as a image or print it:

Plot Context Menu

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