"sSTv" -- Color SSTV for the Atari ST --------------------------------------- Free demo version 0.9, October 1989. * * * Copyright 1989 by John W. Langner * * * Permission is granted to freely copy and distribute THIS VERSION (0.9) in its complete original form. Features (full version 1.1) -------- * Send and receive the most popular formats: Robot: 8 second black & white. 12, 24, 36 second color. Wraase SC-1: 24, 48, 96 second color. AVT: 90 second color. 24 & 94 second color (receive only). Others will be added in a future version. * See pictures as they are received - no post processing. * Screen contains: Two images with 128x120 pixels of 256 colors. Menu of available commands. * Test pattern generation: Checkerboard, color bars, etc. * Image manipulation: Mirror, rotate, zoom, shrink, etc. * Load and save images with various file formats: NEOchrome. Degas. Own format with 256 colors. * Keep ten images in memory for instant access. * Print images with 17 gray levels. * Compatible with TOS 1.4. * Detailed documentation. (The information below is quite condensed and incomplete.) Hardware Requirements --------------------- * Atari 520ST or 1040ST with color monitor. * Epson (or compatible) printer for printing. * Radio interface: Simple two chip interface (homebrew for about $7) connected to RS-232 and printer ports or more elaborate circuit connected to MIDI port (kits available). Screen Layout ------------- The top line is used for messages and sometimes a prompt for input. Next is the menu with a list of the available commands. Below that, the selection line indicates the currently selected monitor and images. Two "TV Monitors" are at the bottom of the screen. The Menu -------- The first column contains the commands to receive, transmit, print, load from disk, save to disk, and quit from the program. The second column contains the available transmission formats. The third column contains various functions to manipulate images. The last column contains commands to generate test patterns. Monitor and Image Selection --------------------------- At any time, one of the monitors is the active or "selected" monitor. Most of the commands use the content of the selected monitor. The left monitor is selected by pressing the left arrow key. The "<--" will be highlighted, with a red background, to indicate the left monitor is selected. Similarly, pressing the right arrow key selects the right monitor and highlights "-->". There are 10 image buffers in memory numbered 0 through 9. One of the numbers above each monitor will be highlighted to indicate which image buffer is being displayed. Pressing the up or down arrow key will select the next higher or lower image buffer. Sending and Receiving --------------------- First select the desired transmission format with one of the number keys on the main keyboard. Press Return to start receive mode. Press it again to terminate receive mode. Function button Fn causes the currently selected image to be transmitted n times. When Shift is pressed at the same time, consecutive images are transmitted once each. Transmission can be terminated by early by pressing any key. Printing -------- Press P to print the currently selected image. Each screen pixel is converted to a 4x4 group of dots on the printer. Each group can have 0 through 16 dots printed so 17 gray levels are available when viewed from a distance. Speaking of viewing from a distance, pictures on the screen look better if you stand back about 6 feet. Printing uses Epson graphics mode 5 which prints 72 dots per inch on an LX-80 printer. Unfortunately the manual does not contain a comparison of features for different models so I don't know if all the other models support this mode. (I can add support for other common types of printers if someone sends me the required information.) Low Cost Interface ------------------ The Atari ST is not equipped with an audio input so a simple interface is required. The schematic is in the file INTERFAC.NEO. Parts list: Prices shown are from a typical mail-order catalog except where a Radio Shack (RS) part number is listed. C1, C2 100 uF electrolytic, 10 V 2 x .19 C3 0.1 uF disc ceramic .15 C4 0.01 uF mylar .11 C5 0.001 uF mylar .06 C6 0.033 uF mylar .11 D1, D2 1N4001 2 x .10 J1 DB-25S connector to modem port .79 P1 DB-25P connector to printer port .75 Q1 2N3904 or similar .12 R1, R2 4.7 k 2 x .06 R3 10 k trim pot .89 R4 22 k .06 U1 NE 565, phase locked loop .99 U2 CD 4013, dual type D flip flop .29 perfboard (RS part 276-150) .99 two 14 pin IC sockets 2 x .39 --------- approx. total 7.00 R3 must be adjusted so the interface produces a square wave of about 1750 Hz with no signal applied. You do not need a frequency counter to make this adjustment. Run SSTV09.PRG and press the "*" key in the upper right