Hanging notes/data corruption on GPIO input with certain MIDI sources #21
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Hi! Which model of Raspberry Pi are you using? |
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Hello, I am using a Pi 4 model B. Pretty much any song I play has the
problem. I think the songs sound the same wrong way in the same places
every time I play them. I have about 3 to 4 inch wires to the midi jack
and to the Pi GPIO pins from my midi breadboard. I don't know if that
matters.
I tried installing Raspian with Munt to see if it was a hardware problem,
but I don't know how to get it to use the GPIO midi in port.
I will follow up with a link to a midi file and a recording of how it
sounds.
Thanks!
Michael
…On Sun, Aug 16, 2020, 6:44 AM Dale Whinham ***@***.***> wrote:
Hi!
Which model of Raspberry Pi are you using?
Is there any chance you can get me a recording of the hanging notes or
tell me a specific song/time to look for so I can try to recreate the
problem?
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Hello,
Here is a midi file and a recording of it. Notice the obvious stuck note
(there are probably others). Right at the end of the recording the note
gets unstuck. It always sounds the same. When I play the midi file with
Windows sound instead of through the mt32-pi, that note is not stuck.
https://www.sendspace.com/file/yzvwc8
Thank you for your help!
Michael
…On Sun, Aug 16, 2020 at 9:24 AM Michael Hart ***@***.***> wrote:
Hello, I am using a Pi 4 model B. Pretty much any song I play has the
problem. I think the songs sound the same wrong way in the same places
every time I play them. I have about 3 to 4 inch wires to the midi jack
and to the Pi GPIO pins from my midi breadboard. I don't know if that
matters.
I tried installing Raspian with Munt to see if it was a hardware problem,
but I don't know how to get it to use the GPIO midi in port.
I will follow up with a link to a midi file and a recording of how it
sounds.
Thanks!
Michael
On Sun, Aug 16, 2020, 6:44 AM Dale Whinham ***@***.***>
wrote:
> Hi!
>
> Which model of Raspberry Pi are you using?
> Is there any chance you can get me a recording of the hanging notes or
> tell me a specific song/time to look for so I can try to recreate the
> problem?
>
> —
> You are receiving this because you authored the thread.
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Thanks for sending me the MIDI. I've just tested playing this song from Windows on I'm guessing there is an electrical issue with the GPIO circuit.
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I'm experiencing something similar with the PI-MIDI board I've just received: the onboard MIDI interface is doing drunk renditions of the MIDI data while USB is fine. Here's some listening material: https://www.dropbox.com/s/5kcjc7rlauv0scf/recordings-mt32pi.zip?dl=0 It's not identical, but there's a slim chance we're both having the same problem. I'm still in the process of ruling out the usual suspects (cables, power adapters, different Pi units). |
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Thank you for your help. It is good to know I may be able to fix it. I
have extra parts and can make a new midi board. I will do more testing and
listen to and try the other person's example that is also having problems.
…On Mon, Aug 17, 2020, 5:26 AM Dale Whinham ***@***.***> wrote:
Thanks for sending me the MIDI.
I've just tested playing this song from Windows on mt32-pi v0.3.1, using
my GPIO midi interface - it worked just fine with no hanging notes.
I'm guessing there is an electrical issue with the GPIO circuit.
- Can you measure the resistors to make sure they're the correct
values and in-spec?
- Do you have another optocoupler you could try?
- Is your PSU and USB power cable good enough for the Pi? If you test
with Raspberry Pi OS/Raspbian, you should not be getting any 'lightning
bolt' symbols on the screen or undervoltage warnings in dmesg if your
PSU is good and the Pi is under stress.
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I listened to Nuey San's file and it seems to be missing notes. I also
think I experienced this at one point. It's possible there is a loose
connection or bad resistor or something. I have a couple of questions:
- Are you both trying on a Raspberry Pi 4?
- Nuey San, when you play the file, does it sound identical every time you
play it, where it always misses the same notes?
Thanks!
…On Mon, Aug 17, 2020 at 8:23 AM Michael Hart ***@***.***> wrote:
Thank you for your help. It is good to know I may be able to fix it. I
have extra parts and can make a new midi board. I will do more testing and
listen to and try the other person's example that is also having problems.
On Mon, Aug 17, 2020, 5:26 AM Dale Whinham ***@***.***>
wrote:
> Thanks for sending me the MIDI.
>
> I've just tested playing this song from Windows on mt32-pi v0.3.1, using
> my GPIO midi interface - it worked just fine with no hanging notes.
>
> I'm guessing there is an electrical issue with the GPIO circuit.
>
> - Can you measure the resistors to make sure they're the correct
> values and in-spec?
> - Do you have another optocoupler you could try?
> - Is your PSU and USB power cable good enough for the Pi? If you test
> with Raspberry Pi OS/Raspbian, you should not be getting any 'lightning
> bolt' symbols on the screen or undervoltage warnings in dmesg if your
> PSU is good and the Pi is under stress.
>
> —
> You are receiving this because you authored the thread.
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Hello, I completely built a new MIDI interface with all new parts and I used a different set of resistors from a different manufacturer and measured each one before soldering it in to get the closest I could to the recommended values (and they were very close), and after everything was in place, I tried it and I still have the exact same problem. I had this problem before and after installing a PCM5122 hat. Are you testing on a Raspberry Pi 4 when you are having no issues? Any further help would be appreciated. |
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I noticed this diagram uses different resistor values (220, 470 and 1K). I am not sure if trying that would help. https://www.instructables.com/id/PiMiDi-A-Raspberry-Pi-Midi-Box-or-How-I-Learned-to/ |
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I'd use that circuit diagram with caution, it has a pull up going to the +5V and the UART on the Pi is only capable of 3.3V, so there is risk of damage. Someone in the comments on that page also noticed this. Sorry you're still having trouble, I'm really not sure what to suggest 😥 Can you provide hi-res photos of your circuit and how it's connected to the Pi? The circuit in the README is the same as on this page: https://www.samplerbox.org/article/midiinwithrpi Was your SD card 100% clean when you installed Can you try to test the interface in a clean install of Raspbian to try and rule out |
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Thanks. It is really late, so I will provide the pictures and work on this more tomorrow. The SD card was clean formatted before installing the MT-32 Pi. I noticed the Diode is different in the link you provided. I am not sure if that makes a difference or not. Also, I have a Pi 3 that I can try it on, but it will take some work to get to it (it's in a NesPi case acting as my Pi-hole). |
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Uh oh - yes, you're absolutely right, it's meant to be a 1N4148. Please try with one of those if you can! |
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I will have to order some. Hopefully that will fix it! Thanks! |
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I hope so! 🤞🤞 If this was the reason, I apologise for the mistake - you're the first person to actually attempt to build the circuit from the schematic listed here and report back. I'll fix the schematic ASAP. |
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@thorr2 to answer your questions: I've tested on a Pi3 and Pi4, the dropped/stuck notes are different for each Pi tested, but they seem consistent for each. |
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Sounds like we have the same problem. I will hopefully have the new diode
tonight. If it fixes it, maybe your pi hat also has the wrong diode. I
will keep you posted.
…On Tue, Aug 18, 2020, 8:14 AM Nuey San Waldman ***@***.***> wrote:
@thorr2 <https://github.com/thorr2> to answer your questions:
I've tested on a Pi3 and Pi4, the dropped/stuck notes are different for
each Pi tested, but they seem consistent.
