Emax

OK, other members seem to confirm that the additional 4 holes are on 
the PCB already :-)

About my RS422 experiments: in fact I'm able to communicate with the 
EII, it's just that the communication is a little bit unreliable when 
receiving data from the EII, and *very* unreliable when transmitting 
data to the EII. In my opinion the only two possible causes can be:
- problem in voltage level
- problem with timings.
Since receiving data goes quite well (18-20 seconds including re-
handshakes compared to the 11 seconds without re-handshakes on a Mac) 
I don't think there are timing problems. Both the EII port and the 
USB/RS422 converter are clocked at 500kbaud - note I had to buy a 
specific USB/RS422 converter since the standard ones are not capable 
of being clocked at 500kbaud. But still this is a different situation 
compared with the Mac since the Mac's serial port is externally 
clocked by the EII's clock, which guarantees of course that they are 
synced. This external clocking is simply not available on RS422 PC 
ports.
My guess however is that the USB/RS422 transmit signal is too low for 
the EII (or more particularly: the differential transmit level is too 
low). I'm pretty convinced about this because "getting a bank from 
EII" goes very well while "sending a bank to EII" is a disaster. 
Sending data from PC to EII requires of course a lot more bytes to be 
sent than receiving data, and my experiments show that the stream of 
data seems to be partly "destroyed" when it arrives at the EII (the 
EII answers with a NACK or keeps waiting for more data because it 
thinks not all data have been received yet).
However I don't have a digital scope to confirm this... but I'm 
really thinking about buying one now ! Now even when the scope 
confirms my thoughts, the next question is what I should do to solve 
the problem. Building custom hardware seems not very attractive from 
the perspective of potential EII users I guess...

Mmmm... interesting but frustrating... just like upgrading the Emax 
with SCSI :-)

PS: I'm still waiting for a reply from my synth repair guy concerning 
the SCSI upgrade.

///E-Synthesist




--- In emax@yahoogroups.com, Ted Summers <djtbs1@...> wrote:
>
> Thanks for the encouragement.  From my understanding, the holes 
are  
> already there for the socket.....
> 
>  >> In fact I think this expense problem is part of and compensated 
by
> the challenge/kick/hobby/appreciation...isn't it ?
> True.....
> 
> On your project---
> 
> Regarding the USB converters- are you working on Mac or Laptop 
that  
> has no serial? The serial is RS422, at 500kilobits (not bytes) per  
> second, according to the service manual. it also says the RS422 is  
> using differential mode.
> Here is a web page discussing that:
> http://www.lammertbies.nl/comm/info/RS-422.html
> 
> Maybe you already know about these things, but just in case.....
> 
> I would think the biggest challenge there would be timing between 
USB  
> and the RS422, and I believe RS422 uses different signal levels. 
It  
> may be that the USB is using too low of signal levels....
> 
> just a couple of thoughts.
> 
> Regards,
> Ted
> 
> 
> 
> On Oct 25, 2008, at 9:36 AM, esynthesist wrote:
> 
> I think quite some Emax users really appreciate your efforts !
> 
> So do I, and I didn't even buy your SCSI kit (yet) :-)
> 
> In fact I was very enthusiastic when I read about your SCSI kit and 
I
> was even more thrilled when I discovered my Emax SE keyboard had a
> Rev2 board.
> But... my enthusiasm kind of disappeared when I started reading the
> SCSI Upgrade instructions. My headache reached a climax when I read
> that a 24-pin IC socket should be removed and replaced by an 28-pin
> socket (what about the PCB holes for the 4 additional sockets ??)
> So as other members already mentioned: the problem is probably not
> the price (which is really fair) but the technological challenge and
> the risk to destroy a perfectly working Emax.
> Personally I'm thinking about outsourcing this upgrade job to my
> synth repair guy but I have to ask him a price estimation first.
> 
> Of course this kind of upgrade/rev.engineering activities take a lot
> of time and may also require some "personal cash" investment.
> E.g. for developing EMXP and making sure everything works fine I had
> to do quite some investments. At the beginning I thought that having
> an EMAX SE, an EMAX-II, an EII+, and an EIIIXS would be sufficient
> for making sure that the software works on all samplers of those Emu
> families.
> But it seemed I had to buy an Emax Plus and a "real" EIII also,
> machines I didn't need otherwise. Especially the EIII was very
> expensive and I'm still not really using it - it's just sitting 
there
> for test purposes of EMXP. (true, I can sell them again when I stop
> developing this software)
> Another example: for the past few weeks I was trying to add serial
> communication to EMXP for the Emax and EII. But to come to the
> conclusion that this will probably not be possible, I first had to
> buy two USB-RS422 converters and one USB-RS232 converter.
> I'm glad I didn't buy a 1000+ EUR digital oscilloscope yet :-)
> 
> But I don't really care about these expenses, fortunately I don't
> have a wife :-)
> In fact I think this expense problem is part of and compensated by
> the challenge/kick/hobby/appreciation...isn't it ?
> The fact that we are helping some Emu fans out there and that they
> really appreciate our efforts could be our main driver/objective.
> 
> Many thanks for the efforts and I'll probably send you an order in
> the coming days/weeks !
> 
> ///E-Synthesist
> 
> --- In emax@yahoogroups.com, "Ted Summers" <djtbs1@> wrote:
>  >
>  > Thanks for your words of encouragement. $2500- wow. My wife 
freaked
> when she
>  > realized I had spent the $900 (although she somewhat chilled out
> when I told
>  > her that I had made some of it back)---- I couldn't imagine the
> amount of
>  > your project .... I hope people start coming through for you as
> well.
>  >
>  > It is all very easy for people to say it could be done cheaper. I
> think we
>  > both know it isn't all as easy as it sounds. You never really 
know
> what it
>  > is gonna take until you get into it. And once you get into it, 
you
> feel like
>  > you wasted your money / time if you just drop your effort too....
> catch 22.
>  >
>  > Best of Luck!
>  >
>  > Regards,
>  > Ted
>  >
>  >
>  > [Non-text portions of this message have been removed]
>  >
> 
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>