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Al Williams

Dr. Dobb's Bloggers

Legacy USB

May 24, 2010

RS232 is on the way out. It kind of makes me sad. I started my career working on serial multiport switches and it seems like everywhere I've been there's been some kind of serial port around.

But my motherboard only has one serial port and my next one will probably have none. None of my laptops have one. Of course, I cheat and have a bunch of USB to serial adapters including some Edgeports boxes that give me 8 serial ports in a box. Even I don't really need 8 serial ports.

I have often thought of building an RS232 adapter that fits in a MAX232 socket since those are so ubiquitous now days. Its hard to fit things in that little space though (I've tried). You don't need much. Both FTDI and Silicon Labs have tiny single chip solutions for USB to serial.

And by coincidence, I just noticed two offerings, one using each brand of chip, that build the adapter into a fake DB-9 connector. In theory, you could replace a DB-9 right angle connector with one of these and turn your legacy RS-232 device into a USB device.

There are two downsides. First, you have to retain the existing RS232 components because the adapters put out "true" RS232. Second, is the price is a bit much. Both boards are around US$25.

The one based on the Silab 2102 is from Copeland. The other is available directly from FTDI. If you've tried either of these, leave a comment and let me know how it worked for you.

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