#UVW-1800 and RS422
10 messages in this thread
I've just obtained a Sony UVW-1800 and a UVW-1600. I'm trying to interface
these to a PC using the RS-422 interface and I'm having problems. The doc for
the 9 pin connector on the UVW's contains lines called "Receive Common" and
"Transmit Common". The standard 25 pin RS-422 interface (EIA definition)
doesn't include anything that obviously maps to these two lines. I've tried
leaving these two lines unconnected but the UVW's don't respond (ACK, NAK or
anything else) to any commands I send from the PC.
What needs to be done with these lines to make this work?
I'm assuming that this interface is running 1 start bit, 8 data, odd parity and
1 stop bit at 38.4 kbs. Is this correct.
Any suggestions anyone has would be greatly apprciated.
Tnx
Raymond Raw St. Agatha ON Can
Hi Raymond.
I'm no expert on RS-422, so I'm about to offer some guesses. (I use a UVW-1800
as a record deck with a FAST Video Machine – this connects with a
straight-through 9 pin to the UVW at one end and the VM at the other).
I believe that Sony adopted the RS-422 electrical characteristics (though I'm
not sure in their entirety). However, Sony developed its own protocols for
communications to and from their tape decks. Many other manufacturer's have
since adopted the Sony standards.
I personally have not seen anything other than 9-pin in the video world
(perhaps others have), so I am not sure how to advise you on the mapping. If
you are trying to control the decks from a commercial editing package (as
opposed to having written the software yourself)m I would recommend you contact
the manufacturer of the software for advice.
You also don't mention whether the PC port you are using is a general purpose
RS-232 port, or is designed as a RS-422 port. My understanding is (and I'm not
sure it is correct) that RS-422 requires a special port.
Probably none of this helps, but I thought I'd try anyway. Good luck!
Bob
Thanks Robert. Every little bit of info helps. In my case I have a true
RS-422 card in the PC. I'm trying to write (actually, its 90% written) a
simple cuts only editor to control the decks. It's a contract programme for a
very small local editing shop that has a very specific need. The programming
part if fairly straight forward. I have a copy of the Sony control protocols
and they're fairly straight forward to use. My problem seems to be with the
electrical interface to the decks. From the doc I have, everything suggests
that it should be working but the decks don't respond in any way to the
commands I send.
I have a VM also for my own use but no Studio Control box so I can't connect
these decks to the VM to try them. It's a great product, I love it.
Unfortunately, its a little costly, complicated and grossly over kill for my
clients needs.
Raymond Raw St. Agatha ON Can
Raymond,
If you have an RS422 card already, you merely need to make up a custom cable
that ties it to the VTR. You can pretty much bet that the cable will NOT be a
pin-for-pin cable.
Connect the card's transmit plus (Tx+) to the VTR's receive plus (Rx+), and Tx-
to Rx-. For the return path, it's the same Tx+ to Rx+, and Tx- to Rx-. The
commons can be tied together to the signal ground of your RS422 card. Chassis
ground can be tied to the cable's shield (for short runs, don't worry about
it).
You CAN use most any PC COMM port IF you get an RS232-422 adapter. Addenda
Electronics (408 372 6192) sells them cheap. They look like 9-pin to 9-pin
gender changers. Plug and go.
Bruce
Ray,
There have been some good suggestions (I'd check the cable closely with an
Ohmeter or continuity tester) but if you stillhave a problems, pop down to
Radio Shack (or equivalent) and get a break out box. It will have jumpers and
LEDs on each pin and you can see if there are any control lines high or low.
Compare it to a working setup. If that doesn't help, get your hands on a
Protocol Analyzer. It will tell you the digits sent, show control line
transitions, clock pulses, baud rates, etc. They're kind of expensive to buy
but can be rented fairly cheap for a short time. It will probably tell you
within a few minutes what's going on.
Jim
Thanks to all that have offered suggestions. Although I haven't got the
interface working yet, I've pretty much narrowed it down to a bad baud rate
clock on my RS-422 board. I measured it with a little timing routine I wrote
and found my baud rate to be out of spec by 52% at a baud rate of 38.4kbs. I
can't blame the decks for not responding to that kind of error. Right now I'm
looking for a local store where I can buy a new crystal for the board.
I also dicovered that the board I have is really RS-423 not RS-422 although the
two standards are compatible. My testing also leads me to believe that the
UVW-1800 interface is infact RS-423 also and not 422 as documented. Not that
this matters any.
Raymond Raw St. Agatha ON Can
"and found my baud rate to be out of spec by 52% at a baud rate of 38.4kbs."
Ray,
Wow! That's quite a bit. I think I'd be on the phone to the vendor. Have you
tried changing the baud rate on one end by 52% to "fool" the equipment into
working <G>?
I haven't looked into the (supposed) RS-422 control interfaces but I guess I
wouldn't be supprised the find some manufacturers going cheap, skipping a wire
or two and turning a balanced standard into the unbalanced version (422 and 423
being only electrical standards, not protocol standards). Probably will work
well over short distances but the balanced standard is the only way to go in an
electrically noisy environment such as a large studio or edit suite.
Good luck, sounds like you got a handle on it,
Jim
Raymond,
The transmit common and receive common that you mention, are they pins two
and three or something else? As someone else has stated, all you should
really need is three-pins, tx-rx (normally pins 2-3), rx-tx (normally pins
3-2), and ground (normally pin 7). This is commonly known as a null-modem
cable or a serial printer cable.
The other thing I am not sure about is your baud rate. 38,400 sounds
awful high for a VTR. You might try 9600 or at least verify from the
manual/jumper settings what exactly the deck is set to.
-John
PMFJI, but RS422 uses two wires in each direction. With ground, a minimal
connection is five wires: Tx+, Tx-, Rx+, Rx-, and Ground. The serial data rate
is indeed standardized at 38.4 kBaud.
Thanks for fixing me up there, Bruce.
-John