charles wrote:probally will need some enhancing ,
because even with a midiex and me using only two ports , my midi latency was greatily increased.....unstable timing and program becomes non responsive..
I have a rs232 midi port expander however have not tried it yet ,,
I do believe this should solve the latency issue as its not all coming out of the same port
hasbab wrote:I've heard that C-Lab even warned against using Export (RS232 midi port expansion) for high bandwith applications, such as mod wheel changes, it was only really recommended for note on and note off messages.
It's pretty difficult to find anyone who has performed this upgrade recently, or to find any info on performing it without programming a GAL chip
RSVE - the hardware to speed up the MODEM1 serial port of Atari ST, STE, MegaST, MegaSTE and TT to 38400 and 57600 (and with good luck 115200) bps while still keeping the old data rates. Hint: RSFI is much better.
Download RSVE_GE.LZH (25 KByte)
Foxie wrote:For MIDI output it's interesting. I'm designing a MIDI interface device which connects to the modem port and gives you four outputs. You should be able to get nearly full bandwidth on all four ports at once. The downside? There's no drivers for Cubase or anything else yet! There's a thread about that problem here: viewtopic.php?f=111&t=32977
Simply cranking up the serial port rate is no good by itself. You need special hardware like a specially designed MIDI interface device attached to the modem port to make use of it. Export simply won't work with these higher baud rates.
The reason Export performs so badly is because it's a bit of a fudge. It sets the modem port to 31.25k baud (same as MIDI), and squirts MIDI data out. Export then relays this to one - and only one - of the MIDI ports, unchanged. Export has literally no intelligence at all, it's £0.50 worth of parts. It's more like a simple cable than a MIDI interface. That's fine for driving a single port - it will give you full bandwidth just like the built-in Atari MIDI ports. Contrary to popular belief, it doesn't matter which single port you use either. But if you drive all three ports at once, Notator or Cubase will switch between them rapidly. It sends one MIDI event at a time to each port. Transmission on port 1 has to complete before it can start on port 2. It's completely unable to transmit events simultaneously out of all three ports - it has to time-share. That means your bandwidth is cut into a third! It's no better than using a MIDI thru chain.
hasbab wrote:Hi everyone,
[…] It also mentions that higher modem speeds are impossible without an accelerator.
I have two questions if anyone is able to help:
2) Will a serial port enhancement to add additional midi channels to the ST require hardware acceleration in order to perform without excessive latency?
charles wrote:midi is meant to be its own speed , isn't it technically set to 31 kps for a reason?
Fujiyama wrote:Does this mean that if you do succeed with the Cubase drivers there still won't be any hope for improvement for Notator users using that 4-port MIDI interface of yours?
Fujiyama wrote:So improving the serial port with an RSVE or similar won't make any difference and is a waste except if a modem is to be attached to that serial port as well? This is probably one of those situations when "if it sounds too good to be true it usually is".
Fujiyama wrote:These add-on boxes cost quite a bit back in the day and I would never have imagined it working that badly.
Fujiyama wrote:So it all boils down putting it to use in a smart manner: resisting to use all 3 ports and instead just settle on one additional OUT from that expansion box.
charles wrote:I think its the cpu speed you need to improve .
midi side of things is ok .
so double clock the cpu and viola ! ???
charles wrote:that's a huge task you've set aside for yourself , hope all goes well
charles wrote:and if you have time im interested in learning about a vertical blank timer to use in my sequencer/playback routine
u breifily hit on in one of your previous posts
Miguel wrote:The other thing I built was an adapter to separate the Atari's MIDI out and MIDI Thru, the advantage of which is not monitoring your playing using the soft MIDI Thru which adds about 2ms of latency over using the hardware MIDI Thru.
Miguel wrote:The main advantage of the Atari is actually it's input latency because that's something which can't be compensated for by time stamping protocols such as LTB which sends MIDI data ahead of time from the sequencer tracks of Cubase to the more modern discontinued MIDEX interfaces.
Miguel wrote:Yes Foxie I actually measured the 2ms latency between the Atari's MIDI Thru port and the Atari's MIDI Out port (using soft MIDI Thru) by hooking up two identical Akai S2000 samplers to each port on the Atari and each audio output to a DAW for comparison.
Miguel wrote:USB is not very good at all for MIDI input however like I said it is possible to get really good timing by using a MIDI time stamping to send pre-recorded MIDI data ahead of time for release by dedicated hardware, that's how Cubase's LTB works with the MIDEX8 interface,
Would a Steinberg Midex+ interface do the right job?
As it happens, I do have a lot of data on that.
There's the schematic diagrams, GAL files and data for the modification. (Originally the Midex has PAL's)
And there's a document for a Falcon mod. (That I've not tried yet)
Also, I have test programs.
For one, it's possible to (re)make the midi-ports and SMTP-bit. (Skip the Dongle ports)
If this helps, let me know and I'll send the stuff. (PM-me-too )
All data files are too big for upload to this forum.
guus.assmann wrote:Hello Foxie,
The full schematics in a four sheet PDF, sometimes a bit hard to read, but ok.
And the Jedec files for the main GAL, as well as the data to create this GAL. (20V8)
And the Jedec file for the SMTP-Gal, a 16V6
So in my opinion, enough to recreate a Midex+ expander.
Just let me know an E-Mail address and I can send the stuff, so you can see for yourself.
edingacic wrote:Wow, nice Foxie. I have TT030 with Midex+ and Sound Pool Mo4 if you want I can do some tests for you as far as timing you are talking about but you need to give me some direction and tools how to do that.
edingacic wrote:After reading everything that you have mentioned in your responses what I think you should look at is the Friendchip MM1 MIDI interface.
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