corner of the numeric keypad. The program will display the approximate frequency coming from the interface and will tell you if it is too high or too low. No additional hardware is required for transmit. The internal sound generator chip produces the tones. It is possible to transmit by holding a microphone near your computer's monitor though exact placement of the microphone makes a big difference in the quality of the transmitted signal. High Performance Interface -------------------------- The low cost interface provides a very cheap and simple way to enter the exciting world of Slow Scan Television but it only works well with strong signals. Holding a microphone next to a speaker being driven by a square wave isn't an ideal way to transmit the best quality signal. Finally, swapping cables to receive or print is an annoyance. The program also supports another type of interface: +-------------+ +-------+ +------+ | | | | | | audio --> | demodulator | --> | A / D | --> | UART | in | | | conv. | | | +-------------+ +-------+ | | --> | | MIDI +-----------+ | | port | | | | <-- audio <------- | tone | <-------------- | | out | generator | | | +-----------+ +------+ The tone generator produces a crystal controlled phase coherent sine wave and requires no adjustment. The demodulator must be adjusted but no test equipment is required. (See description of the HPITEST program below.) Kits are available from: A & A Engineering 2521 W. LaPalma, Unit K Anaheim, CA 92801 phone (714) 952 2114 Prices listed here are approximate. Send SASE or call for recent prices and ordering information for kit # 168. The optional tuning indicator / signal analyzer (kit # 169) is recommended for best results. $25 PC boards and documentation only. $90 Complete interface kit. (no software) $25 Full version of the software. (For use only with kit version of the interface; it will not work with the low cost interface described above.) The kit version of the interface is slightly different than the schematic in the magazine article mentioned below. The circuit was modified to operate on a single well regulated 12 to 14 volt supply. Most people already have 12 volts available for their transceivers. HPITEST.PRG ----------- This program is provided to help with testing and adjustment of the High Performance Interface. One of the functions acts like an audio sweep generator and a dual trace digital oscilloscope. To use this, the audio input to the demodulator must be connected to the output of the tone generator. The program slowly sweeps the tone across the range of about 1000 to 2500 Hz and plots the demodulator output on the screen. Demo Version Disk Contents -------------------------- SSTV09.PRG The "sSTv" program. SSTV09.TXT This document. ANNOUNCE.TXT Product announcement. INTERFAC.NEO Low cost interface schematic. HPITEST.PRG High Performance Interface test program. DESKTOP.INF Typical desktop configuration. *.STV About a dozen genuine SSTV pictures from 14.230 MHz. (Those ending with _LC were produced with Low Cost Interface.) Conclusion ---------- SSTV can be very expensive but it doesn't have to be if you have an Atari ST. You can get started for about $10 with a homebrewed low cost interface and the free version of the software. With the High Performance Interface you can get quite acceptable results for about 1/10 the cost of a Robot 1200C. For More Information -------------------- Read my article "Color SSTV for the Atari ST." It contains a brief overview of how color SSTV pictures are transmitted, a schematic of the High Performance Interface, and pointers to several other sources of information on SSTV. It is scheduled for the December 1989 and January 1990 issues of 73 Amateur Radio. After publication, you can obtain a reprint of the article by sending $3 to: 73 Amateur Radio Magazine WGE Center Forest Road Hancock, NH 03449 U.S.A. ATTN: Article Reprints. Please don't ask me to send you copies of information readily available from other sources which are in the publishing business. Otherwise, questions and comments are welcome. Be sure to send an SASE when writing. John Langner, WB2OSZ 115 Stedman St. Chelmsford, MA 01824-1823 U.S.A. (508) 256 6907 Trademarks ---------- ATARI, NEOchrome, ST, 520ST, and 1040ST are trademarks or registered trademarks of Atari Corp. AVT might someday be a trademark of Black Belt Systems or AEA but I haven't seen any mention of it yet. Degas is a registered trademark of Batteries Included Inc. Epson and LX-80 are trademarks or registered trademarks of Epson America, Inc. Radio Shack is a registered trademark of of Tandy Corporation. ROBOT is a trademark of Robot Research Inc. 73 is a registered trademark of someone. (A little R in a circle is next to 73 on the cover but I couldn't find a trademark notice inside.)