Support for 16/32 Serial ports (RS232)

[Ian]

Hi,

 

I need to control up to 32 serial port devices (RS232) using Labview.

Can any body recommend a product that will do this?

 

I have been looking at Terminal Servers (e.g. http://www.perle.com/products/Terminal-Server.shtml)

Does anybody know if I can use this device with Labview to access each RS232 device.(NB: I can currently access each device using TeraTerm).  The recommended retail price for a 16port unit is £800.

Can anybody suggest a cheaper solution?

 

Thanks in advance.

Cheers

Ian

[Wire Warrior]

NI offers this 16-port serial card to plugin to your computer. http://sine.ni.com/nips/cds/view/p/lang/en/nid/207740

Probably be your best solution. Details below.

NI PCIe-8430/16 (RS232) High-Performance, 16-Port RS232 Interface for PCI Express

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• Compatible with Windows and LabVIEW Real-Time OSs
• Flexible standard and nonstandard baud rates from 2 baud to 1,000,000 baud
• Better than 0.015 percent accuracy for standard baud rates and 0.5 percent for nonstandard rates
• High-speed DMA interface and 128 B transmit and receive FIFOs minimize CPU overhead
• Includes two 8-port breakout cables (68-pin VHDCI to eight D-Sub 9-pin male ports)
• NI-Serial driver includes free NI-VISA API for easy programming
  

[Phillip Brooks]

When I see that many ports needed, I gravitate towards the terminal server option. You will reach a point when you need multiple computer access to the ports or want to locate the computer(s) an extended distance from the UUTs. 

 

Yes, you could share the 8430 ports remotely through VISA, but I'll take a device that is designed to be left on for 24/7 for years over a Windoze / Antivirus / desktop PC (HD and RAM failures) combo that inevitably suffers a BSOD in the middle of a critical high utilization run.

 

I've just switched out some very old Equinox terminal servers with the Perle IOLAN STS16 and they are very nice. I use both telnet and socket based connections to my UUTs without a problem. The price for either solution seems to be about the same.

[David Boyd]

I've used Digi devices for years, with few issues.  Biggest system to date has four Etherlite 160's (total of 64 ports); sixty ports are tied to UUTs spewing 6400 char/sec each, all of which is digested by my LabVIEW application.  The other four ports are used for instrumentation, doing query/response (a few dozen chars per message, as fast as the instrument responds).

 

These terminal servers are setup to use the Digi RealPort driver, which provides standard Windows comm API, so VISA treats them like local asynch serial.  When you get up to this level of activity, with array-launched VI clones, and lots of queue/notifier/event structure support, you have to be pretty careful about the details.  Seemingly minor changes to cloned code, reentrancy settings, execution system assignment, etc can mean the difference between a working app and a quivering heap of unresponsive code.

 

Dave

[hooovahh]

Seemingly minor changes....can mean the difference between a working app and a quivering heap of unresponsive code.

 

Dave

I like this.  I'm going to steal this quote.

Edited April 19, 2013 by hooovahh

[Ian]

Thank you to everyone, some very useful advice.

[FixedWire]

We've used Quadtech 4 port devices for USB in the field and they work fine. Just be very careful that there is not too much data coming down the pipe going through a low throughput USB port. This will cause your CPU to work very hard since the controller can't handle it.

http://quatech.com/catalog/rs232_sds.php

[Mads]

We use terminal servers for this all the time. Moxa, Advantech, Digi and Westermo.

 

The virtual serial port drivers that come with these devices never (the ones from Digi might be the exception)  handle network connection issues gracefully. If the network goes down for example, the drivers will freeze - and this can cause VISA to freeze or crash.

 

However, if you use raw TCP/IP connections and write your own client (VISA has in-built functionality for this as well...I'm not sure if that's robust though), then you can make all of them work nicely.