Sat Sep 17, 2016 7:49 am
Hi everyone,

I’ve been playing with Matthias’ USB MIDI library (code pulled during Sept), and I’m having a problem:

Although, while using the supplied test program, the MIDI device shows up on my computers (2x Windows 10, 1x Windows 7), no MIDI data is getting through. I’ve tried sniffing the USB traffic and it appears that the UC isn’t sending any packets. But I’m now out of my depth trying to debug this.

USB MIDI library –

I’m using a Maple mini.

Has anyone had a similar experience with this library? Or can anyone suggest how to go about debugging it?

With thanks for your help.

Sat Sep 17, 2016 11:06 am
There is now a branch of the repo that has this option included

If you download this branch, you can select Midi from the menu … addMidiHID

As far as I’m aware midi works (as does HID etc)

If not you could try PM’ing @madias

Sat Sep 17, 2016 11:22 am
Brilliant, thanks, I’ll give that a go!

Sat Sep 17, 2016 11:43 am
I tried that branch and had the same problem.

However, I found that by changing USB_MIDI_RX_EPSIZE and USB_MIDI_TX_EPSIZE to 0x40 instead of 0x74, it started working. I have no idea why this worked, but I’ve tried switching back and forth and it consistently doesn’t work with 0x74 and does with 0x40. The comment on that line of code suggests 0x40 was the original value but it was later changed to 0x74.

Just mentioning in case it helps.

Sat Sep 17, 2016 11:48 am

I’ll PM @madias and see if he had the same problem

Sat Sep 17, 2016 10:16 pm
Hello, it’s a long time ago I played with MIDI and all I know is that I indeed played/experimented with the USB_MIDI_RX_EPSIZE. Maybe I uploaded a “bad” value for this. Sadly I have no MIDI equipment here. One thing could be possible: I created the whole stuff on OSX. Maybe the OSX driver is more “accommodating” with such things. So sorry about that, I didn’t got any response as I uploaded the MIDI stuff and please stay with value 0x40.
Keep in mind, that the sysex isn’t really implemented. I experimented successfully with sysex, but it’s not in this repo (wasn’t really handy to go for public). If you need sysex I can upload it somewhere (github) but the whole folder, because I changed many things.

Sat Sep 17, 2016 11:45 pm
Thanks Matthias

I have an old Casio keyboard which has midi, but I’d need to find the power supply, as its been ages since i used it.

If the change to USB_MIDI_RX_EPSIZE seems to fix a problem, perhaps I should update the code, as it sounds like the midi feature is not used by many people , so this won’t have a big impact

Sun Sep 18, 2016 7:15 am
Thanks Matthias. The project is now working very well for me, so I really appreciate your work on this!


Sun Sep 18, 2016 7:33 am
PS, I’m not using Sysex, so it’s possible that my change has broken that.

Sun Sep 18, 2016 10:01 am
ofnicolson wrote:PS, I’m not using Sysex, so it’s possible that my change has broken that.

Sun Sep 18, 2016 10:44 am
I think the F4 USB code is likely to be different from the F1, but the upper levels of the code are probably interchangable

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