Screen Printer Interface (Version 2.0) From Macrotronics
David D Thornburg
Los Altos, CA
More than anything else, I use my Atari computer for the creation of pictures. For various reasons, it is not enough for me to see these pictures on a TV screen — I also need copies of them on plain paper. Fortunately, there is an exceptionally well designed product which makes this a very simple task. That product is the screen printer Interface from Macrotronics. This program allows the user to transfer any image from the display screen to a suitable graphics printer with a single keystroke. The printed image can (if you choose) preserve grey scales, and can be printed in any size from a single sheet to a poster which would cover a wall. The user can choose among several printers (Trendcom, IDS, Centronics, Epson), and does not need the Atari 850 interface unit. Instead of the 850, Macrotronics provides a printer interface cable which connects to joystick ports 3 and 4. The screen printer software comes on a disk containing DOS 1, and they also provide a copy of the utility which is compatible with DOS 2.
The manual is clearly written and contains many examples showing the use of this interface with all language environments presently supported by Atari (BASIC, Assembler, PILOT).
Setting It Up
To use the system, one first connects the printer to the joystick ports with the cable provided and then boots the system from the disk supplied. During the boot process, the screen prompts the user for information on the printer being used. Once this is done, the rest of the program is loaded (the total utility occupies less than 3K bytes) and the familiar blue screen appears.
From this point on, the printer driver software is tucked safely inside the computer where it remains to do your bidding until the computer is turned off. Any command which sends information to device P: will cause this information to be printed. BASIC commands such as LPRINT behave just as they would for an Atari printer connected through the serial port.
While this system supports all text printing functions, the real value of this interface package is the power it gives as a graphics printing tool. Any time this system is in the computer you can get a dot-by-dot copy of the screen image by simply typing CTRL-P. Macrotronics has created some default printer conditions which cause most images to be printed quite nicely. The user has total control over the system parameters and can change the settings of various registers to create many different effects.
For example, the printed image can be scaled independently in both axes by POKEing a number between 1 and 16 in each of two memory locations. The default scale (16) produces a figure which fits nicely on 8.5" wide paper. As the scale values are decreased, the image size increases by 16/n where n is the scale value. Wide images are printed in multiple strips which can then be glued together. On multiple strip printouts, each strip overlaps the previous one by a little bit to make strip alignment simple. This attention to making life simple for the user is beautiful!
In addition to using the scale variables to make large pictures, they can also be used to adjust for the fact that most dot matrix printers have different inter-dot spacings on each axis. To get an accurate square on the Epson MX-100, for example, the vertical scale should be set to 14 (with the horizontal scale left at 16). The result is almost perfect.
In addition to scaling, the user can select positive or negative images, grey scale or black and white, determine grey scale from either hue or luminance data, print data which has been "fine scrolled," and print players and missiles.
In short, if your Atari computer can generate it, the Macrotronics screen printer can print it.
I use this software almost every day. So far I have used it to print the illustrations for three book manuscripts, numerous articles, several large posters and some custom bumper stickers.
The Only Error
The only error I have uncovered is that the default grey scale setting uses hue data rather than luminance data, but this is just a documentation error — the software works perfectly.
To see more examples of printouts made with this utility, look at any "Friends of the Turtle" colume in COMPUTE!, or at the book Picture This!, soon to be published by Addison Wesley.Figure 1.