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Frequently Asked Questions

A Brief Introduction to USB and Serial Ports

By Dana Cartwright, author of WeaveMaker software

The question of 'ports' on modern computers is complicated. So bear with me as I go through this explanation. I'm writing this from the perspective of WeaveMaker and Macintoshes, but it's the same for all software, and increasingly Windows computers have these issues. I'll try to make this as generic as possible!

Older computers (both Mac and Windows) came with built-in serial ports. On the Mac there were two, usually called 'modem' and 'printer'. Similarly, Windows computers almost always had a serial port, called COM1 (and if there were multiple such ports, the others were COM2, COM3, etc). The problem with these older serial ports is that their design literally pre-dated computers. They were engineered back in the days of real Teletypes, the kind that were used to send real telegrams, delivered by a person wearing a uniform, complete with hat. These older serial ports were slow, and the way they worked wasn't compatible with modern computer electronics, and so they required expensive chips inside the computer to accommodate them.

To solve this problem, the Universal Serial Bus (USB) port was created. (Confusingly, this name contains the word 'serial', which is also used to describe the older ports. Sorry, I wasn't responsible for naming these things!). USB is fast, completely compatible with modern computer electronics, and is therefore relatively inexpensive. USB is great for hooking up printers, extra disk drives, cameras, scanners, fax machines, music keyboards; it really is universal. So that's good.

Problem is, all the computer dobby boxes (including the AVL Compu-Dobby) on the market today were engineered to use the older, slower serial ports. To get a modern computer to talk to a dobby box, you need a USB-to-serial adaptor. This lets a USB port act like the older serial ports.

Now, this creates all kinds of headaches for weaving software:


So what's the bottom line? Modern weaving software has to do the best it can to examine your computer and find your USB-to-serial driver and associated hardware. And as I've indicated, there are many ways to do this, and many ways in which it can go wrong. The software then has to issue error messages as appropriate, to try to help you resolve the problem. This is not easy!!! So, the bottom line is patience, patience, patience.