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I installed the new diode and it did not change anything unfortunately. I guess I will try your suggestion of installing Raspian and trying to make that work. I tried once before but didn't get very far. Hopefully the link you provided will provide all the necessary information. I also have a Pi 3 I can try, so I may try that first. |
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I tried the Pi 3 and it also had the issues, but less so. |
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This is the spec sheet for the 6N138 I used: https://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/6N138-39%20Series.pdf |
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This is interesting (see the answer talking about 5V): https://electronics.stackexchange.com/questions/165255/midi-in-many-circuits |
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Sorry the diode didn't change anything 😢
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Thanks. I soldered in the 0.1 uF capacitor and changed the circuit to wire it up to the 5V on pin 8 with pin 6 going to 3.3V through the resistor per the diagram I linked. It unfortunately did not change anything. I used a different 6N138 when I made my second MIDI board but they were both from the same manufacturer. I want to try Raspian, but it sounds like I will need to figure out all the steps from different sources. I have a Pi 4, and that post was 2017. Getting Munt to work with the GPIO MIDI IN is the challenge. If I can't figure it out, maybe you can tell me all the steps in a list of what to do from scratch. I can install Raspian from the imager tool and I am very familiar with Linux. |
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No problem, I'll do a quick write-up of how to test it in Raspbian shortly. I've noticed another mistake - in my breadboard diagram, the connections from the MIDI DIN plug are reversed, and it's because the tool I used to draw it (Fritzing) has an incorrect pin mapping for the DIN plug pins - the schematic is OK though. I doubt this will be affect you though, as you mentioned soldering and I guess you followed the schematic and not the breadboard. I'm still interested in seeing how you've built your interface! |
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Thank you very much. I would really appreciate the write-up for what all to do in Raspian (including setting up Munt and using it with the GPIO midi port). For the MIDI DIN, I went by the numbers on the schematic and the numbers embedded in the plastic on the MIDI connector. I have uploaded pictures, so maybe you can check if it is right. Here are the pictures: Those are from my first midi interface that I made before changing it to 5V and changing the diode. My second interface is soldered to the pins on the Pi Hat because I am trying to make it fit into a case and there is not enough room for the push-on connectors. They are basically the same though. Thanks again! |
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Hi Michael, Thanks for the pictures - it looks like a nice neat construction. I can't see anything obviously wrong but it's quite hard for me to tell with prototype board. Sorry for the wait on the Raspberry Pi OS setup steps, it took me quite a long time, but here's a new wiki page where I'm going to be putting troubleshooting info from now on: https://github.com/dwhinham/mt32-pi/wiki/Troubleshooting I can play your Pink Panther MIDI without any hanging notes on this setup with my breadboard GPIO interface and an Arananet Pi-MIDI hat. Let me know how you get on! |
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Thank you very much! Your instructions worked perfectly, but I had to restart mt32emu-qt after rebooting (this was obvious but thought I would mention it). The results are exactly the same with the same hanging notes. If I play the MIDI file directly in Munt, it sounds fine. So, I guess the next step is to order a new 6n138 chip or try an alternative chip like the H11L1. I may also try putting the 0.1 uF capacitor on the midi pin 2 to ground before I do anything else. Edit: I tried adding the capacitor and it did not help. Thank you so much for all of your efforts. https://www.reddit.com/r/AskElectronics/comments/ci4b8e/6n_137_vs_6n_138_vs_6n_139/ |
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No worries, I'm glad you were able to follow them! Unfortunately I don't know what else to suggest; my electronics knowledge only goes so far and I've just been using circuit designs that others have shared. But at least we know for certain that it's a hardware issue in your case. Hoping someone might chime in with a suggestion or feed back their own experiences, or maybe it's worth asking in that subreddit - I'd love to hear if you get any further! |
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Thanks! My parts should be here by Friday. I have two methods to try so
hopefully one or both will solve the problem. I will keep you posted.
…On Tue, Aug 25, 2020, 1:57 PM Dale Whinham ***@***.***> wrote:
No worries, I'm glad you were able to follow them!
Unfortunately I don't know what else to suggest; my electronics knowledge
only goes so far and I've just been using designs that others have shared.
But at least we know for certain that it's a hardware issue in your case.
Hoping someone might chime in with a suggestion or feed back their own
experiences, or maybe it's worth asking in that subreddit - I'd love to
hear if you get any further!
