DVITester is an automatic test equipment intended for video signal path verification during the post-production Automatic Test Procedure (ATP) in systems featuring DVI or HDMI ports.
DVITester plugs directly into the DVI or HDMI socket on the equipment under test (EUT) and into a USB port on the system running the ATP routine. DVITester analyzes the video frames output to the DVI or HDMI port and signals their validity to the ATP system via the USB. DVITester emulates a standard USB HID keyboard, hence no custom driver is required for ATP equipment running operating systems with native support for USB HID interface.
Examples of Use
Testing functionality of a digital video interface port has never been so easy - ATP software sends test patterns and reads back virtual keyboard's scan codes reporting video frames validity. Visual pass validation is also available (LED) if no automatic process is required.
Here's an example for a PCI Express video card being tested with DVITester.
In another example a tiny PC system running self-test, examines its own video output with DVITester without intervention of the operator.
DVITester detects numerous problems in digital video signal path. Imagine a system being tested, which provides DVI or HDMI video output out of a native LVDS interface. In such a system, LVDS is first converted to parallel video bus, and then to TMDS. DVITester will verify digital video port functionality in all three subsystems: LVDS, parallel video, DVI/HDMI output.
ATP Software Information
No USB driver is required - the DVITester is recognized as a Plug-N-Play USB keyboard by HID-enabled operating systems. On the first valid frame the USB interface will transmit 'p'.
On the first invalid frame it will transmit 'x'. If 'x' received while sending series of only valid frames to the tested equipment means there's a hardware problem in the system under test.
ATP software should enable maximum color resolution up to 24 bpp in order to enable all pixel bits, otherwise pattern recognition will not work.
In DOS 6.22 SEA.EXE program may be used to display test frames. Press * to choose screen native resolution and color depth.
Use sample pattern (for 800x600 resolution) or create your own. Any pattern in which each following pixel in the line is the inversion of the previous one will do.
ATP software should not apply any color correction schemes to the output.
ATP software should set the required video mode.
DVITester consists of three main blocks:
TMDS Deserializer. Converts the TMDS serialized video data received from the DVI or HDMI input, to a 24-bit parallel video data bus which is convenient for further analyzing.
Video Data Analyzer. Analyzes the video data, performs video pattern recognition line after line and changes the "VALID" output on frame-by-frame basis according to predefined criteria.
USB Keyboard Emulator. Reports frame validity to the production test equipment.
Valid Test Patterns
The video frame will be accepted by DVITester as valid if each line in it consists of alternating pixels, when each following pixel in 24-bit representation is an inversion of the preceding one. For example, the frame consisting of the pixels 000000 and FFFFFF arranged in a checkerboard pattern, will be accepted as valid one. Click here to download the example of this pattern for 800x600 output resolution.
There are endless variances of possible valid frames - in each frame lines may differ one from another, the important thing is alternating inverted pixels in each line.
DVITester issues a PASS ('p' character from the emulated USB keyboard) or FAIL ('x' character) output each time the series of valid frames are intercepted with an invalid frame or vise versa. The character is transmitted only once after the first valid or invalid frame in the series. The character will not be repeated after consecutive frames while there is no change in frame validity.
1. DVITester PCB
2. USB A-type to Mini-USB cable
3. Video signal cable (HDMI-to-HDMI)