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I have a module that is usually bundled with a master module, which we now want to use unbundled. The module uses an RS-485 interface. The problem is, by default, the module runs at 1.25 Megabaud, which is not one of the "standard" speeds that most integrated PC serial ports run at.

For my own uses, I can whip up a relay system using some microcontroller demo boards I have lying around, but we also have a desire to make this usable for people without mad embedded skills.

So, does anybody have experience with, e.g. PCI-to-serial cards that can run this fast? It's fine if we end up with a fast RS-232 card that then goes to an RS-485 converter, although it would also be cool if they actually had a PCI-to-RS485 card that worked standalone.

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reopening on the basis of meta.superuser.com/questions/2324/… –  Jeff Atwood Aug 2 '11 at 22:46
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4 Answers

up vote 4 down vote accepted

My typical go-to place for stuff like this, B&B Electronics, only has cards that go up to 921 kbaud.

If you can spend the big bucks, National Instruments has a card that can do any arbitrary rate from 57 baud to 3 Mbaud. It seems like Win7 drivers are available on NI's site; I don't have any first-hand experience with NI's interface cards, but they aren't exactly a no-name brand.

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The NI card appears to be what I'm looking for. Thanks! –  Sam Skuce Nov 1 '10 at 19:38
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I've used DIGI (http://www.digi.com/) equipment in the past for our serial loops that we were hanging terminals off of. You might find something of theirs that fits your need.

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I admit I am not too familiar with serial ports and connections, however, a quick look on newegg.com returns a couple of options that may work for you; specifically the SYBA branded ones.

EDIT: the SYBA ones are PCIe, which may not be compatible with your setup.

EDIT 2: a full search of Newegg's PCI - Serial collection here reveals only one card that claims to offer speeds exceeding 1 Megabyte with RS422/485 support

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Thanks Xantec, unfortunately, looking at Newegg's customer reviews, the Syba products seem to have a bad reputation. The card you linked to doesn't have signed drivers for Windows 7, and another I found apparently causes Windows 7 / Vista to crash and reboot spontaneously, and Syba's response is that the user should turn off ACPI in BIOS settings, which is not desirable if I'm going to end up supporting this for our less technical users. –  Sam Skuce Nov 1 '10 at 17:08
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Starech makes a number of serial cards at reasonable prices. This one is at their higher end Serial Combo Card As mentioned, Digi has some great products as well.

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FTA: 921.6Kbps maximum baud rate per port –  Nick T Nov 1 '10 at 17:48
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