Test Connections
 
All of Geotest's PXI products support a variety of programming environments including ATEasy, C, LabWindows and LabView. This application details how one can use LabVIEW (LV) to control a GX5295 Dynamic Digital Instrument. Additionally, this application shows how to incorporate the LabVIEW VIs with ATEasy’s test executive, providing a complete test program.

The GX5295 has 32 IO channels with each channel having PMU (parametric measurement unit) capabilities. This example uses the PMU functions to perform a Connectivity test on the Device Under Test (DUT). Additional tests (functional and parametric) can be easily added using the basics detailed in this example.

Test Methodology
Tester to DUT connectivity is verified by forcing a small sink current on all DUT pins (this example excludes Vcc and ground), and measuring the resulting voltage drop across the ESD diodes on each pin. The voltage drop should be equal to the voltage drop across the PN junction of the ESD diode – approximately 0.6V to 0.75V. If the DUT is not connected to the tester, then the resulting voltage will be approximately equal to the low commutating voltage (sinking a current) specified for the pin’s PMU. The commutating voltage in this example is set to +5V and -2V.

Device Under Test (DUT)
The DUT is a 20-pin octal latch (Figure 1). The DUT is installed in a 20-pin TSSOP socket, which is mounted to a demonstration board. The board routes all of the GX5295 signals to the DUT socket. In addition to providing the IO interface, the GX5295 is configured to provide Vcc using one of the four auxiliary PMU channels available on the GX5295.

Figure 1:  Device Under Test (DUT) – Octal Latch
Figure 1:  Device Under Test (DUT) – Octal Latch
(ATEasy GUI Interface)


The DUT board also provides three different fault insertions switches; S2 inserts an open to pin 2 (Qout 1), S3 places a short between pin 5 (Qout 2) and pin 6 (Qout 3), and S4 shorts pin 9 (Qout 9) to ground, as depicted in Figure 2 below.  
Figure 2:  DUT Fault Insertion
Figure 2:  DUT Fault Insertion


Using LabVIEW with the GX5295
The following example was created using LV 7.1. A VI was created that accepts three arrays of clusters which define the DUT input pins and signal names, the output pins and signal names, and the Vcc pin (and signal name). Also passed into the array is the GX5295 PXI slot number, and the connectivity pass/fail parameters.

The output of the VI is an array of clusters listing the signal names (which can be correlated to the input cluster arrays in order to find the DUT pin numbers), the measured connectivity voltage for the signal, and a connectivity pass/fail LED indicator. These VI panel and parameters are shown in Figure 3 below.

The connectivity VI wiring diagram is shown in Figure 4a and Figure 4b. While a complete description of the VI’s operation is beyond the scope of this article; in summary, the VI will set the Vcc to 0V, force -0.5mA on each DUT pin, and then measure the resulting voltage on each of the DUT pins. The resulting voltages are then recorded in the output cluster array and compared to the pass/fail parameters which is passed into the VI. The results of the comparison are recorded in the output cluster array.

Results of a good connectivity test are shown in Figure 5 below. Results of a failed connectivity test are shown in Figure 6 below after setting the S2 and S4 fault switches.

Figure 3:  LabVIEW Panel for testing DUT connectivity
Figure 3:  LabVIEW Panel for testing DUT connectivity

Figure 4a:  Connectivity VI Wiring Diagram
Figure 4a:  Connectivity VI Wiring Diagram

Figure 4b:  Connectivity VI Wiring Diagram
Figure 4b:  Connectivity VI Wiring Diagram (cont'd)

Figure 5:  Connectivity Test Passed
Figure 5:  Connectivity Test Passed

Figure 6:  Connectivity Test Failed (failures injected)
Figure 6:  Connectivity Test Failed (failures injected)


Using LabVIEW with ATEasy
Control and test execution of this application can be done via the GX5295’s ATEasy driver or via the LabVIEW VIs as shown above. Figure 7 shows how the GX5295 can be controlled using its ATEasy driver.

Figure 7:  Using the ATEasy Test Executive to control the GX5295 Connectivity test
Figure 7:  Using the ATEasy Test Executive to control
the GX5295 Connectivity test

To manage test execution using the LabVIEW VIs, the working VIs can be imported into ATEasy using the LabVIEW VI Import utility which is part of ATEasy's tools package (Figure 8). A VI call from within ATEasy can be configured so that the LV panel is hidden, or made visible.  Figures 9, 10 and 11 show ATEasy's test log output as a result of running the LabVIEW Connectivity VI with the panel hidden (Figure 9) and with the panel visible (Figure 10 and Figure 11). ATEasy's test log also shows a "Passed" connectivity test (Figures 9 and 10), and a "Failed" connectivity test (Figure 11). In each instance, the measured values and the pass/fail indicators can be correlated between the LabVIEW VI, and ATEasy’s test log output. Expanding this application to include DC parametric and functional tests is simply a matter of importing additional LabVIEW VIs into ATEasy that support these tests.

Figure 8:  ATEasy LabVIEW VI Import Utility
Figure 8:  ATEasy LabVIEW VI Import Utility

Figure 9:  ATEasy Output of LabVIEW Connectivity VI
Figure 9:  ATEasy Output of LabVIEW Connectivity VI –
LabVIEW Panel is hidden

Figure 10:  ATEasy Output of LabVIEW Connectivity VI
Figure 10:  ATEasy Output of LabVIEW Connectivity VI –
LabVIEW Panel is displayed

Figure 11:  ATEasy Output of LabVIEW Connectivity VI
Figure 11:  ATEasy Output of LabVIEW Connectivity VI, Failed Condition

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