A SSTV Test generator
Table of contents
After finishing my
DDS Module with the Analog Devices AD9835
I want to test it. Because I am very interested in electronic imaging
I decided to try it with SSTV. The folowing SSTV testgenerator creates
a color bar picture using the Martin-1 SSTV mode. It also sends the
correct VIS code before sending the test pattern.
THIS CONTENT IS PROVIDED TO INTERESTED PEOPLE "AS IS" FOR NON COMERCIAL
PURPOSE ONLY. UNDER NO CIRCUMSTANCES I AM RESPONSIBLE FOR ANY DAMAGES
TO YOUR RADIO, PC OR OTHER EQUIPMENT. THIS DEVICE WAS TESTED UNDER
DIFFERENT CONDITIONS AND UNTIL NOW IT WORKS WITHOUT PROBLEMS.
This is the schematic of the testgenerator. It is based on a PIC 16F84
from Microchip running at only 4 MHz. 20 MHz would give much better
control over timing critical functions but even with 4 MHz the timing
of the testgenerator is accurate enough to produce a good quality
testing picture. When you press the switch S1 the testpattern is sent.
After sending the generator waits for the next key press.
Image 1: SSTV Testgenerator schematic
There is no PCB available for this project. As you can see on the pictures
below the whole testgenerator was prototyped using my
AD9835 DDS Module and my PIC Prototyping Board
on a Breadboard.
These are the PIC 16F84 assembler listings for the testgenerator. They are
in Microchip MPASM (MPLAB) format. Just copy them into a directory,
compile sstv.asm and program the resulting sstv.hex file into the PIC.
Tools.h, Tools.asm - general tools
AD9835.h, AD9835.asm - AD9835 routines
SSTV.asm - main routines of the testgenerator
Or download all of these in this zip file.
To handle ZIP file look at WinZip
Pictures of the finished testgenerator
Here you can see how the module looks during different stages of the building
process and how it looks when it's finished. A picture says more than
Image 2: SSTV Testgenerator
Image 3: Testpattern shown with MMSSTV
Notes & Comments
There is lot of room for improvements in this project. You can for example
add the display of your callsign in the testpattern etc. Feel free to
experiment with the soft- and hardware of the testgenerator. If you add some
new things to it it would be nice if you drop me a line so that I can add
a note about you here.