possible to send about 10,000 points to the screen within
the 20 ms target refresh interval. When more than 10K
points are present in the display list, the software driver
will automatically extend the refresh interval as needed so
all points can be displayed. Depending on the phosphor
decay characteristics of your oscilloscope screen and your
personal POV sensitivity, you will probably notice the
onset of image flicker when plotting more than about
12,000 points.
Circuit
Details and
Theory of
Operation
The AGI
schematic is
shown shortly in
Figures 7-9. I’ve
included many
test points (TPxx)
in the design to
facilitate testing
and
troubleshooting.
POWER
SUPPLY — Any
wall wart that can
supply 12-15 VDC
at . 5 amps can be
used to power the
AGI circuitry. As
shown in Figure 5,
regulators provide clean low-noise regulated + 9.75V and
+ 5.0V outputs to power both the AGI analog circuits
( 9.75V) as well as the logic and Arduino Due CPU ( 5.0V).
Construction Note: Both voltage regulators U1 and
U2 get warm and must be mounted to heatsinks. The two
devices must use insulating hardware if they share a
common heatsink or if either heatsink is grounded. Use
large heatsinks to dissipate more heat if driving the AGI
power input with more than about 12 VDC.
26 February 2018
FIGURE 6. Analog
section of AGI
FIGURE 7. Timing and logic.
