with parts in them that never come out. In my case, many
of these are in the form of Propeller Activity boards
(PABs). My friends at Parallax have introduced a new
product that lets me keep my circuit and free up my
Activity boards. It's called the Circuit Overlay Board
(Figure 6), and it’s compatible with the Activity board and
the various "Boards of Education" from Parallax. Plus, it's
less than six dollars!
You can see the overlay board in action in Figure 7.
On the left is an Activity board with the Charliplexing
circuit installed. On the right is another with the same
circuit soldered into an overlay PCB (printed circuit board).
Like any shield, I can pop this in and out at my leisure —
the PAB breadboard is no longer locked up with a favorite
circuit.
To make matters even better, Parallax has released the
Dip Trace design files for the overlay PCB. The release of
these files will facilitate — and I hope encourage — the
creation of shields for the Propeller Activity board. I've
certainly got plans. Will you join me?
Timer Update
Every day, I seem to find another use for my timer
object (covered in the June 2015 issue) and find reasons
to add features. A note from a Nuts & Volts subscriber
reminded me: Let others review your code — especially the
code you're really in love with. And, no, I'm not ashamed
to say that I'm in love with some of my code. Real men
admit such things.
A gentleman named Dennis Page kindly pointed out
that the mark() method was unnecessarily recalculating
values; these calculations take time, hence affect the
speed of the method. He was absolutely right. I had been
so close to the code that I looked right past this
inefficiency. Thank you, Dennis, for pointing this out. The
updated object is used by the Charlieplexing demos, so
do save it to your Library folder.
Until next time, keep spinning and winning with the
Propeller! NV
August 2015 19
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