C-Lab Export: unidentified IC

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C-Lab Export: unidentified IC

Postby Fujiyama » Thu Jan 18, 2018 7:43 pm

I've opened up my C-Lab "Export" (adds 3 MIDI OUT ports through the modem port with Notator/Creator SL) and found a single unidentified IC marked "EP210".

At Vezz' hardware site I found a project named "MIDI48" which is a similar MIDI expansion box, or perhaps it's more or less a copy of the Export. Anyway it uses a 74HC138. Could this be the same IC as the "EP210"?
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Re: C-Lab Export: unidentified IC

Postby czietz » Fri Jan 19, 2018 7:11 am

The fact that the IC looks like the part number etc. were stamped onto it with white ink makes it indeed more likely that this is a relabeled part. You could draw the schematic from the photo -- easy, as it's just a single sided board -- and see for yourself if a 74138 would fit.

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Re: C-Lab Export: unidentified IC

Postby Foxie » Sat Jan 20, 2018 7:49 pm

*facepaws at the painted numbers*

I had no idea they went to that "effort" to hide their "valuable" intellectual property!

Yep, this is just a 138. I checked the pinouts. Not sure if it's an LS138 or HC138, but probably the latter due to power consumption.

I'll have a go at tracing the schematic. It looks very similar to "midi48," but midi48 does have a couple of flaws - I'm wondering if the Export also has them.

I wonder where they got those slim DIN connectors from? AFAIR, "midi48" uses chassis-mount DIN connectors because ordinary PCB mount connectors wouldn't fit.

It's funny that they painted it over. I suppose they needed to hide the fact that the only chip is literally a £0.05 part. Even the plastic box is more expensive than the main chip!

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Re: C-Lab Export: unidentified IC

Postby Foxie » Sat Jan 20, 2018 8:44 pm

Fujiyama wrote:I've opened up my C-Lab "Export" (adds 3 MIDI OUT ports through the modem port with Notator/Creator SL) and found a single unidentified IC marked "EP210".


Would it be possible to read the two capacitor values in uF? I can't see them in the top-view, and it would be nice to have a complete schematic with correct component values.

Also, I don't suppose it's possible to tell from inspection which of the diodes are zener diodes? They might be marked with a value like 5.1.

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Re: C-Lab Export: unidentified IC

Postby Foxie » Sat Jan 20, 2018 10:32 pm

I finished tracing the Export schematic. Here it is:

C-lab export schematic.png


It's not a very good design. But guess what? It has the same mistake as the "midi48" unit!

Pin 6 is wired, but pin 6 isn't connected on an Atari ST. It's completely useless! Perhaps they meant to connect pin 5 instead, which is CTS. That would be genuinely useful, because you could then poll the CD/CTS inputs to determine whether the handshake outputs have finished transitioning before you begin transmission. But since the Export isn't wired correctly (and nor is "midi48") you have to put a delay loop in the software instead. Or maybe the hardware designers had literally no clue about the Atari ST, and just assumed pin 6 (DSR) was wired like it is on the IBM. Very, VERY sloppy. I'm not pleased.

I'm also mystified by R7 - a 47K resistor from output Y7 to Vcc. Y7 is already at logic high, and it isn't used by anything. It appears to be a complete waste of a resistor!

I'm also not convinced that C3, R2, R4, and R6 are really necessary either.

Overall the design is very similar to "mdi48" but not identical. Midi48 has some unnecessary extra diodes. Neither "midi48" nor Export provide proper ESD protection. So be careful not to zap the MIDI ports or Modem port! This could have been easily added by replacing two of the diodes with zeners and adding four additional zeners. But alas, that would have cost them about £0.10.


Principle of circuit operation:

The 74HC138 directs the MIDI signal from the modem port TX line to one of the three MIDI outputs. The output is selected by pins 1 and 2 on the chip, which are wired to the two handshaking outputs on the modem port. The Atari first selects which port it wants to address by setting the handshake lines to 01 10 or 11, and then begins transmission after a short (couple of microseconds) delay to allow the handshaking lines to transition. The Atari needs to wait for a byte to fully finish transmitting before it attempts to select the next port. It's not enough to wait for the buffer to be empty - the shift register itself needs to be empty. I'm rather surprised they didn't connect TX to RX to generate an interrupt for this purpose.