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I would strongly suggest using the H11L1 (e.g. the ON Semi H11L1M) over the 6N138. It has an open-collector schmitt trigger output, so still needs the pull-up resistor, but unlike the 6N138, the detector side is specified for a 3v to 15v supply voltage, so you can power it from the 3.3v supply without having to use a resistor divider to get the output to acceptable voltages. If you do change to the H11L1M, keep in mind that it's not pin compatible with the 6N138. Cost is a little higher, 91¢ for the On Semi H11L1M at Digi-Key at qty. 1 compared to 81¢ for the Lite-On 6N138 at Digi-Key, but negligible if you're only buying one. The -0.5v to 7v for the 6N138 quoted above is misleading. That's from the "absolute maximum" section of the data sheet, that lists the voltages that can be applied without damaging the chip, not the voltages it works at. A traditional 6N138 is specified to work with a 4.5v to 5.5v supply. Some chips may work from a 3.3v supply, but it's working outside its intended voltage range. |
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Thanks for this info and clarification on my misleading interpretation of the datasheet. I couldn't find any better information to help @thorr2 on my own - sometimes, the only way to get the right answer on the Internet is to say the wrong answer so that someone will come along and correct you. 😄 I guess 6N138s that work at 3.3v are just from blind luck. It'd be great to have a better example schematic up here based on the H11L1, so I'll order one too shortly and maybe we can improve the design. |
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@Braincell1973 I've just noticed your nice MIDI I/O board has an output DIN - this is very useful and should give you what @icb- described above. It would be very interesting if you were able to use the above build, put the "not working" USB MIDI interface into the Pi's input, and use a second interface on the Pi's output. Then you could use Munt on the PC to receive from the 2nd interface and compare the sound to what the Pi is outputting. If what's received from the Pi is good, then Hope this makes sense! |
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Just tried the new kernels, there are still hanging notes and similar behaviours with MI1 and MI2 intros. Still no messages on the OLED display of my PI-MIDI besides "Lucasfilms Games" and the instrument indicators. About logging the MIDI out, I'm afraid I would be useless with a soldering iron if I had one, but MiSTer solution is based on open source code running on Linux, so I wonder if it's possible to log the MIDI data at a software level (and if that would require involvement from the MiSTer dev) EDIT: One detail, not sure if it's of any help, when I disable "delaysysex" on MiSTer midilink.ini, things get much worse, even when using CM-32L ROMs, just saying because this is supposed to be needed only for Rev. 0 of the MT-32, which could not keep up with... the speed of the sysex messages? so my feeling is that if I could delay the sysex (whatever this means) even more, it would get fixed. Without delaysysex is like there is a random "ding" or a sustained "wowowow" every few seconds, with it I can definitely recognise the music, but there are issues on it. |
If you have a second Raspberry Pi, you can use the You can connect the TX pin of one Raspberry Pi to the RX pin of a second Raspberry Pi, or the output of the optoisolator circuit to the RX pin of two Raspberry Pis. You just have to make sure you're not creating ground loops, by using isolated power supplies or connecting both Raspberry Pis to the same power supply. |
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@dwhinham yea I can try anything but I only have the 1 midi cable....... . From my perspective, my setup had major latency issues going from a keyboard to serial midi and as soon as I went from the midisport 2x2 everything worked fine , so as far as I can reason the hardware and mt32pi is fine , the only difference was the drive to the opto and the change of rom....... I'm going to see if I have a 2nd cable in the loft and use the midi in out and thru on the midisport to see if it enables the 2 keyboards I tried to work......... |
Thanks, I've got most of this documented over on the troubleshooting page (thought not the @Braincell1973 Cool, thanks - any more test results will be very useful. Cheers both. |
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@dwhinham - I did hot plug HDMI before, so this time I did it correct ;) and got an output. Ok this might be something you always do, but we are not (or not all of us) - Turning on Pi power when music/midi/scummvm is playing. I have noticed that things sound very different in a good way, many more notes etc, if I power on when Monkey Island 1 is running and not before. I still get hanging notes, but the sound is very different. Picture on left is MT32-pi running before starting ScummVM. Picture on right is when I power on while music is playing Thanks |
Great 😃
