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Rildo Pragana: Running a GDI printer under Linux -- part 6 - Writing the printer software

Sep 03, 2000, 13:56 (0 Talkback[s])
(Other stories by Rildo Pragana)

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"In this final article of the series I will look at some details when writing the actual printer software. The main idea, as I said before, is to simulate the nearest possible the original working driver (under the other OS), so you will not have to think too much with command details nor discover the meaning of all registers inside the printer interface. If it works for the other, it will work for Linux as well. Of course, there will be found problems with timings, required commands (most are garbage, as you will discover, which explains why my Linux driver is twice as faster), and some minimum parameters to setup a correct printing image. The easiest way to get the parameters is printing with several page sizes but the same material (say, a image in MS-paintbrush) and noticing what changed between the captured data for both cases."

"The pulses timings are more difficult to get. You will have to experiment with them, placing delays with usleep() or even sleep(). Get first the log generated by Bochs, calling the function bx_printf() at the devices.cc source file to get the timings in machine clocks and convert them to microsecond units. I have rewritten several times my Linux driver to get the best fit."

"This article will be a tour through my printer driver's implementation, so you get a feeling of what to do after starting discovering your printer. As I have done myself, you can start to code your driver even before everything is well understood, if you follow the mimic principle. Much functionality of my printer was discovered that way, as my first driver was very crude to be useful. I dare you to write a working driver, even if it only write a tiny line, like my first experiment. Go ahead! Make your printer sing!"

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