[minima] Re: PTT Schematic
- From: "Steve VK2SJA" <vk2sja@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Tue, 21 Jan 2014 22:20:15 +1100
> we were running out of pins. we should have had a separate PTT input and
> another T/R line as an output. But I had to make do with a single line.
I was thinking about this. The limited number of I/O lines on
micro-controllers in general. I was sure that I had seen a way to
multiplex switches onto the same data lines used for the LCD display data.
It's taken ages to find an example. Which was frustrating because I kept
seeing mention that the standard Audrino LCD library is carefully written
to support just this sort of functionality.
Anyway for the cost of 8 extra resistors it appears that you can have 4
additional switched inputs (push buttons perhaps).
This App Note is for a Basic Stamp micro but I'm reasonably confident the
concept is valid for the Audrino. Circuit diagram and description in the
App Note.
http://www.parallax.com/sites/default/files/downloads/BS1-IC-BASIC_Stamp_1_AppNotes.pdf
Anyway, I think this is one way you might be able to add another 4 input
lines for not a lot of complexity if you ever needed them for anything.
73, Steve
VK2SJA
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