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Using TestPoint to Send Commands via RS232 to ADR Interfaces

TestPoint  Application - Strip Chart Recorder with Alarm Indicator

1. Introduction

The following application  demonstrates how TestPoint can be used with ADR interfaces, or any ASCII based serial data acquisition and control interface. The application is a strip chart recorder with an alarm indicator using an ADR112 data acquisition and control interface.  It is assumed the user has a basic knowledge of TestPoint, however, no prior experience with TestPoint is required as long as the user manual is available to help with the generic tasks. Figure 1 shows our final operating panel for the application in operation. The panel displays the value of analog input 0   from the ADR112 and displays its value in three formats including, strip chart, bar graph and as a numeric value. A visual alarm indicator changes color from green to red when the analog input value exceeds a limit value entered by the user.

xfin2.gif (5413 bytes) Figure 1: Final Operating Panel

2. Lets Get Started

With TestPoint loaded, double-click the TestPoint icon to start the application. The screen shown in Figure 2 will appear.

tp2.gif (13339 bytes) Figure 2: TestPoint Start Screen

Begin by dragging objects required for the application from the stock window into your application. the required items are a switch switch.gif (1009 bytes) , graph graph.gif (252 bytes) , RS232 port com.gif (251 bytes) and a loop loop.gif (238 bytes). Position the objects as shown in Figure 3.

xtp1.gif (16815 bytes) Figure 3 : Initial Application Objects

Objects loaded into the application also appear as icons in the object list. Double-clicking and object in the object List or in the application will cause a menu to pop up and allow setting of parameters for that object. Figure 4 shows the graph being set to a " Strip Chart " mode. The Y axis was set to a range of 0 to 4096 to facilitate the 12-bit data from the ADR112. The X axis was configured to show 1000 samples in the chart window.

xtp2.gif (22328 bytes) Figure 4 : Editing Graph Properties

3. Programming

Before starting the programming we should have a clear understanding of  what the functions the application is to perform.  Our application will send an " RD0" command to an ADR112 on com2 causing the ADR112 to return an 12-bit number ( 0000 to 4095 ) depending on the voltage on AN0. The data is then graphed on a strip chart, displayed in numeric format and bar format, and lastly,  a high alarm limit is to be checked . This operation is to be repeated continuously ( free-running ). With the basic components for the application in place, and an understanding of the application,  programming can be started. This is where TestPoint leaves other GUI languages in the dust. To write the program, components are dragged from the object List into the action List. Depending on the object dragged into the action List, a pop-up menu appears to give a few options relating to that object. For example, our application requires use of the RS232 port and it must be opened and configured to 9600 baud to communicate with the ADR112.  If the RS232 icon is dragged and dropped into the action list a pop-up menu will appear as shown in Figure 5.  The appropriate action is then selected from the pop-up menu and then listed in the action list. This is repeated four times for our application. The first  to open the serial port, the second sets the mode of the port ( 9600 baud), the third outputs to the port (  RD0 command ) , and the fourth captures data from  the port ( ADR112 response to RD0 command ).

xtp3.gif (19448 bytes) Figure 5 : The Action List

With the four RS232 port "actions" in place, the graph is dragged into the action list and " Add Point to " is selected ( Figure 6, Line 6 ). The gray boxes in the action list are  user entered variables such as data, objects or settings. The RS232 object was dragged into line six to be selected as the source for the graph data.  A loop was then created by dragging the LOOP1 icon into the action list and dragging the Do Loop line to line 3 in the action list. There are still a few objects to add to the application, however, this would be a good time to run the application to test our program.

xtp4.gif (21221 bytes) Figure 6 : Ready for First Run

4. First time Through

Select MODE/RUN from the main menu bar and with the ADR112 connected to the com port and powered, click Switch1 to begin sampling.  Figure 7 shows the graph in action. A potentiometer was connected to AN0 on our ADR112 and varied to produce the graph. A handy  feature of TestPoint graphs is the inspect button. A click on this button and a copy of the graph data is captured and displayed in a separate window where the data can be examined or cut and then pasted into any application such as EXCEL or QUATTRO PRO.

xtp5.gif (22164 bytes) Figure 7 : First Run

5. Adding a Bar Graph and Numeric Indicator

The application calls for a bar graph and numeric indicator as supplemental methods of displaying the present data value. Drag a bar indicator barg.gif (992 bytes) and a numeric display numin.gif (1004 bytes) into the application. Drag the two objects from the object list into the action list as shown in figure 8, lines 7 and 8. Drag the RS232 icon into each of the gray boxes on these lines to specify the RS232 port as the source of data for these items. Figure 8 shows the items in the application. TestPoint allows for customization of objects including colors, text size,use of bezels and labels etc.. The objects have been customized by removing the bezel and some label options to keep the application panel small.

xtp66.gif (22173 bytes) Figure 8 : Indicators Added and Customized

6. The High Alarm

The application calls for a high alarm indicator with a user entered setpoint. this requires three additional objects to be loaded into the application. Drag a math object math.gif (990 bytes), a data-entry object indicator.gif (993 bytes), and an LED object ledd.gif (1007 bytes) into the application.

Note: The names of most of  the objects in the object list have been changed to make the programming more intuitive.  For example, RS2321 was changed to ADR112 because that is what is connected to the RS232 port. This was done by simply double-clicking each object and modifying the labels.  TestPoint then changes all references to that object to the new label automatically.

Double-click the math object and you will be prompted to enter a formula. The formula entered for a high alarm is shown in Figure 19 and sets Math1 to be true if false depending on whether the present value is greater or less than the limit entered by the user.

Mathcal.gif (4527 bytes)

Figure 9 : High Alarm Math

The actual alarm function is performed by lines 9 and 10 in Figure 10.  Line 9 is the math function where the variable Math1 is calculated using the present value of the ADR112 and the limit entered by the user, in this case, 2000.   Line 10 sets the status indicator LED to red or green depending on the result of the calculation.

One additional line was added to the action list ( line 12 ) to close the serial port . This is important to allow other windows applications to use the port when the application is terminated.

xtp7.gif (23707 bytes) Figure 10 : Completed Application

7. Conclusions

After working with TestPoint on a few applications it becomes obvious just how easy and intuitive it is to use. Just look at the action list in Figure 10 and imagine  what   the equivalent Visual BASIC or Visual C code would look like to perform the same function. You don't have to be a programmer to use TestPoint but if you are, you will truly appreciate what the TestPoint people have done to make life easy. This application does not exploit many features available in TestPoint, however,   its purpose was to show  how to use TestPoint with ADR interfaces.   Virtually all of the functions of the ADR   interfaces including, analog and digital I/O, counters, PWM's,  and interrupts can be exploited using this software. There are many other powerful functions available in TestPoint  including VBX and OCX functions, and a new internet toolkit allowing data acquisition and control over the web,  making it an outstanding development platform.   TestPoint is our first choice for application development.


Ordering TPlogo.jpg (9158 bytes)

TestPoint is produced and sold by Capital Equipment Corp in Billerica MA. It sells for around $1000US and an educational discount of 15% is available for qualified educational institutions.  The telephone number for orders is 1-800-234-4232 ( U.S. Only ).

CEC
900 Middlesex Tnpk
Billerica, MA 01821
(978) 663-2002
(978) 663-2626 (fax)

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