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RS232 issues


Hi people, I am really at odds trying to find an RS232 line driver. My project is a breakout for the RS232 that won't load the connection between two [max 232] points. A port sniffer if you will to log data between the two points.
For all the chips I have searched, they all seem to convert to TTL and that won't work to a 3rd RS232 port.
What I need is RS232 in with RS232 out but a fan out to drive more than one port,,in both directions (TXd and RXd)
Anyone know a chip part number that will meet this.
Trying to avoid wiring 2 MAX232s back to back.
Thanks in advance.


Well-Known Member
Most Helpful Member
What are you trying to connect the monitor output to? Another RS232 device?

The simplest "monitor" connection is an NPN transistor with the emitter grounded, a reasonably high value resistor from the RS232 line to base and a diode between base and emitter to protect against too much negative gate voltage.

Add a pull-up to the emitter and you have a TTL signal for an MCU.
If you need RS232 add a MAX232 or similar driver.

You can use anything up to probably 100K as the base resistor so the load on the RS232 signal will be negligible and have no effect at all.

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