Power for the circuit is derived from the two handshaking lines, through D1 and D2. Thus, at least one of the handshaking lines has to be positive at all times. This is why you can't select a fourth port with 00. I'm surprised they didn't use a third diode to suck power from the TX line too. This would allow driving phantom powered MIDI devices like merge boxes more easily.

Since the RS-232 levels are +/- 12 volts and the chip runs on 5 volts, a zener diode (D3) is used to limit the supply, through R14. C2 provides a store of energy at 12 volts (actually a bit lower in practice) to allow for brief power outages when the handshake lines transition (in case they go to 00 briefly when moving from 01 to 10). To be honest, using such a large capacitor is probably overkill for that.

R1, R3 and R5 limit the current into the chip. This is necessary because the RS-232 levels are +/- 12V, and you're not supposed to exceed the power supply voltage for a CMOS chip. A 22K resistor limits the current to a safe level, and the ESD protection diodes in the chip take care of clamping it to 0-5V. Note that the ESD protection diodes aren't big enough to protect against a really big static shock - you need external diodes for that. Sadly, they didn't bother to include any.

Not really sure about R2, R4 and R6. They don't appreciably affect the voltage on those lines being such a high value. My only guess is that they wanted the inputs to remain at defined logic levels when you unplug the Export, if the capacitor still happens to be charged. But honestly, I don't think it's necessary - even if the inputs do go into the linear region when you unplug it, it will quickly drain the capacitor before any real damage can be caused. Or they could have added a single bleeder resistor to ensure the capacitor discharges fully.

The 220 ohm output resistors are required by the MIDI spec. Though technically it violates the MIDI spec slightly because you're not supposed to drive a MIDI output's sink line high. But in practice, many devices do - including Emagic's rackmount Mac interfaces (which also have no ESD protection). It won't cause any harm to the receiving device, but it might stress both Export and the other device if you accidentally plug an output into another output.

C1 is just a decoupling cap, but C3 seems a bit unnecessary. I doubt the device can draw enough current for long enough to need that.

Export also violates the MIDI spec a little by its baud rate. The ST's serial port can be set to 30,720 baud, but not 31,250. That's a 2% baud error, twice the MIDI's spec of 1%. But in practice, it's probably fine with all devices.
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Re: C-Lab Export: unidentified IC

Postby czietz » Sat Jan 20, 2018 10:38 pm

Foxie wrote:I'm also mystified by R7 - a 47K resistor from output Y7 to Vcc. Y7 is already at logic high, and it isn't used by anything. It appears to be a complete waste of a resistor!


Notice that Fujiyama's photos show that the PCB would also accept a PDIP-20 package; thus a different IC. Maybe the resistor was needed for that one?

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Re: C-Lab Export: unidentified IC

Postby crashman » Sat Jan 20, 2018 10:46 pm

The capacitors are 220uF 16V.
The two middle diodes are marked 48F.
The one in the side... I can read 5V6, PH and BZX
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Re: C-Lab Export: unidentified IC

Postby Foxie » Sat Jan 20, 2018 11:00 pm

czietz wrote:Notice that Fujiyama's photos show that the PCB would also accept a PDIP-20 package; thus a different IC. Maybe the resistor was needed for that one?


It could be, but I have really no idea what chip that is. It would need to differ in only one pin.


crashman wrote:The capacitors are 220uF 16V.
The two middle diodes are marked 48F.
The one in the side... I can read 5V6, PH and BZX


Thanks! I've updated the schematic to reflect this. Also added some more information on the workings of the circuit.

Crikey, 5.6 volts? That violates the MIDI spec too! In fact it kind of violates the 74HC138's specs also. A 5.1V zener would have been a better choice. Maybe they were a little more expensive.

