MiST and MIDI questions

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Re: MiST and MIDI questions

Postby MasterOfGizmo » Fri Sep 26, 2014 5:40 am

As I said: I don't know if my solution actually works. But I am optimistic. If you still measure this now 0.001% error I can try to improve it even further.
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Re: MiST and MIDI questions

Postby MasterOfGizmo » Fri Sep 26, 2014 11:00 am

So is the timing better now?
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Re: MiST and MIDI questions

Postby novoline » Fri Sep 26, 2014 4:09 pm

Ok, I'm back from my gruelling tests. :contract: Good news first: Its real damn close! Totally usable, particularly with my 1040STe when the MiST is set to STe.

I learned some interesting things tonight, not just about MiST but about my two main Ataris as well (a Mega1 and a 1040STe with 4MBram)

My longest, and first test, was 47 minutes, Mega1 vs MiST in STe mode (which I have set as my default)
92bpm, 8th notes.

After 47 minutes the MiST was slower by 0.0377 seconds. While taking data points down I started to notice a fluctuation, and I figured out that the Mega1 (and later saw the same in the STe) will jitter around a consistent speed, usually a stutter (i.e. triggering a sound late) by as much as 0.0085 and an average of 0.0070 seconds ( those numbers based on just the analysis of the 47 minutes with 99 data points :| ) But then it jumps back on the next tiggered note to the normal time it should.

After writing down all the data points, which meant having the MiST idle there for around an hour (so it was on for a total of circa 2 hours at this point still in the program), I wanted to do a second trial. To my surprise the MiST was WAY off in comparison to how it was even with the last core, it would get behind by a full 1/8th note in less than two minutes. Remember the last core, it would do this in 20!
I restarted the MiST with the front switch and was still doing it. I restarted again with the back power switch and saw that the syncing was back to what it was previously.
Then I decided to compare my real machines: the Mega1 and STe. I discovered that the Mega1 is eeevverrr so slightly faster. So then I did a test using the STe and the MiST, and they were really close. Closer than the Mega1. I didn't take exact notes as I would have been there all night, but after 10 minutes i saw NO significant lag, and with jittering in the STe's notes.
This made me think of testing out the different chipsets in the MiST, maybe the MiST Mega STe will be closer to the Mega1, right?
Nope! Not quite as bad as the on-for-2-hours MiST STe (which I didnt have time to try and recreate to see if it was reproduce able ) but for all three other chipsets (ST, MegaSTe, STeroids) the timing was off. A full 1/8th note off in ~3 minutes. It was so off that I didnt bother taking notes on them but later when I take a look i can tell you which ones were going faster or slower; right now i don't remember. I think the ST and MegaSTe were running slower and the Steroids faster but I'm not quite sure of this right now. (Thank goodness my MiST was booting the STe -- or I would have been giving you crazy numbers! )

Then I rebooted back into MiST STe, ran my 1040STe against it two more times with clean boot in between to confirm they were running together. They were. It's a winner (as long as you use STe!) :cheers:


One very interesting aspect of the real Ataris is this stuttering. I'm quite sure its why I love using them so much, it gives a little life to the music that isn't recreatable with, well, anything, not even the MiST! This is probably a ridiculous question, but is that sort of precision/imprecision dynamic possible on an FPGA? Probably not i know, definitely not suggesting you try, just curious :mrgreen:

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Re: MiST and MIDI questions

Postby novoline » Sat Sep 27, 2014 2:13 am

bumping because i edited the last post..

