Circuit drawings.

MBC-F circuit drawing In most cases, a picture is worth more than a thousand words. Circuit drawings or schematics in most cases fit in very well with this proverb. On the left, we see such a drawing. In lines and curves, the idea behind an electronic circuit is represented. The lines and curves are placed on the sheet of paper according to strict rules, which enables engineers and hobbyists to quickly grasp and understand the idea of the circuit, without reading the full manuals and related books.

On the left, we see the Memory Bank Controller that I designed for my gameboy project. The drawing explains which signals are needed and in what order or timing they are needed.
The rectangular shapes are ready built integrated circuits, in this case a 74HC259 addressable latch.
The curved shapes are logical gates that act upon an OR or and AND function of the signals on it's inputs. You can learn more about this in some good textbooks, like 'The art of Electronics' by Horowitz and Hill.

If you visit the Gameboy section you will see a lot more drawings. Each explaining a particular section of the machine, or an idea how to change the current working.

This webpage is about how I make my circuit drawings, or schematics. There will certainly be better ways to do it, but this is the way I got used to.

How it's done.

I start out by drawing a circuit in PADS, for DOS, as described in the PADS pages. You can find these in the navigator frame. When I'm done, I select In/Out, Plot, Pen-Plotter and make sure the jobname is not printed and that the drawing is not 'scaled to fit'.
When this is done, I copy the file to a floppy disk and transport the disk to my main internet computer. What then happens is the following:

   bash-2.05$ mcopy a:buff* .
   bash-2.05$ fromdos <buffS001.P01 >buffs
   bash-2.05$ hp2xx -m png -f buffers.png -d 60 buffs

   hp2xx is free software and you are welcome to distribute copies of it
     under certain conditions. There is absolutely no warranty for hp2xx!
   For full details, read file COPYING (shipped along with this package),
     or write to:          Free Software Foundation, Inc.
                           675 Mass Ave, Cambridge, MA 02139, USA

   HP2xx:  A HPGL converter (xx = mf, eps, pcl, pcx, img ...)
           V 3.4.4  (03/06/22)   (c) 1991 - 1994 (V3.20) Heinz W. Werntges
                                 (c) 1999 - 2003 Martin Kroeker

   Reading HPGL file
   Writing Cmd: 1 2 5 10 20 50 100 200 500 1k 2k Page number 1 of range 0 - 0
 
   HPGL commands read: 3714
   HPGL command(s) ignored: 0
   Unexpected event(s):  0
   Internal command(s):  3706
   Pens used: 1
   Max. number of pages: 1

   Width  x  height: 151.50 x 200.00 mm, width adapted
   Coordinate range: (4, 4) ... (2622, 3460)

   Plotting in buffer

   Processing Cmd: 1 2 5 10 20 50 100 200 500 1k 2k
   Writing PNG output: buffers.png
   ................................................
   bash-2.05$ mv buffers.png ~/internet/fruttenboel/Gameboy/
   bash-2.05$
   
I first copy the files to a scratch directory with mcopy. Then I convert the files from DOS format (CR/LF) to Unix format (only LF) with the fromdos command.

When this is done, the HPGL file can be converted into a PNG file with the hp2xx command. In this particular case, the command was:
   hp2xx -m png -f buffers.png -d 60 buffs
   
The options are prefixed with a dash. Their meaning is as follows:
   -m    format to print in. In this case use the PNG format
   -f    output the graphic data to the file following this key
   -d    specifies the DPI number; in this case, 60 DPI was used
   -w    specify the width of the graph, in mm
   -h    specify the height of the graph, in mm
   
In most cases you need to fiddle a bit with the -d parameter. It's more efficient than trying to change the size of the picture with the -w or -h parameters.

When done, I copy the graphic files to the right subdirectory on disk and I try to load it into the webpage. When it all works as expected, I upload the files from my local machine to the webhost.

Page created January 2006,