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Sat Jan 20, 2018 11:51 pm

Wow! Thanks for all the efforts you Foxie, and also the others who have responded here. I'm surprised to hear about all those mistakes. Could some of those hardware faults be rectified and thereby improve its performance, if only a little? Or does the software side of it (Notator/Creator) prevent any of those fixes to be recognized and taken advantage of?

Crashman is absolutely correct about the electrolytic capacitors: they're both 220uF/16V.
The diodes were a little harder to make out, but I'm pretty sure I read "48F" and "5V6" as crashman pointed out, but the third one looks like "41" here. See the attached photo.
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Re: C-Lab Export: unidentified IC

Postby Foxie » Sun Jan 21, 2018 12:29 am

Fujiyama wrote:Could some of those hardware faults be rectified and thereby improve its performance, if only a little? Or does the software side of it (Notator/Creator) prevent any of those fixes to be recognized and taken advantage of?


You probably won't get any improvement in MIDI performance, but you could make it more reliable / less likely to die from ESD. I propose the following mods, but they're completely untested - use at your own risk!

C-lab export modified for ESD.png


Note the green diodes need to be schottky.

It's remotely possible that Notator polls the CTS line, if the programmers were working on a different spec to the hardware designers. There must be some explanation for that screw-up after all! If this happens, Notator might time out polling causing a severe impact in MIDI performance. You can test that by glooping a solder blob between pin 5 and 6 on the modem connector. It's remotely possible that it might cause the software to malfunction, so be prepared to remove it again. What's weird is that they didn't do this modification in the production units.

The pins are here:

C-lab export bottom modified.jpg
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Re: C-Lab Export: unidentified IC

Postby Cyprian » Sun Jan 21, 2018 1:29 am

As far as I remember MIDI OUT needs exactly 31250 bps, and ST RS port has max 19200 bps. Therefore how does it work?
In additional, I see there three MIDI OUTs, 3 x 31250 = 93750 bps. Is it possible to reach 93750 through 19200 bps pipe?
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Re: C-Lab Export: unidentified IC

Postby Foxie » Sun Jan 21, 2018 1:55 am

Cyprian wrote:As far as I remember MIDI OUT needs exactly 31250 bps, and ST RS port has max 19200 bps. Therefore how does it work?


Maximum serial port rate for the ST is actually 307200 bps! However, if you want to use the input, that drops to 19200 bps. That's why modem users often needed to mod their serial ports to use faster modems. But if all you need is output only, you can go much, much faster.

To enable faster baud rates, you write to the USART control register (UCR). When bit 7 is set, the baud rate is 1/16th the timer D clock output. When it's clear, it's 1/1th the timer D clock output - 16 times faster. This is how you get 307200, and close to 31250. But when you enable this mode, the input needs to be synchronised with the timer D clock. That's extremely difficult or even impossible to do for an external device. So for most purposes, you can't use the input at higher baud rates. Hence, it's useless for modems - but ideal for MIDI.


Cyprian wrote:In additional, I see there three MIDI OUTs, 3 x 31250 = 93750 bps. Is it possible to reach 93750 through 19200 bps pipe?


Unfortunately, Export doesn't do what you'd hope it does. It simply multiplexes a single 31250 bps output between three ports. Only one port at a time can be driven. So, the total bandwidth is only 31250.

This is what I'm remedying with my MIDI interface device - it will run at 307200 bps, allowing you to completely saturate all four ports with data. But of course, no input is possible on a standard ST. (but you could do it on the MegaSTE/TT/Falcon, if I had one to develop software for)

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Re: C-Lab Export: unidentified IC

Postby Cyprian » Sun Jan 21, 2018 2:12 am

good to know,
maybe would be possible to connect two STs with 307200 bps
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Re: C-Lab Export: unidentified IC

Postby Foxie » Sun Jan 21, 2018 3:21 am

Cyprian wrote:good to know,
maybe would be possible to connect two STs with 307200 bps


I'm not totally sure how the well-known high speed modem port modifications work, but you could definitely make a modification that supports bidirectional comms at 307200 bps. You'd need a microcontroller that listens to the serial input and extracts the clock, feeding it to the UART receive clock input. While using a microcontroller, it may as well also generate its own clock instead of using timer D - allowing the use of more standard rates like 115200, 230400, all the way up to 921600 (about the fastest the ST's serial port can go with an external clock).

