OSD

(last updated: 2003/08/17)

Purpose: Use the STV5730 to generate text over composite video.

Overview

The STV5730(A) is an integrated circuit made by ST Micro. Given a composite video signal, and send it commands through its digital 3-wire interface, it outputs the video signal with text overlayed on the video image. It was originally created for VCR and television manufacturers to provide on-screen programming user interfaces. It also has its use in video surveillance systems where each camera image is overlayed with text describing its location, date, time, etc.

This project makes use of the DT108 board from Dontronics. Only the electronic components with the STV5730 are mounted on the board. The controller interface will be through the avr_io. The avr_io acts as RS232-to-I/O interface. A Java application, called “osd_test” will send commands to avr_io to set/clear outputs on the avr_io’s AVR microcontroller. So the serial interface to the STV5730 is actually driven by the osd_test Java application.

The system is presented in the following diagram:

The osd_test Java application simply causes “12345” and “6789A” to appear on the video image. This project is only used to work out the interface to the STV5730. It does not use the osd chip to display anything useful. There is no user interface for the osd_test program. Since the avr_io is used as the interface, it takes a while (about 1 minute) before the desired output appears.

Specifications

1. Uses the avr_io

2. Uses the STV5730 on-screen-display integrated circuit.

3. Overlays text onto a composite video image – displays “12345” and “6789A” on the next line.

4. A Java application drives the serial interface to the STV5730.

My Setup:

- PC running JBuilder6

- STK200 development board with the AT90S8515 running the avr_io firmware

- DT108 board from Dontronics with only the STV5730 circuitry installed

Modifications:

1. 6x1 header installed at pins 15-20 of the Atmel uC.

2. Wire installed from pin 10 to pin 19 of the Atmel uC (ground).

3. Cut trace between R7+R8 to Q2. Bridge the gap with a 100 ohm SMD resistor.

4. R7=6.8K, R8=3.3K

5. Y2 = 14.31818MHz

6. C10-C11=20pF

7. R9=68, R10=1K

8. Video out and Video in attached by wire to two panel mount RCA jacks

Download (see Attachments)

osd.jpg - picture of setup

osd_board_install.gif - DT108 with components installed

osd_connection_diagram.gif - connection diagram to the avr_io

osd_test - osd_test java project (Jbuilder6)

Notes:

1. Reference: "Get Hooked on Video with the STV5730A", Fred Eady; Circuit Cellar Ink, March 2003

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