Serial port question

Feb 16, 2004 5 Replies
C

I've got a very simple application involving a PC transmitting (only) to a display over RS232. In theory only two wires are required Tx and Gnd as the display can "keep up" with whatever data rate the PC can produce. I'm using a test program that has the following handshake options "None, XON/XOFF, Hardware etc". I'm assuming that if I select "none" then the test program won't use handshaking but what about the UART itself?



Does the UART in a PC need hardware handshake lines pulled to a particular state in order to transmit?


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M

the

using

No, in my experiance it will work with all the other lines floating.

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N

the

using

The protocols (both hardware and software) that govern PC serial communications are *all* dictated by the software. The UARTs themselves are just reporters of electrical facts.

Norm

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J

no it does not. but it may need the DSR line pulled up ?. that is just a guess.

CWatters wrote:

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R

------------ If you bit-bang the port IO itself, no, but if you use the BIOS, then yes, you'll need the DSR and CTS to be fooled because the BIOS will require it.

-Steve

-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!! http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
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C

Thanks for all the replies. I finally figured out that the display I was driving needed a higher voltage power supply.

If anyone else needs a simple app to test a serial port device then I recommend "Serial Device Tester" by Hack Consulting at

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