Of course TOS will be a problem, due to lack of buffering in the MFP. You'd probably want to turn interrupts off and poll the MFP to receive data. Or at least use byte-by-byte handshaking.

You could also use the printer port to connect two STs, since the ST has always had a fantastic bidirectional printer port. You could also connect an Amiga and ST that way. Connecting to an IBM printer port is a bit more difficult since the bidirectional support on IBMs stinks badly. And of course the Mac never had a printer port - a disaster for MIDI!

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Sun Jan 21, 2018 4:50 pm

Foxie wrote:You probably won't get any improvement in MIDI performance, but you could make it more reliable / less likely to die from ESD. I propose the following mods, but they're completely untested - use at your own risk!


Much appreciated! :D
It might prove useful to do those modifications for the above reasons. But it would be nice to hear from someone more knowledgeable than me having actually performed it and seen that it doesn't have any adverse side-effects that I wouldn't be able to recognize myself.
You mentioned the diodes marked in green should be schottkly types, but which specific schottly diodes?

I have no idea who designed these PCBs but several years ago (2007) I investigated who "EES Moelln" could be (it's printed on all of those C-Lab/Emagic boards such as the Export, Unitor, Combiner etc.) and succeeded in finding Elektronik Entwicklung Service (EES) Möln in Germany. So I contacted them to ask about the possibility of releasing the schematics etc. and actually got a reply. They told me that they had stopped production of those Atari related boards, didn't have any left and didn't know who owned the copyright. I didn't pursue finding out more, but if anyone else is interested, here's their website's "about" page which indeed mentions the Atari ST. There's contact info there too.

Regarding high speed modifications for the ST I believe the ST_ESCC gives two additional serial ports like the Mega STe has while the RSVE only makes the existing modem port go faster. I've got both installed in my STe but never really used the ST_ESCC (the geek in me had a period I just wanted to install every modification I came across) :wink:
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Re: C-Lab Export: unidentified IC

Postby Foxie » Sun Jan 21, 2018 9:08 pm

Fujiyama wrote:You mentioned the diodes marked in green should be schottkly types, but which specific schottly diodes?


Pretty much any schottky diode should work, but you'll probably want to use small signal types rather than high current rectifiers for space reasons. I've used the 1N5817 for various projects before. The main reason to use a schottky diode is to keep the voltage drop low. If you used a non-schottky diode like the 1N4148, there would be a 0.6 volt drop across it. That combines with the 74HC138's low voltage of 0.26V to give an output of 0.86V. That's higher than allowable for a TTL output. In practice it probably won't matter for most MIDI devices since they use an optoisolator. But it might upset devices without an opto like MIDI merge boxes.

I don't think you'll see any actual improvement fitting those diodes though. The main advantage is that it makes it safer when connecting two outputs together. But since you wouldn't normally do that, it's kind of moot. If I were designing the Export from scratch, I'd include the diodes - but a lot of questionable MIDI devices omit them without any ill effect.

Fujiyama wrote:I have no idea who designed these PCBs but several years ago (2007) I investigated who "EES Moelln" could be (it's printed on all of those C-Lab/Emagic boards such as the Export, Unitor, Combiner etc.) and succeeded in finding Elektronik Entwicklung Service (EES) Möln in Germany. So I contacted them to ask about the possibility of releasing the schematics etc. and actually got a reply. They told me that they had stopped production of those Atari related boards, didn't have any left and didn't know who owned the copyright. I didn't pursue finding out more, but if anyone else is interested, here's their website's "about" page which indeed mentions the Atari ST. There's contact info there too.


Interesting indeed! Surprising they're still going in this day and age. Do you have any board photos of the Unitor by any chance? I've seen inside the Log3 before - it wasn't enough to reveal how to program it, but I see they used a microcontroller. I'm guessing the Unitor is similar?

