17 Feb
2015
17 Feb
'15
9:07 a.m.
Hanspeter Portner wrote:
While MIDI over DIN is asynchronous, USB bulk transfers have an implicit
throttling mechanism, i.e., a packet transfer is not complete until the
device has chosen to accept it. This means that the bandwidth is just
as high as the device can process the data. USB/MIDI interfaces cannot
run faster than DIN cable speed, and there might be devices where the
USB interface has been duct-taped onto an existing MIDI interface. (And
the really stupid MFM0860 chip is _slower_ than 3125 bytes/s.)
Regards,
Clemens
On 16.02.2015 18:36, Harry van Haaren wrote:
USB MIDI must use bulk transfers, which are not allowed for low-speed
devices.
No, the MIDI "cable" baud rate is
31250, while MIDI over USB runs
at 112500.
Where do these 112500 Baud come from?
Just curious...
Does this refer to low-speed USB-MIDI (e.g. 1.5Mbit/s)? high-speed USB has a maximal packet size for bulk
transfers of 512
bytes, I'm not sure though whether this applies to USB-MIDI, too?
512 is the _only_ allowed value for the maximum high-speed bulk packet
size, so every high-speed device must be able to handle such packets.
-Bandwidth:
lots better than DIN-cable MIDI, but limited
Depends on underlying USB speed, I guess