I
built the user interface with digital I/O pins and
pull-up resistors. The inputs consist of a recording
switch (active high) and a recording stop switch (active
low). I chose these levels to mimic the bucking dummy’s
circuitry.
Three
LEDs indicate how the Bucky-meter’s software is operating.
One LED flashes when the device is recording. The
two remaining LEDs flash in time with the serial data
loop and the logging loop. The loop LEDs are easily
reassigned to perform debugging tasks. An optoisolator
is provided so that the Buckymeter can replace the
timer board in the bucking dummy. The bull owner I
work with rarely uses the internal timing mechanism,
so I left this feature open for future expansion (see
Figure 2).
|
(Click
here to enlarge)
|
Figure
2—I converted the MCB2130 evaluation board for
the Buckymeter. A few hardware modifications were
required. |
The
serial interface is used to display debugging and
operational data to a Palm Pilot running a terminal
program (or any dumb terminal device). One of the
LPC2138’s UARTs is connected to an RS-232 driver chip
that kicks the 3-V system power supply up to the ±12
V required for RS-232 operation.