Fujiyama wrote:Regarding high speed modifications for the ST I believe the ST_ESCC gives two additional serial ports like the Mega STe has while the RSVE only makes the existing modem port go faster. I've got both installed in my STe but never really used the ST_ESCC (the geek in me had a period I just wanted to install every modification I came across)


If I can't get my paws on a MegaSTE, I might consider fitting the ST_ESCC to mine. That would allow me to write a driver for those ports. The biggest advantage is that it would also work on the Falcon - which lacks a "standard" serial port. I doubt I'll ever be able to own a Falcon though!

In theory a MegaSTE or ST_ESCC could accommodate three modem port interface devices - and the SCC modem ports can also accept MIDI input. That's a lot of MIDI ports! Then again, even a lowly 1040ST can have a lot of ports hanging off the printer port - if I could just figure out how to write a suitable driver. It's actually easier to write an output-only modem port driver since I can use the Export driver as the basis.

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Mon Jan 22, 2018 9:52 am

Thanks, Foxie. I'll take a note of those diodes.

I don't have any photos of the Unitor, but as I own all of those C-Lab hardware add-ons I could do that soon (send me a PM if I've forgotten about it after a couple of weeks).

I actually have both an STe and a Mega STe. The Mega STe is currently in the midst of being repaired (I believe there are some contact problems with its CPU and/or MonSTer board) while the STe is fully working -but I'm hoping to get a MonSTer for that one too so I can use CF memory cards instead of a hard drive, and also recase the whole thing (19" rack). I never seem to get the time though.
So the ST_ESCC might not be a total waste of money then, if your MIDI interface could be attached and drivers be written. Exciting times :D
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Re: C-Lab Export: unidentified IC

Postby crashman » Mon Jan 22, 2018 2:38 pm

Sent a link to Foxie with Unitor and other midi hardware photos.
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Re: C-Lab Export: unidentified IC

Postby Foxie » Mon Jan 22, 2018 8:08 pm

I've had a look at the Unitor, and it uses a standard off-the-shelf UART chip. It may be possible to clone this. Also, I doubt it's very difficult to program it either since the datasheet is available.

I'm not sure how well Unitor or other cartridge port interfaces perform. The lack of an interrupt is a potential issue, but somehow they avoid dropping data.

There's some questionable design decisions in Unitor, too! Not as shocking as Export, but there doesn't appear to be any protection on the MIDI outputs. Also, the H11L3 optoisolator isn't the best choice since the turn-on current is exactly 5mA - leaving no safety margin. I would advise anyone using Unitor to be very gentle with the MIDI outputs - don't plug them into other outputs and don't static shock them. Fortunately, if you do manage to kill the UART chip, you should be able to find a replacement. Not so with Log3 which uses a custom programmed microcontroller.

I've heard it's possible to extract code from earlier PIC micros by using strange techniques to break the code protection. That would reveal how to program Log3, but it probably wouldn't be enough to clone it. You could clone the MIDI output part, but the main feature of Log3 is the dongle. That would be a lot more difficult to replicate.

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Tue Jan 23, 2018 12:06 pm

Here you go, the Unitor-2.
There's also a Unitor-N (contains a built-in dongle for Notator SL) and Unitor C (likewise, but for Creator SL), but the Unitor-2 needs an actual (Notator or Creator) dongle to be plugged into it.
I don't have access to the -C or -N versions unfortunately, as it would be interesting to see how they differ and what the "internal dongle" consists of.
UPDATE: hold on! I just found out that I do have a Unitor-C :D
So time permitting I'll take some photos of it as well if there's any interest.


PS. I don't know what's up with this forum but I've been having a very hard time uploading the photos. It keeps telling me that the size limit is 500 KB, but regardless I'm not able to upload them. Must be another limitation concerning the pixel size (which isn't mentioned), so I'm inserting smaller photos here and attaching the bigger ones as a ZIP file so you can see the actual IC markings etc.). Sorry about that. I hope they do something about it here.
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Re: C-Lab Export: unidentified IC

Postby Foxie » Tue Jan 23, 2018 3:58 pm

Fujiyama wrote:Here you go, the Unitor-2.


