[time-nuts] USB problems and solutions - Some what Off Topic

Tom Van Baak tvb at LeapSecond.com
Sat May 30 01:21:42 EDT 2015


> I'm coming to time-nuts because I remember that at least one member had a
> very large number of adapters on one computer, so I'm hoping to find some
> help. I don't generally seem to have trouble with other USB devices, just
> the serial adapters.

Cash,

True, it's somewhat off-topic but a lot of us collect data from instruments and so the issue of serial ports and USB comes up from time to time. I have run up to 40 serial ports on a Windows laptop using a combination of USB 7-port hubs and EdgePort 8-1 serial/USB adapters. It can work perfectly. Some personal comments:

- Use FTDI serial/USB adapters. They are very solid on Windows. Avoid SI Labs and Prolific adapters. My favorites these days come from Sparkfun and Adafruit (serial, 3.3/5 volt) and Parallax (serial, true RS232). Avoid the fake-FTDI adapters you see on eBay.

- Use Digi (Inside Out Networks) Edgeport serial/USB adapters if you want 4-1 or 8-1 or even 16-1 serial ports. I've never had trouble with Edgeport software. These are higher priced per box but lower on a per-port basis. They are available and cheap on eBay, since DA9 (DB9) serial ports have fallen out of fashion.

- Both FTDI and Edgeport include excellent configuration utilities. For example, you can delete COM ports or change COM port numbers on the fly. Some programs won't let you use a large com port number. In a few seconds you can redefine a FTDI or Edgeport adapter to be COM2 or COM3, etc.

- By default the FTDI and Edgeport serial/USB adapters will retain their COM port number(s), which is handy most of the time. For example, I have an Edgeport/8 with #2 written on it. Every time I plug it in, I COM21 to COM28 show up. Similar ones have labels #3 and #4, etc. So I always have serial ports if I need them.

- If you play with serial ports a lot it's nice to know what the port numbers are when you plug adapters in and out. Under http://leapsecond.com/tools/ see the coms.exe (coms.c) tool which displays and monitors for changes in the list of com ports. ^C to exit. 

- The web also has lots of advice on how to clean up unused COM ports on Windows. Personally I tend not to bother, because the config utilities allow you to change any port you want to use.

- The web has lots of good (and bad) advice to avoid the serial ball mouse problem should you ever run into that.

- If you want Windows serial logging and timestamp software contact me off-list.

Thanks,
/tvb



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