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Re: MiST and MIDI questions

Postby novoline » Mon Oct 20, 2014 9:35 am

Hey There All.
So I'm back from an international trip wherein I performed 7 concerts with two MiSTs instead of two Atari STs. What a great space and weight saving time I had! I was able to get two cheapie LCDs with full RGB adjustments for 10 bucks each, brought down the green and blue so I had an eye-pleasing red monochrome. I also picked up an asernal of thrift store usb keyboards and mice, at a dollar each I was able to get some backups.
Overall I'm really thankful to have these boxes, and I turned a lot of people onto them as well. I've got a couple of things I want to point out though,

I've made a crucial observation about the timing behaviour on the trip. I didn't have a real ST for timing reference but this deals with the two MiSTs on their own:
I found out the hard way that the timing will sometimes be off on the MiSTs. One will be running slower (or faster depending on your optimism) by a big factor, after only 10 seconds its really perceivable, unplayable as a duo. Rectifying the sync problem was a matter of resetting over and over, starting up the program on both MiSTs each time and playing them and listen, then try again. From my experience so far, it seems I've got a circa 2 in 5 chance of getting them to run together at the same speed. Front reset button vs. rear power switch reboot doesn't seem to change the odds.


The second observation is that after doing the 100ohm modification on r1 and r3, the MIDI output is powerful enough to run a Midi Solutions Quadra Thru (which is what I tested with after I finished the mod), but not powerful enough to run a Midi Solutions Midi Merger, which is unfortunately what I need the midi power for (to merge the two Atari midi signals.) I didnt expect the two boxes to have different power requirements.
I overcame the limitation somewhat by doing some rerouting in my signal path, and at home I also have a Phil Rees merger that is wall-powered that I can use next time if this can't be overcome, but the ability to use a MIDI powered merger would be optimal as it takes up less space and is one less thing I need to plug in.
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Re: MiST and MIDI questions

Postby MasterOfGizmo » Mon Oct 20, 2014 8:05 pm

I was actually a little afraid of that. Your explanation of the different modes (st, ste, steroids) showing different speeds didn't make much sense to me. I was expecting something like this 2 out 5 behavior you now describe instead.

What I don't fully understand: Do you have to switch off and on again to trigger a change in speed? Or is it sufficient to reload the core using the reset button right beside the sd card slot?

The board uses a so called pll to derive the various system clocks from the 27mhz oscillator on board. I wonder if it's the pll or the oscillator that shows this behavior. If reloading the core without power cycling has an effect then i'd assume it's the pll as that's part of the core while the oscillator will just keep running unless you power cycle.

This all is some special component provided by the FPGA itself. I might ask the vendor if there's something that could affect it in the way you describe.

Another question: Is the magnitude of error constant? Is it wrong in the same way whenever it's wrong?

And finally: Is there a video of such a concert? I'd like to see that.
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Re: MiST and MIDI questions

Postby MasterOfGizmo » Mon Oct 20, 2014 8:18 pm

Ah, rereading your last post I understand that power cycling as well as reloading the core affects this. My guess now is it's the pll. Now I have to find out if there's something I can adjust.
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Re: MiST and MIDI questions

Postby MasterOfGizmo » Mon Oct 20, 2014 8:27 pm

Two more remarks: It's possible to build cores that generate black 'n red video without further need to modify any hardware.

And second: You are using quite big computer keyboards. Do you need them while performing? If not then some tiny wireless media center keyboards may be nice. I personally like the rapoo e2700.
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Re: MiST and MIDI questions

Postby foft » Tue Oct 21, 2014 6:32 am

Be interesting if the pll has multiple stable states.

I guess you could run a counter off pll and the crystal to check this.

If seen there is the question of what to do. Perhaps the core could monitor both. The pll allows reconfiguration without restarting the core. Not sure how much this repeateded check/reconfig would add to boot times! Or perhaps an st speed crystal could be put on the board. Hopefully there is just a magic setting on altpll!

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Re: MiST and MIDI questions

Postby novoline » Tue Oct 21, 2014 11:52 am

MasterOfGizmo wrote:Another question: Is the magnitude of error constant? Is it wrong in the same way whenever it's wrong?



More testing would need to be done.* Not sure. By what I heard, I would say there's more than one different speed. As I said before I didnt have a real ST there to reference, so probably sometimes when they booted up in sync, they were in sync on a slower speed than real ST.
*I probably won't have time to do further testing until November

MasterOfGizmo wrote:And finally: Is there a video of such a concert? I'd like to see that.


