Graphical display terminals using large screen cathode ray tubes (CRT) soon evolved. These displays were essentially “up-sized oscilloscopes” whose X-Y beam
deflection was driven by a computer.
Figure 1 shows a specialized XY CRT terminal
that was part of SAGE (Semi-Automatic Ground
Environment): an early air defense system deployed
in the US. By the late ‘70s, Tektronix, Hewlett-Packard, and others sold general-purpose XY
graphics terminals able to show graphs, charts, and
line drawings of all types.
While a far cry from what we take for granted
today, these were important stepping-stones in the
evolution of computer graphics and display
Arduino Graphics Interface
As an undergrad electrical engineering student
some eons ago, I worked on a MODCOMP (Modular
Computer Systems, Inc.) 16-bit minicomputer that featured
a large 19” Hewlett-Packard XY graphics display screen. A
few months ago, I began to wonder: Would it be possible
to replace those half dozen racks of circa 1975
minicomputer hardware with one of today’s $50 credit-card sized computers?
The answer proved to be YES! What resulted, I call the
Arduino Graphics Interface, or AGI for short. With AGI,
you can transform a leftover analog oscilloscope into a
high resolution computer graphics display and gain
valuable insights into computer graphics, digital-to-analog
conversion (ADC), and advanced Direct Memory Access
(DMA) hardware and software techniques. It’s easy to add
a real time clock (RTC) module and interactive controls to
turn the AGI platform into a “CRT CLOCK” (Figure 2) or
other high resolution computer graphics display device.
In this article, we’ll focus on the overall concepts,
circuit design, and hardware fabrication. In Part 2, we’ll
integrate the hardware to XYscope: the software control
and plotting library that enables an Arduino Due CPU +
analog oscilloscope to become a high resolution XY
graphics display. Let’s get started!
AGI Block Diagram & Operational
The block diagram of the AGI is shown in Figure 3.
Turning an Arduino Due into a Vector Graphics Display
Part 1: Design Concepts and Hardware Fabrication
By Ed Andrews WA9UQN
22 February 2018
FIGURE 1. SAGE air defense system used an XY interactive
The early days of electronic computers used teletype machines and line
printers, and later, alphanumeric screens and keyboards as their primary
input-output devices. As computer usage grew beyond census and
accounting applications, the need for improved graphical displays and
output devices became apparent.