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<TITLE>RE: [sdiy] mcu project with too few I/O lines :(</TITLE>
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<P><FONT SIZE=2>Use 74HCT595's if you're short on outputs. Use 74HCT165's if you're short on inputs.</FONT>
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<P><FONT SIZE=2>John Speth</FONT>
<BR><FONT SIZE=2>Coherent Molectron</FONT>
<BR><FONT SIZE=2><A HREF="mailto:john.speth@coherentinc.com">mailto:john.speth@coherentinc.com</A></FONT>
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<P><FONT SIZE=2>> -----Original Message-----</FONT>
<BR><FONT SIZE=2>> From: Bert Schiettecatte </FONT>
<BR><FONT SIZE=2>> [<A HREF="mailto:bert.schiettecatte@esat.kuleuven.ac.be">mailto:bert.schiettecatte@esat.kuleuven.ac.be</A>]</FONT>
<BR><FONT SIZE=2>> Sent: Friday, May 23, 2003 11:24 AM</FONT>
<BR><FONT SIZE=2>> To: synth-diy@dropmix.xs4all.nl</FONT>
<BR><FONT SIZE=2>> Subject: [sdiy] mcu project with too few I/O lines :(</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> hi all,</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> i'm doing a microcontroller project here with an optrex graphical </FONT>
<BR><FONT SIZE=2>> display (128x64), rotary encoder, led matrix (16 leds), and key </FONT>
<BR><FONT SIZE=2>> matrix (16 keys). of course there is also the midi and in system </FONT>
<BR><FONT SIZE=2>> programming connectors. unfortunately my microcontroller (atmega8) </FONT>
<BR><FONT SIZE=2>> does not have a lot of i/o lines available, and I'm left clueless </FONT>
<BR><FONT SIZE=2>> how to interface all that stuff to it. The display has an 8bit </FONT>
<BR><FONT SIZE=2>> data bus + a few i/o lines for reading, writing, etc. for the </FONT>
<BR><FONT SIZE=2>> led matrix, i'd like brightness control for each led (PWM?). </FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> I thought about using a key encoder and maybe an LED driver but </FONT>
<BR><FONT SIZE=2>> those ICs are pretty expensive (7$ for a key encoder, that's more </FONT>
<BR><FONT SIZE=2>> than a microcontroller!). does anyone have some advice here and </FONT>
<BR><FONT SIZE=2>> how to interface this stuff without buying tons of additional ICs </FONT>
<BR><FONT SIZE=2>> which cost a lot of $$$?</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> thanks,</FONT>
<BR><FONT SIZE=2>> bert</FONT>
<BR><FONT SIZE=2>> </FONT>
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