On Fri, 2007-03-16 at 15:11 -0700, David Brodbeck wrote:
Carlos E. R. wrote:
Then you will have to get port pci cards, but if you are using portables, you are out of luck. pcmcia then?
I would be shocked if no one makes a USB device with some input and output terminals for this kind of basic "bit-banging" I/O. PC Cards with RS-232 ports or parallel ports also still exist, although they probably aren't cheap.
The USB protocol is not instantaneous. It is packet based. A packet needs to get across the interface, be decoded, find its way up the USB driver chain to the client app. The serial port, OTOH, provides an interrupt direct into one driver without any hardware packeting. It is measurably quicker.
Basically, where you used to get one or two ports for free on each machine that you could use for this kind of basic I/O, in the future you're going to have to pay for them.
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