John Peter Loh wrote:
I saw a tutorial on testing serial ports with an RS-232 Break Out Box
and echoing a chunk of text to /dev/ttyS0.
/dev/ttyS0 is the first pin of the serial port, right?
If by 'first pin' you mean the first serial port(usually labled 'A') at
the back of your PC,
then the answer is 'yes'.
What should I echo just to have one pin light up if I have a LED
connected to it?
If I understood you correctly, you want to echo a text file containing
some text in it.
For example,
# cat myfile.txt > /dev/ttyS0
You also probably need to know the pin configurations.
There are two cabling configurations. One a DB25 and the other is a DB9.
The numbers being the number of pins in your RS-232 port. Chances are
you have a DB9.
In the old days of computing, we simply cross connect CN2 (Receive Data) to
CN3 (Transmit Data) and get the CN5 (Ground) connected. Ergo we will get
a transmission going. But with new computers, your devices will probably
wait
forever if this all you do.
So, you need to do some pin looping not cross connecting.
Loop CN1, CN6, and CN4.
Loop CN7 and CN8.
CN9 is not connected.
Symbols:
CN1 - CD
CN2 - Rx
CN3 - Tx
CN4 - DTR
CN5 - Ground
CN6 - DSR
CN7 - RTS
CN8 - CTS
CN9 - Ring
Did I get the right concept? Is there a site/page for the signalling?
Disclaimer: I bear no responsibility for the suggestions I offer here.
It is your responsibility to ensure you do right. Do not proceed if
you are unsure.
O Plameras
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