long distance high speed serial link

[zappedagain]

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

 

[IRstuff]

Have you considered LVDS?

http://www.national.com/appinfo/lvds/files/National_LVDS_Owners_Manual_4th_Edition_2008.pdf

Note that you'll probably need to use higher-end cabling

TTFN

FAQ731-376

 

[zappedagain]

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

 

[djs]

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.

 

[itsmoked]

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

 

[zappedagain]

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