[LAU] Roland A500S: snd-usb-audio error -5

Ralf Mardorf ralf.mardorf at alice-dsl.net
Sun Jan 29 08:14:07 UTC 2017

On Sat, 28 Jan 2017 17:55:40 -1000, david wrote:
>So I wonder. Is there some sort of upper speed limit in the MIDI 
>standard? Is the MIDI standard smart enough to negotiate speeds if 
>various MIDI devices differ? Or was the MIDI standard strict in saying 
>that your device must operate at this official speed?

You are aware that MIDI data simply is send and received without a time
stamp and without any sync. The software checks if an ACIA/UART
register reports that a byte was received by a short machine language
endless loop. The endless loop is only interrupted by a branch, if a
byte was received, to read the byte and then to continue the endless
loop. On old computers such as the C64 a lot of MIDI operations were
done by even disabling IRQs. The 65xx chips have a command to disable
timer and break command/flag IRQs, named SEI. One MIDI interface must
use the same rate on both ends, the receiver and transmitter, but if
you use different interfaces you could ignore the MIDI standard and
chose any other rate, as long as sender and receiver chose the same
rate. IOW one interface could not communicate with several MIDI
interfaces using different rates.

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