If you mean video of a concert when it was not synced, i didn't seek it out, because it was an awful set! I don't think anyone bothered that night. At that point I didnt understand what the problem was. I only did one concert unsynced before realising I could fix it by the multiple resets.
I know theres video and audio of some concerts from the trip wherein I stayed in sync, I'm still waiting on files to be sent to me.

MasterOfGizmo wrote:Two more remarks: It's possible to build cores that generate black 'n red video without further need to modify any hardware.

I haven't built any cores but I'd love to learn how so i could have multiple monochrome colours to choose from. (and a nice green for the appleII+)

MasterOfGizmo wrote:And second: You are using quite big computer keyboards. Do you need them while performing? If not then some tiny wireless media center keyboards may be nice. I personally like the rapoo e2700.


Unfortunately yes I need the whole keyboard. For sure the numeric keypad, spacebar, esc and backspace. Function keys and arrow keys 2nd most important after that group, then the rest of the keyboard for smaller changes. If i want to be really streamlined I could get away with something like the Cherry G84-4700, but I haven't been able to find out for sure if one of the programmable keys on top can be programmed to spacebar, which is the most important; "Start."

*edit*
here's the one video i know of via instagram, post-syncgate, pre-redmonitor. http://instagram.com/p/uHTthcn2dV/

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Re: MiST and MIDI questions

Postby MasterOfGizmo » Thu Oct 30, 2014 3:25 pm

I may have found something regarding the clock settings. I've sent you a PM.
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Re: MiST and MIDI questions

Postby knabo » Tue Nov 11, 2014 4:20 pm

MasterOfGizmo wrote:This limits the current to 5V/3*220ohms = 7.5mA in short circuit or 5mA if the opto couplers LED on the receiver side drops 1.7V as (5V-1.7V)/3*220ohms = 5mA. This is what the MIDI standard assumes.


I want to mention that I just tried an M-Audio Midiman Thru 1x4, parasitically powered by my unmodified MiST, and it works just fine.

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Re: MiST and MIDI questions

Postby ryan » Mon Nov 17, 2014 2:54 am

I haven't played with my MiST much yet, keep meaning to. But I'm curious if the firmware could be modified to host class compliant MIDI devices and then just front them to the core as the ACIA, much the same way the SD card fronts a fake floppy. Then no need to ship MIDI hardware on the device itself.

That and getting a verilog emulation of the Notator dongle going. I started to hook my Salae Logic 16 up to the cartridge port of my 1040 running Notator, but it's awkward -- a) not enough pins on the logic probe b) can't reach half the pins. Might be easier if I cracked open the dongle, as I have two of them, but that makes me nervous, especially given what I see second hand Notator going for on ebay, etc.

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Re: MiST and MIDI questions

Postby knabo » Tue Nov 18, 2014 1:47 am

ryan wrote:I started to hook my Salae Logic 16 up to the cartridge port of my 1040 running Notator, but it's awkward -- a) not enough pins on the logic probe b) can't reach half the pins. Might be easier if I cracked open the dongle, as I have two of them, but that makes me nervous, especially given what I see second hand Notator going for on ebay, etc.


You could also get yourself an edge connector, wire it into a breadboard, then wire it out to a card connector harvested from a cheap/broken cart to make things easier. Till was analyzing Cubase dongles before so he may already have a more clever solution.

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Re: MiST and MIDI questions

Postby ryan » Tue Nov 18, 2014 3:27 am

So I was thinking of taking that approach, but wasn't sure I'd find a card edge connector of the right pitch. I had read a posting somewhere indicating it was hard to get the connectors to work with the ST's cartridge port anymore. But yeah, if I can do it, not a bad idea.

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Re: MiST and MIDI questions

Postby MasterOfGizmo » Fri Nov 21, 2014 7:30 pm

MasterOfGizmo wrote:I may have found something regarding the clock settings. I've sent you a PM.


