Emax

Don't lose heart. It looks like Julian may be able to put together a USB to synchronous RS422 port 
adapter which would solve this problem. If not, there various other options. 

In the mean time you still have the Mac itself as a cheap and cheerful solution :) You can buy a lot 
of old Macs for the price of one PC synchronous RS422 adapter!

/Tristan

Sunday, November 23, 2008, 8:05:13 PM, you wrote:

>
>>>here is one that will do what you want, on
configuring correctly and hooking up the right pins. but US$399 makes 
it
more expensive than an emax...
<<<

Oops. I'm getting depressed finding out that my s/h USD50 old Mac is 
equipped with two (!) serial ports capable of what one (!) new USD399 
one can do. And for that 50 dollars the Mac package also includes a 
computer with screen, keyboard, harddisk and floppy drive :-)
(ok, the Quatech will have more *serial* features, but still...)

So I guess the next step is custom building one, e.g. with 
experimental/evaluation boards or from scratch. 
Not my piece of cake...

I guess experimenting with the CTS/RTS signals also does not make 
sense anymore, right ? I thought it could be a way to keep the 
drifting under control... I guess not... 
And I'm still a bit afraid that it could damage my PC RS422 port 
since the RTS/CTS pins are expecting either positive or negative 
voltages but not a mixture of them. Or are those ports typically 
protected against this "abuse" ?

In the meanwhile I currently have an "almost perfect" setup in my 
studio: One Mac Classic, with an external ZIP drive and CDROM drive, 
is connected to both the Emax (printer port) and the Emulator II 
(modem port).
The only problem is that I can't run both Sound Designer for EII and 
Sound Designer for Emax at the same time due to memory restrictions. 
I was hoping my Powerbook 180 - which has also two serial ports - 
would be the solution, but this machine requires AppleTalk to be ON 
for communicating with the EII, which unfortunately disables the 
Printer port for the Emax.
Well... we're not living in a perfect world :-)
Maybe I will give each of the instruments its own Mac...

...until we have the ultimate PC solution of course (with 2 or more 
RS422 ports on it)

///E-Synthesist

--- In emax@yahoogroups.com, mr julian <jujulilianan@...> wrote:
>
> 
> those RTS(ready to send) and CTS(clear to send) +/-(differential 
pairs) 
> are two separate signals. neither of which is a clock. They're 
> handshaking signals, used to signal and control the data flow 
between 2 
> devices.
> 
> So if that's what you have on your RS422 ports, but nothing labeled 
> something like "clock in" or "clock I/O" you don't have any 
synchronous 
> comms compatible RS422.
> 
> It appears that without synchronous communication, the emax won't 
> work... after first posting about what you might need, I went and 
got 
> back my copy of the emax service manual, and it shows very clearly 
a 
> 500k signal going from the emax to the computer.
> 
> the issue here is, that with a different 500k clock on the 
receiver, you 
> can have the units basically appear to work. but no two 500k clocks 
are 
> exactly the same frequency - and here's the sticky bit - the emax 
needs 
> a long sustained transfer... so even if they start off in step, 
> eventually the timing of the devices moves so the receiver is out 
of 
> time with the transmitter, and you get a data error...sound 
familiar? 
> and because it appears that the emax kills a whole transfer on a 
data 
> error, once that happens, it's all over. if the EII has a more 
robust 
> protocol, it could run without synchronisation, and just re-
transmit a 
> failed packet whenever inevitable clock differences cause a problem.
> 
> I thought I had sent a link earlier to a card that would work, but 
on 
> double checking I hadn't.... must have looked it up when i was 
> investigation the PC side of synchronous RS422, but not sent the 
> link..... anyway - here is one that will do what you want, on 
> configuring correctly and hooking up the right pins. but US$399 
makes it 
> more expensive than an emax...
> http://www.quatech.com/catalog/rs422s_pcmcia.php
> I've just spent an hour or two looking around, and haven't found 
much 
> that will do what you need for a lot cheaper.....
> :-(
> 
> 
> Anyway.. I'm spending another few hours evaluating something else 
now.
> 
> I've had one of these sitting around at home for a while
> http://www.atmel.com/dyn/products/tools_card.asp?tool_id=3879
> 
> And its a cold windy sunday afternoon here.
> I've been meaning to have a go at playing with that eval board with 
this 
> software for a while.
> http://www.fourwalledcubicle.com/MyUSB.php
> 
> I'm not sure if it's an option yet, but this could be the basis of 
a 
> solution for the problem. Especially if the issue isn't packet-
packet 
> timing, but is simply just an issue with serial data 
synchronisation...
> 
> 
> 
> 
> 
> esynthesist wrote:
> 
> >You made be thinking again.
> >
> >When I started my experiments I asked for some advice on serial 
> >communication on a Dutch electronics internet group. One of my 
> >questions was whether the 4 handshake signals on the standard 
RS422 
> >(RTS+, RTS-, CTS+, CTS-) can be compared in some way to the HSKi 
and 
> >HSKo signals of the Mac serial port. Specifically I was also 
asking 
> >what to do with the + and - signals, given the fact that the 
> >Emax/Emulator sends a clock signal which is going + and - on the 
same 
> >line, while the RS422 expects seperated opposite signals.
> >I also asked if an independent clock in the PC RS422, running at 
> >500kbaud would be sufficient, instead of external clocking. 
> >At the end the experts on this group confirmed that an independent 
> >clock should be OK, even if it's not clocking exactly at the same 
> >speed of the Emulator II and that phasing problems can be ignored.
> >One of the arguments they based their conclusion on was that the 
> >Emulator II communication protocol is *asynchronous* (as also 
stated 
> >in the technical documents of the EII).
> >Were they wrong ?
> >
> >And do you know the most appropriate wiring between the 4 
> >RS422 "clock" pins and the single clock pin of the Emax/Emulator 
II ?
> >
> >Or do I understand you completely wrong, and are those "external 
> >clockable RS422 devices for the PC" not using these 4 signals but 
> >even another one ?
> >
> >By the way: what exact link to which RS422 device are you talking 
> >about ? I reviewed the messages but didn't find a direct link ?
> >
> >///E-Synthesist
> >
> > 
> >
>