That's because the synth won't have received any of the SysEx or program changes to set instrument parameters and assign instruments to parts, so you'll hear music, but all the instruments will be wrong. This setup data is often sent out just once at the start of the song. Your logs look fine, although you should set I'm guessing that when you switched-on while the music playing, an incomplete message got interpreted as an Active Sensing command, hence the "Active sense timeout". |
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As advised by @dwhinham I'll report in this thread. Also experiencing these weird "notes not playing" problems. Here's a more detailed info regarding the setup: Rpi 3b+ Tested with the following controllers: Kawai K1-II (ch 2) Sample rate and buffer size don't affect the problem. |
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I've just had an absolutely shocking idea while reading MIDI specs. How on earth have I never heard of this?! An account of similar experiences here: http://blog.cornbeast.com/2012/12/beware-of-midi-running-status/ If the firmware of some USB interfaces "optimise" outgoing packets by using the Running Status feature, it would explain everything. I will try to implement this as soon as possible. Please stand by. 🤞 🤞 🤞 |
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Testers with hanging notes: Please try this build: As usual, unzip the kernels and try as much gear as possible. Anxiously awaiting your test results! 🤞😄 |
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Applies virtual pat on back :) Rpi3 1.2GHz Over the next few days I will try again my AMIGA and see if the last note hangs when exiting the game, and even when AMIGA is powered on/off needing the RPi to be power cycled to stop. |
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Hopping on the party boat, can verify this works. Raspi3 1.2GHz + PI-MIDI board |
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I think we can call this resolved. What a ride! First of all, many thanks to all of you for your patience and for taking the time to test, report, and brainstorm ideas for the underlying cause. I sincerely apologise for being suspicious of hardware when such a critical MIDI feature was missing from the software. I was so convinced of it being hardware that I couldn't see the forest for the trees. 😞 I'm still quite shocked that I'd never heard of MIDI Running Status, and a lot of sample code out there seems to lack it. But it was right there all along in the specification. Still, it's good that popular hardware schematics have been scrutinised here, big thanks to @icb- especially for that. I will update the example schematic soon with the H11L1 alternative as it allows a simpler, safer design and avoids the possibility of underpowering the optoisolator. You've all been given credit in the release notes for v0.4.0, which is now available. I hope that's the end of this issue! 😄 @Higgy69 If you still get a final hanging note in your Amiga game, please feel free to open a new issue. I think it'll be a different problem (maybe we need to implement a reset command or something), but I have Amigas over here too for testing so we can talk about it and test. Thanks again all, and I hope you can now enjoy |
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Works like a charm :D Thank you soo much @dwhinham for this lovely piece of software 🥇 |
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Thanks for not giving up, it's hard is to troubleshoot an issue one cannot reproduce, MT32-PI is now running perfectly for me! |
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My pleasure! 😄 Thanks again for your patience. |
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I got back from my trip and just got a chance to try the new version. I
can confirm that it mostly fixed the problem. I don't have any further
time for testing right now, but Pink Panther sounded correct until the very
end. At the end, the last notes hung for longer than I was expecting,
especially the cymbal drum. There might be a problem at the end of the
song where it doesn't send the "all notes off" or something. I only tested
the one song and didn't try it in Munt on my PC because I don't have time.
Thanks a lot for all of your help!
…On Thu, Sep 3, 2020 at 1:57 AM Dale Whinham ***@***.***> wrote:
My pleasure! 😄 Thanks again for your patience.
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I tried one more song and it ended properly. I think everything is fine.
Thanks!!!
…On Thu, Sep 3, 2020 at 10:58 AM Michael Hart ***@***.***> wrote:
I got back from my trip and just got a chance to try the new version. I
can confirm that it mostly fixed the problem. I don't have any further
time for testing right now, but Pink Panther sounded correct until the very
end. At the end, the last notes hung for longer than I was expecting,
especially the cymbal drum. There might be a problem at the end of the
song where it doesn't send the "all notes off" or something. I only tested
the one song and didn't try it in Munt on my PC because I don't have time.
Thanks a lot for all of your help!
On Thu, Sep 3, 2020 at 1:57 AM Dale Whinham ***@***.***>
wrote:
> My pleasure! 😄 Thanks again for your patience.
