[sdiy] Microchip PIC 5 x 4 matrix

[Roman]

The diodes shoud be reversed (RBx=0 at switch read then) or 10k should be pull down and not pull up, otherwise you will not detect pressed button.
Let's not get crazy with series diode with LED, most LEDs will be OK even at higher reverse voltage. And you can always go down with supply voltage to be safer.
If you want to drive 5 LEDs in a single row from one RBx pin pulled low, that's about 15mA, and definitely RBx will not be at 0V anymore then, but maybe 0.5V or more. That may result in varying brightness depending how many LEDs are on in a row. 5 transistors will fix that. That is irrelevant of course if you plan to light only one of 20 at a time.
Roman
Dnia 7 października 2015 15:52 Jean-Pierre Desrochers <jpdesroc at oricom.ca> napisał(a):
I'm about to build a MIDI foot controller
using around 20 normally open footswitches
with there respective state LEDs.
I have a bunch of PIC16F88 micros and want
to use one for this project using as less pins as possible.
(9 pins for the matrix)
I figured out a way to read and feed all switches
and LEDs this way:
http://www.arcenson.com/public/PIC16F88_5x4_matrix.JPG
All the switches and LEDs will be processed one after each other
in an endless loop..
RB5 will send the MIDI data.
Does anybody see something I forgot in that drawing ?
I'm not home and will try it tonight.
Thanks. JP
_______________________________________________
Synth-diy mailing list
Synth-diy at dropmix.xs4all.nl
http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20151007/ee07c603/attachment.htm>