5. X-Y Plotter (Feb 1993)
 

Hardware: DIY ISA bus interface logic

Software: MS MASM Macro Assembler for the Intel 8086 family

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One of the first projects I built was an X-Y plotter for a programmer friend who wanted to learn about stepper motors.
 

I made this when the IBM PC-XT was the current model of personal computer, and I coded it in MS MASM - Macro Assembler for the Intel 8086 family. I would have preferred an interrupt driven system, but it was difficult even then to work out how to do this without interfering with other drivers, so for expediency I wrote it using a software based timer. I built the interface hardware on a dedicated IBM-PC ISA prototype pcb.

 

I used a carriageway stripped from an old printer as the X-Y platform and added a couple of stepper motors along with optical sensors to detect end of carriage and end of paper.

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As the software evolved I added a paper feed function and utilised the basic font located in the BIOS of every PC. I also made it print character dot rows in both directions to halve the time.

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