>
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Tested on my 2 keyboards and things much improved.... Yamaha pss680 works perfectly No change from scumm on pc , works very well. But , As I have never owned a mt32 I cant verify this next thing , on the pc, whilst scumm seems to work properly, playing regular midi files to the mt32pi results in musical oddities , rather like its missing a track, if that makes any sense. I can compare the output to the mt32 and Windows wave table and its like there's details missing ?? I read somewhere that the mt32 has a reserved track 0/1 ????? Anyway , thank you for this fantastic device |
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Braincell1973,
I haven't been following your messages, so I can't comment on the MK449 as
I am not sure how you are using it. Regarding the last couple of
statements about playing regular MIDI files, this is normal behavior
because you are trying to play General Midi files with the MT-32, and the
MT-32 is not General MIDI compliant. Search for Roland MT-32 MIDI files
(that have not been converted to General MIDI) and they should play
correctly. The Pink Panther MIDI file that I linked to at the beginning of
this issue is a Roland MT-32 file.
Try these: http://ftp.monash.edu.au/pub/midi.songs/MT-32/
Hope this helps.
…On Thu, Sep 3, 2020 at 1:16 PM Braincell1973 ***@***.***> wrote:
Tested on my 2 keyboards and things much improved....
Yamaha pss680 works perfectly
Mk449 works mostly but cuts some notes short...... ( unsure if its
keyboard ??? )
No change from scumm on pc , works very well.
But , As I have never owned a mt32 I cant verify this next thing , on the
pc, whilst scumm seems to work properly, playing regular midi files to the
mt32pi results in musical oddities , rather like its missing a track, if
that makes any sense.
I can compare the output to the mt32 and Windows wave table and its like
there's details missing ?? I read somewhere that the mt32 has a reserved
track 0/1 ?????
Anyway , thank you for this fantastic device
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@thorr2 The Pink Panther MIDI has a cymbal and an open hi-hat at the end. Here are the final bars:
The open hi-hat sound on the MT-32 goes on for quite some time, almost 5 seconds! The cymbal has a pretty slow decay too. It sounds identical to me on both desktop Munt and I did some testing (both Munt and Sounds good - can you check the behaviour of the Mk449 on desktop Munt when you get a chance? You can get the latest Windows version here. Playing regular General MIDI files will rarely sound correct on an MT-32 (or an emulation of one) - the MT-32 pre-dates the General MIDI standard, so most of the instrument mappings will be wrong, and as you've noticed, channel 1 is reserved. It's possible to get somewhat close though. On a real MT-32, holding some buttons down on startup will change the default channels from 2-9 and 10 to 1-8 and 10 (10 is always for drums). Additionally, Roland published some .MID files full of SysEx that try to remap the MT-32 instruments to resemble General MIDI. It's nowhere near perfect, but it's fun to try. If you grab the But this isn't really the intended purpose of the MT-32 - you want to find some songs composed for the MT-32 such as the ones @thorr2 has suggested. 😃 |
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@dwhinham Just wanted to let you know that after these latest updates, mt32-pi is working perfectly also with the pc-midi card (http://pcmidi.eu/). There were all sorts of strange hiccups which are completely gone with 0.5.0. Nice work! |
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That's what I like to hear - excellent! 🎉 Thanks for the feedback 😃 |
Hello, I just installed this for the first time and made my own MIDI adapter for the GPIO pins using your schematic. I hooked up an OLED display and it works properly. Munt is missing some note-off's and it is consistent (always happens in the same places in the same songs). I am using Monkey Island 2 for example on my MiSTer and the music always has hanging notes in the same places that should not be there. The display shows these notes hanging. I have tried different chunk sizes (32 and 2048) and set my frequency to 32000 and the scaler to none. Nothing so far seems to help. Any ideas what could be causing this? I have also played Doom on my MiSTer with my Roland SC-55 mk2 and it works fine with no hanging notes, so that is not the cause. I also tried playing to the mt32-pi from my PC and it also has hanging notes. Thanks for your help.
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