Thanks! It looks extremely similar to the older Unitor, the same chip is responsible for MIDI I/O. They also use a circuit very similar to the Steinberg Midex for SMPTE reading.

I see there's a PAL on the Unitor 2, which I assume is just for address decoding rather than any kind of dongle protection. The older Unitor (I think it was a Unitor C?) seemed to have a big epoxy blob on the board. Probably hiding the PAL containing the dongle protection. They even went to the effort to use lacquer to cover the underside of the PAL to stop you probing the pins. As if a determined hacker wouldn't just scratch through the coating!

What I'm currently trying to figure out is how they're writing to the cartridge port. The old trick uses the address lines as data, and it could be the Unitor uses that trick too. But it looks like the Midex uses another trick I'm not aware of. Somehow, they're able to get the data to appear on the actual data lines without causing a bus error.

Do you happen to know if the Unitor 2 and older Unitor are compatible at the software level?

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Re: C-Lab Export: unidentified IC

Postby czietz » Tue Jan 23, 2018 5:55 pm

Foxie wrote:What I'm currently trying to figure out is how they're writing to the cartridge port. The old trick uses the address lines as data, and it could be the Unitor uses that trick too. But it looks like the Midex uses another trick I'm not aware of. Somehow, they're able to get the data to appear on the actual data lines without causing a bus error.


I'm certainly interested in what you find out in that regard. Back when I designed my software-reflashable ROM cartridge I also pondered about options to write data to the cartridge port and also only came up with using the address lines.

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Wed Jan 24, 2018 12:09 am

Foxie wrote:Do you happen to know if the Unitor 2 and older Unitor are compatible at the software level?


I'm not sure what you mean.
The Unitor-C has the copy-protection hardware for Creator SL built in and only works with Creator SL.
Similarly the Unitor-N intergrates the copy-protection hardware for Notator SL and only works with that software.
Other than that I believe they have the same features, but don't quote me on that. I'll see what I can find out about the Unitor-C I have.

Or maybe I misunderstood your question...
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Re: C-Lab Export: unidentified IC

Postby Foxie » Wed Jan 24, 2018 12:15 am

Fujiyama wrote:The Unitor-C has the copy-protection hardware for Creator SL built in and only works with Creator SL.
Similarly the Unitor-N intergrates the copy-protection hardware for Notator SL and only works with that software.
Other than that I believe they have the same features, but don't quote me on that. I'll see what I can find out about the Unitor-C I have.

Or maybe I misunderstood your question...


I'm wondering if a Unitor 2 with a dongle plugged in is functionally identical to a Unitor-C or Unitor-N? I suppose it might be difficult to tell at the software level whether there are in fact two drivers for Unitor-N/C and Unitor 2? If you take away the dongle part, the two interfaces look very similar inside - but not identical. I'm wondering if there are software-visible differences.

Do you happen to know if the Director program, or the Cubase driver for Unitor works with both Unitor-C/N and Unitor 2 indiscriminately?

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Re: C-Lab Export: unidentified IC

Postby Fujiyama » Thu Jan 25, 2018 1:32 pm

As far as I know the Unitor-2 works exactly as a -C or -N version, but I have no idea what goes on at the software level. I can however tell that there are no drivers to be loaded before the actual Notator or Creator program as I understand it is with Cubase. You just run the Notator or Creator program. Come to think of it, it might have to be run within SoftLink, but don't quote me on that.

From what you're saying above you appear to know what the Unitor -N and -C looks like from the inside, but if not -would you like me to take some photos of the Unitor-N circuit board?

Unfortunately neither of my two Ataris are functional at the moment so I can't test out the C-Lab "Director" program with it, but give me a little while and I'll see what I can do to get one of them working again for testing this out (if not someone else reading beats me to it).

Oh, another thing: I can't remember if it's already been discussed but someone asked me if there's an MROS driver for C-Lab Export which allows it to be used with Cubase on the ST? I heard somewhere that there is such a driver, but I haven't been able to find it anywhere.
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