Gemini Industries Printer user manual Example Graphics Program

Gemini User’s Manual

You computer aficionados may have already figured out that the high-order bit of the character controls the top pin, the next bit controls the number-two pin, etc.

Okay, now that you know how to fire the pins, what code do you think will fire pins no. 5,6, and 8 with an 8-bit interface (per the above chart)? How about CHR$ (8+4+1), or CHR$(13)? That may seem like a good answer, but (in the words of Hamlet) ‘lay, there’s the rub:’

CHR$(13) causes BASIC to automatically insert a line feed, CHR$(lO), behind it. These BASIC programs were written several - years ago, before Gemini came along. Gemini is smart enough to use CHR$(13) for a purpose other than initiating a carriage return;

if only BASIC were as smart.

One solution to the above problem is to design your graphics programs so that they only use pins numbers 1 through 7 for 8-bit computers, and numbers 1 through 6 for 7-bit. Because the bottom- most pin that normally can be used is fired by CHR$(l), all commands for the other usable pins will be even-numbered (whatever their combination of numbers to fire whatever combination of pins). With all the codes even-numbered, there’s no need to concern ourselves about unlucky old CHR!$(13).You might want to think about it for a while. There are other ways around the problem, but the even-number approach works (even if there seems to be something odd about it).

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Example Graphics Program

Now that we’ve learned how to send the graphics controls to Gemini, let’s construct a simple character to test low-resolution printing. This program will show you one approach to creating graphic images. In the next chapter, we’ll consider more advanced techniques.

The first step in generating a sample program is to decide where to position the dots. One way is to start with a pencil and a piece of paper, especially paper with square grids printed on it. We will imagine that one dot will cover one square.

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