Chief Delphi - Dell laptop serial port

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- Programming (http://www.chiefdelphi.com/forums/forumdisplay.php?f=51)

- - Dell laptop serial port (http://www.chiefdelphi.com/forums/showthread.php?t=49624)

Dave Flowerday

26-10-2006 16:37

Re: Dell laptop serial port

Quote:

Originally Posted by Astronouth7303

It's notable that the highest common serial speed (115200) is faster than USB 1.0.

You may want to recheck your numbers. USB 1.0 (aka "low speed USB") is 1.5Mbps, quite a bit more than 115,200bps used for serial. At any rate, nearly all devices support at least USB 1.1 (aka "full speed USB") which is 12Mbps. USB 2.0 ("high speed") is 480Mbps.

Astronouth7303

26-10-2006 17:06

Re: Dell laptop serial port

Quote:

Originally Posted by Dave Flowerday

Your right, my bad. :o

USB 1.0 "low speed" comes out to 1500000 bits/second. This would include any encoding, bit shuffling, USB overhead, etc.

Serial comes out to 92160 data bits/s (assuming 8N1 configuration, which is fairly standard; this is found by multiplying the baud rate by 80%=0.8).

Also, USB is half-duplex query-based. USB is succebtable to congestion (that is, a lot of devices on the same hub will slow down bandwidth). Every USB packet is at least 22 bytes long (for the header).

Serial is simple; the Tx and Rx lines just transmit data at the baud. So there is no overhead (handshaking and transmission control is often done with secondary lines).

AV_guy007

26-10-2006 18:19

Re: Dell laptop serial port

about serial being faster than USB. i don't have the facts to back this up but a Friend and i were programing vex bots over the summer. i had the standard vex USB to serial adapter plugged into a USB 1.1 port and my Friend was just using a standard serial cable. i noticed that his code loaded at least 5 times faster than mine every time. :ahh:

Cai ZhongHan

26-10-2006 22:32

Re: Dell laptop serial port

Quote:

Originally Posted by Eldarion

Seeing as the port replicator interfaces directly to the mainboard of the laptop over a high-speed bus, chances are it would be more like adding a daughterboard with a serial port and it might even be assigned IRQs and I/O addresses by the laptop's BIOS, in which case it should be indistinguishable from a normal serial port.

Just my $0.02. :)

Yes, that's the case with my IBM Thinkpad.
I/O Range:03F8-03FF
IRQ: 04
Location: on Intel(R) 82801DBM LPC Interface Controller - 24CC

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