
low), you might need to either change your UART
configuration in software or “flip” the circuit so
the LED’s cathode is connected to GND and the
high side of R2 (currently connected to VCC) is
connected instead to the I/O pin. The goal here
is to have the LED be solid on when data is not
being transmitted and then blinking rapidly
when bits are being sent.
You can download the complete Arduino code
from my site at grandideastudio.com/opticspy,
under Demonstrations; a snippet is shown in
Figure
C
. You’ll also find example code for the
Parallax Propeller multicore microcontroller
(parallax.com/propeller-1), the tiny Tomu board
that fits insid