DVI to PAR digital video interface with LCD

Posted on Sep 3, 2012

This page describes a cheap and simple yet flexible HDMI to parallel 3.3v interface. This allows to connect most LCDs frames to the beagleboard without any further interface required. I am using this myself with some 7inch 800x480 displays which i am using to run Angstrom Linux as well as the maemo on beagleboard project. I have used these lately for some work on Meego. The hardware is rather simple and doesn't consist of much more than the TFP101A panel link receiver from TI. This chip directly outputs 3.3V signals. The dvi2par routes these signals though 22R resistor arrays to reduce reflections. The resulting signals can be fed directly into a LCD screen as depicted below.

DVI to PAR digital video interface with LCD
Click here to download the full size of the above Circuit.

From the day i received my beagleboard rev. B7 i was missing an easy way to use the digital video interface with a small LCD screen. Many people seem to have the same problem and often end up with big and expensive adaptors. Further indication that this is a common problem comes from the fact that the latest incarnation of the beagleboard includes a way to directly interface to the OMAPs parallel video interface. Unfortunatately this only provides 1.8v signals and still needs a converter to interface to the 3.3v signals most raw LCD use. The main components is the TFP101A. I got mine as a free sample from TI. Also visible in this picture is the fact that only the upper 6 of the 8 color bits available on the dvi2par are being used. It's important to make sure that the upper bits are being used if the display supports less than 24 bit color depth. Also visible in the image is the fact that a tiny wire goes from pin 8 of the TFP101A to some other parts on the board is mounted on. Pin 8 carries the SCDT signal which indicates that a valid signal has been detected in the input. In this example the signal is routed to the backlight inverter and makes sure that the backlight is only switched on if a valid HDMI signal is being received. EDID/DDC support The dvi2par also includes an optional i2c eeprom which is meant to allow to use the dvi2par on hosts other than the beagleboard which support to use a displays ddc/edid...

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