How to make a RS-232 Activity LED circuit?

[Bob Business]

Hello,
I have a project that uses a 2 wire connection via RS-232 / DB9 serial
to program it, but nothing is happening, so I thought I could use a
circuit that connects and displays activity via 2 dual color LEDs.
Since I am a programmer by trade, I have no idea how to do this, so I
was wondering if anyone had any plans or ideas. Note that RS does
carry a product like this for $15, but it is DB25, and has lights for
7 data lines. I only need 2.
Thanks,
Bob

 

[petrus bitbyter]

"Bob Business" <bob@shoptalkforums.com> schreef in bericht
news:3e5f9f92.0309141254.49517c0b@posting.google.com...

Hello,
I have a project that uses a 2 wire connection via RS-232 / DB9 serial
to program it, but nothing is happening, so I thought I could use a
circuit that connects and displays activity via 2 dual color LEDs.
Since I am a programmer by trade, I have no idea how to do this, so I
was wondering if anyone had any plans or ideas. Note that RS does
carry a product like this for $15, but it is DB25, and has lights for
7 data lines. I only need 2.
Thanks,
Bob

Bob,

Take a red and a green LED and connect them antiparallel. Then a serie
resistor of let's say 2k2. Connect this combination between GND and the
signal line you want to observe. Keep in mind that this LEDs eat energy. So
if you use them on a line that's meant to power a small circuit, a mouse for
instance, there may not be enough current left to power this circuit.

pieter


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[the Wiz]

bob@shoptalkforums.com (Bob Business) wrote:

Hello,
I have a project that uses a 2 wire connection via RS-232 / DB9 serial
to program it, but nothing is happening, so I thought I could use a
circuit that connects and displays activity via 2 dual color LEDs.
Since I am a programmer by trade, I have no idea how to do this, so I
was wondering if anyone had any plans or ideas. Note that RS does
carry a product like this for $15, but it is DB25, and has lights for
7 data lines. I only need 2.
Thanks,
Bob

The minimum RS232 connection is usually 3 wires transmit, receive, and ground.

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[Jim Large]

the Wiz wrote:

The minimum RS232 connection is usually 3
wires transmit, receive, and ground.

You are assuming that the O.P. wants two-way
communications. I used to have a micrcontroller
board from Circuit Cellar that had "one and a
half" serial ports. One was the console port
(three wires), and the "half" was for a printer.
It only had a Tx signal and ground. There was
no Rx.

-- Jim L.

 

[CFoley1064]

I used to have a micrcontroller
board from Circuit Cellar that had "one and a
half" serial ports. One was the console port
(three wires), and the "half" was for a printer.
It only had a Tx signal and ground. There was
no Rx.

-- Jim L.

Ah, yes. The BCC-52 board, based on the 8052AH-BASIC (no longer made by Intel,
of course). They should've put 41 pins on 'em. Other than that, a lovely,
versatile 8-bit SBC, especially good for beginners. Micromint now has the MCU
made by a 3rd party. The board is especially useful if the customer wants to
be able to understand what the SBC is doing, and may want to tweak it in the
future. As long as you burn in _your_ program on the EPROM (you can do that
from the board, too), they can play to their heart's content, and just cycle
power to go back to the original program they paid for. KISS. They still sell
'em at

http://www.micromint.com

Good luck
Chris