×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

long distance high speed serial link

long distance high speed serial link

long distance high speed serial link

(OP)
I'm looking into implementing a 16 Mbps (megabit/sec) serial link (one Tx, one Rx) that has to run at least 15 meters.  Any suggestions?  

Last time I checked this was beyond the capability of RS-422; has anybody made any improvements in drivers or receivers, or do those same old laws of physics apply?  

I want a 'real-time' channel, so I'm trying to avoid something like Ethernet (100M, 1G, etc.) where I would have to re-sync the data in the receiver.  Is a simple point-to-point solution available, or do I have to get more sophisticated?  

Thanks,
 
John D
 

RE: long distance high speed serial link

(OP)
I've used LVDS for short links (LCD displays), but didn't know it had long range capabilities.  I'll look into M-LVDS and B-LVDS.  

Everything in that paper looks good until I got to Figure 9.20 on p. 96; there they show RS-485 good for 40 Mbps on a 70 meter cable and 400 kbps on a 700 meter cable.  Where did they get that data?  That shows RS-485 could work for my application, but I've typically seen RS-485 spec'd at 1 Mbps or 1 km cables, but those are mutually exclusive specs.  

Anybody have experience with M-LVDS or B-LVDS?  Or 40 Mbps RS-485?  

John D


 

RE: long distance high speed serial link

Profibus-DP is RS-485 using special wire. It can go up to 12 Mbps at 300 ft (100 mtrs). So I would say that RS-485 will do 16 Mbps at 15 ft. You will need to have a matched, properly terminated cable and high speed RS-485 drivers. I believe that TI makes such chips.

RE: long distance high speed serial link

Yes RS485 can get to 16Mbps.  You do want to use 'good' cable.

There are lots of other options, like you could run multiple lines too. You could get a four channel transceiver and feed the data out in nibbles. Or, run two 4 channel chips and dump out 8 bits at a whack, which might be easier or much more efficient to implement.  That would allow crap wire and 2Mbps speeds.

http://cds.linear.com/docs/Datasheet/485fh.pdf

52Mbps.   

Keith Cress
kcress - http://www.flaminsystems.com

RE: long distance high speed serial link

(OP)
Thanks all, I'll check these out.  It looks like RS-485 has come a long way over the years (thanks to the cable manufacturers).  

At this point I'll keep exploring a single channel to keep the weight and size down on my cabling.  

John D
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources