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1  Forum 2005-2010 (read only) / Interfacing / Re: works: MIDI-IN: code + schematics on: November 01, 2010, 06:01:13 am
Yep, I did try your schematic, no luck.  My experience was the same as Charbot.  

For those planning on building this, order a few of both optocouplers to be safe. smiley-wink

2  Forum 2005-2010 (read only) / Interfacing / Re: works: MIDI-IN: code + schematics on: October 30, 2010, 09:21:09 pm
Also the 4N28 optocoupler did not work in any configuration for me.  I could verify the chip itself was working fine using the test circuit on this page [1] and I verified the Arduino Rx worked fine and MIDI signal was fine.  I did finally get things working with the CNY17-4 optocoupler though.

Here is the configuration that ended up working for me:
Arduino Duemilanove connected to Macbook USB
M-Audio Keystation 61es
Schematic in the original post of this thread, substituting CNY17-4 for 4N28

Really strange about the 4N28. No idea why it would not work in this configuration other than some sort of variation between manufacturers [2].

[1]
Test Circuit, see #4:
http://www.technogumbo.com/projects/Learning-to-Use-an-Optocoupler-or-OptoIsolator/

[2] 4N28 by VISHAY SEMICONDUCTOR. I bought mine here:
http://www.newark.com/vishay-semiconductor/4n28/optocoupler/dp/88K1389
3  Forum 2005-2010 (read only) / Interfacing / Re: works: MIDI-IN: code + schematics on: October 30, 2010, 09:20:20 pm
tep:
Quote
From what I understood it is a different voltage level, so that's a bit more than precaution.
(BTW that's why the 3.3k resistor is 1k if a FTDI is connected.)

I know this thread is a little old, but can anyone explain or point me to some literature why the 3.3k resistor looks like 1k when powered up and how the FTDI relates?
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