Thread: MK14 and MIDI
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Old 29th Sep 2022, 7:49 pm   #27
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: MK14 and MIDI

I rushed home to try this and was immediately sidetracked by a lawn which '...needed mowing'. (It looked fine to me).

Anyway, I eventually loaded up first arpc.hex and sheba.hex (the ones with the output routine modified to invert the MIDI data stream) and put it through the modified output interface which now drives the MIDI instrument's input optocoupler LED on when SOUT = HIGH.

And... it works, just like that. No grumbles from the synth now, it just happily plays the two test tracks.

I did wonder whether the unconnected SIN pin would return a high or a low (ie, whether it was really necessary to tie SIN low, and yes it was - it doesn't work unless SIN is physically tied to 0V (which was to be expected).

Attached, a rough sketch of the output interface I am using. Note that the buffers are probably not even needed, SOUT could probably go straight to the 4K7 base resistor. The interface already had one inverting buffer as it was intended to be driven by a UART-level signal (idle high, active low), so to convert it to work with the inverse output from Silvester's new code I just inserted a second inverting buffer.

I'll probably just leave it as it is (if it isn't broken, don't fix it).
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