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Topic: UNO + Olimex Midi Shield (Resolved) (Read 5 times) previous topic - next topic

marco_c

The current on the LED pins will depend on the LED and the resistors you have put in the circuit, so you can calculate based on theory and see if it is close.

The current on D1 should be the MIDI serial interface.
Arduino libraries http://arduinocode.codeplex.com
Parola hardware & library http://parola.codeplex.com

deseipel

D1 = 7.6mA   (probes on D1 and 5v power supply)

The MIDI OUT DIN pins 4,5 = 4.5mA (is as high as it goes).

This is without the led inserted into the MIDI DIN.  I guess my thought is that, according to what I've read, MIDI operates on 5mA to 0mA.  The MIDI OUT spec only shows  220ohm resistors on pins 4,5 respectively.  So where am I losing .5mA or how can I ramp up the mA?  be gentle.

marco_c

The current should drive an optocoupler (effectively a LED), so in my opinion the 0.5mA is not going to make a big difference to how the LED lights up in the coupler.

Have you checked that the opposite (ie, sending 0xff continuous) gives a current that is at least close to 0mA? That couls also be a problem as the LED would stay at lkeast partially lit.

One other thing that may be worth doing is cheking the specs on the Roland cable to see what is expected there. You may have done this already but there is not info on these posts.
Arduino libraries http://arduinocode.codeplex.com
Parola hardware & library http://parola.codeplex.com

deseipel

The LED isn't hooked up to the MIDI OUT.  And also, there's no octocupler on the MIDI out spec.  I have the board set to send MIDI OUT, so its coming from the board, going through my MIDI/USB cable and into my pc. 

There isn't really a lot of info on my MIDI/USB cable from Roland.  I've used a USB analyzer app that monitors incoming data and nothing registers when I send data through the cable.  The cable works fine with other MIDI devices though.  BUT, if the cable needs the 5mA to register start bits, I'd say it's not getting it.  I don't know if other midi devices absolutely need that 5mA to operate or not.


marco_c

Quote
The LED isn't hooked up to the MIDI OUT


If it follows the standard your MIDI OUT is connected to an optocoupler on the MIDI IN side. There should be something in the middle of the cable you have that is MIDI to USB converter. So it is driving that optocoupler.
Arduino libraries http://arduinocode.codeplex.com
Parola hardware & library http://parola.codeplex.com

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