In order to build an automated in-line test system, robust and reliable, and to guarantee the quality of the production of DVB-T set top boxes. The system must be able to download the firmware and test the funcionality of the STB (set top box). In order to achieve a exceptional productivity ratio, we decided to use double-dwell fixtures in two consecutive in-line test stations, as a result creating a 4 DUTs inside the system at the same time.
The platform used is the modular 6tl-32 system from 6tl engineering. We are using two 6tl-32 stations, and every one tests two DUTs at a time thanks to a double-dwell fixture.
We are using TestStand to create the process model and the parallel test of two DUTs in every 6tl-32 station. All instruments that need to perform the test are controlled thanks to LabView.
Description of the DUT
The DUT is a DVB-T set top box have typical features of these types of devices:
RF input, RF output to TV set through IEC-169-2 connectors and SCART connectors for RGB in/ out, audio, etc…for TV sets and VCR. The DUT features USB ports that make it possible to record from the TV.
Test solution description
Our test system will be based on the true modular 6tl-32 system. We will use two 6tl-32 stations in-line to achieve the take time desired by our customer. Thanks to 6tl engineering concept, every station works independently, and are linked through the conveyors with SMEMA extended, the DUTs manage logistics and the Ethernet allows for sharing test data between them. Every 6tl-32 module features a mass interconnect receiver for connecting the fixturing. The control is through an Industrial PC protected by an UPS and a touch panel. In every station there’s room for integrating rack&stuck 19” instruments as well as a power management module. For every station, the DUT location is defined by the fixturing, the conveyor, the lifter and the pusher. All them are real 19” modules integrated in the 6tl-32 station. The fixture has the probes and wiring to connect DUTs to instrumentation. Fixture changeover is a simple operation thanks to the massinterconnect solution implemented in 6tl-32 stations.
Conveyors transport DUTs through the test stations, thanks to the belt, and its width is set automatically during the fixture changeover operation. Depending on the operation status of the system (testing, fixture changeover, stand-by) the lifter will move the fixture to a concrete position. The pusher is the mechanism used to press the DUT and make the probes contact the test points of the DUT. Both modules, pusher and lifter, are servo-driven, and as a result, extremely accurate positioning is achieved. The switching is again based on modules that are directly connected into the massinterconnect receiver. Other functions needed in our test execution are also implemented in this modules, as pneumatic switching or LED analysis (YAV boards from 6tl engineering). YAV modules cover typical functions needed when developing a functional testing system, and are complementary to the supply from NI with modular instrumentation. All the modules from 6tl are CAN bus controlled thanks to a PCI-CAN board from NI installed in the IPCS, and 6tl Phi6 drivers for Lab View. The SW Phi6 package from 6tl, in addition to the dLV drivers for all 6tl modules, each one includes virtual instruments, and an Operator interface (OI) to control the ATE. The OI is programmed in LabView and helps all the operators do their job without programming knowledge. The OI automatically detects the fixture and therefore the test sequence will execute. The operator has to start the cycle, and all information will be displayed in phi6 OI, as the test progress or the number of failed and passed DUTs.
The 6tl-32 station that receives the DUTs from the production line, features a Datamatrix reader that will identify each device arriving. The code read is put in a file that is shared by all 6tl-32 stations. As two test stations are available in the system, although the TestStand sequence could allow for them to get in one by one, the DUTs are getting into the system in pairs. Once the process is ended in the first station, both DUTs will travel to the second one and at the same time, and another pair will arrive to the first station.
Each station executes a part of the whole test for the DUT. The first station is in charge of testing, the current consumption of DUTs, as well as internal voltages, downloads the firmware and tests that it runs properly. The second station, if the DUT has succeed the previous one, tests the detection of USB in the port, it sets the ‘factory mode’ of the DUT by navigating with the remote control (therefore the IR port is tested) and tests the video and audio signal quality. TestStand automatically generates the test results that are stored in the reports.
The audio and video test are based on studying the video synchronism, the RGB signals and the frequency / amplitude of audio signals. The PCI-5153 scope from NI has performed perfectly for this job. It has been easy to start operating with the module. Set up is fast, as well as programming and executing operations. The controller gives the test engineer a choice between lots of immediate measurements over the signal as well as excellent processing performance.
The system guarantees the quality of the product production covering all the test specification. Having 4 DUTs at a time makes it possible for the cycle time to respond accordingly to the needs of the production line. Thanks to their instruments and software applications, NI products creates the appropriate environment for developing a fast and easy application.
Fulgencio Buendía, Test Systems Engineer
Mario Seco, Test Systems Engineer
David Batet, Business Unit Manager