I just got a PM from novoline indicating that this latest fix actually solved the problem. He's consistently getting a replay rate within acceptable limits over a long period of time.

Seems the MiST is pretty close to being a perfect ST replica when comes to MIDI at least. :D
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Re: MiST and MIDI questions

Postby MasterOfGizmo » Fri Nov 21, 2014 7:33 pm

foft wrote:Be interesting if the pll has multiple stable states.


The problem is with cascading PLLs. They jitter a little while they try to generate the required target frequency. At the same time they need to deal with jitter on the incoming signal. Now the second PLL needs to deal with the jittery output of the first one and that seems to lead to trouble.

Fortunately there are filters in the PLLs which can be used to make sure the first PLL doesn't generate much jitter and the second one to not be too sensitive to input jitter. It seems this solves the problem.
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Re: MiST and MIDI questions

Postby prprp » Wed Nov 26, 2014 1:44 pm

Hi,

Has anyone carried a MIDI litmus test (as defined here: http://www.innerclocksystems.com/new%20ics%20litmus.html) of an MiST running Cubase (or other similar software) as a slave to MIDI clock ?

I believe the MiST could be a big hit amongst musician working with external hardware if the results are good, as nothing keyboard/mouse based and available today is quite as musically "tight" as an Atari - only they have become much too slow to work with compared to PCs...

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Re: MiST and MIDI questions

Postby knabo » Thu Nov 27, 2014 10:09 pm

Just saw this in my YouTube feed: https://www.youtube.com/watch?v=K-DmpZPaB2g

Very exciting! Does this mean I'll get to finally try Bars n Pipes?

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Re: MiST and MIDI questions

Postby k2500x » Tue Jan 06, 2015 12:14 am

I'll be keeping a close eye on this thread.
If MiST really does work 100 percent like a real Atari Ste with perfect timing and enhanced resolution I'll be picking one up.
To think of all the money and time I've spent trying to get the real hardware functioning in a usable state in 2015.

If this had access to my MIDEX+ (or a way to get multiple MIDI IN/OUT) it could be the ultimate MIDI sequencer of all time!

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Re: MiST and MIDI questions

Postby teevee » Sat Mar 21, 2015 1:33 pm

Very interesting, any news? :)

Have you guys tested it with other midi programs, than Cubase? :)

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Re: MiST and MIDI questions

Postby knabo » Sat Mar 21, 2015 9:12 pm

I started a spreadsheet a while back for keeping track of compatibility for midi applications just for myself, might be useful for others: https://docs.google.com/spreadsheets/d/ ... sp=sharing

Haven't updated it in months though, so might need to try some things out with the newer cores/firmwares and update.

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Re: MiST and MIDI questions

Postby teevee » Sat Mar 21, 2015 10:12 pm

knabo wrote:I started a spreadsheet a while back for keeping track of compatibility for midi applications just for myself, might be useful for others: https://docs.google.com/spreadsheets/d/ ... sp=sharing

Haven't updated it in months though, so might need to try some things out with the newer cores/firmwares and update.


Thanks for that, I look forward to hear/see your update on Steinberg Cubase and Notator SL :)

Other things I think could be interesting to see is Mist’s compatibility in case of:
• MIDI sample dump (example Steinberg Avalon 2)
• Sysex (with editor for synthesizer)

Would be cool if someone could break those dongle things :)

I wonder if we soon can try Midi on the other emulations too? :shrug: (Example Amiga)

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Re: MiST and MIDI questions

Postby eeun » Sat Apr 25, 2015 4:55 pm

I was looking at the midi interface schematics and I'd like to take a crack at etching a board.
Is is possible to get access to the Eagle file (assuming it was done in Eagle) for personal use?

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Re: MiST and MIDI questions

Postby eeun » Sat Apr 25, 2015 4:56 pm

Duplicate post :(
Last edited by eeun on Sun Apr 26, 2015 5:31 pm, edited 1 time in total.


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