Hi,
I have an intercom in the building based on 2-wire RF-232 serial communication. I would like to listen / sniff on the data sent / received between my headset and the entrance. I've come across a few tutorials that listen, spy, sniff on the communication between two devices with an Arduino. But I still haven't understood exactly how it works, and how to replicate it, and the potential risks involved.
I understand that RF-232 might work on -/+ 12V and I'm not sure the Arduino Uno or the Arduino Nano are capable of handling it. However from what I understand the Arduino is convert TTF to Serial for the onboard USB port, so this will handle the -/+ 12V, so should be an issue?
Intercom (entrance) Wire split (1-to-2) Arduino Intercom (headset)
TX ----------------------------------|--------------------------------> RX
|--------------------------------------------------------> RX
RX would be the same principle just the other way around.
Is this correct?
If you put ±12 volt to the Arduino it WILL be damaged. There are chips like the MAX 232, 233 that will shift the ±12 volt signals to 5 volt TTL .Do a search for RS232 to TTL converter.
groundfungus:
If you put ±12 volt to the Arduino it WILL be damaged. There are chips like the MAX 232, 233 that will shift the ±12 volt signals to 5 volt TTL .Do a search for RS232 to TTL converter.
However my understanding is that the converter chip in the Arduino converting RS-232 to TTL will handle the -/+12 V (based on this tutorial by Jeremy Blum @ 3:10 - 3:30 in the tutorial (link) - Have I misunderstood it?
It may be that older Arduino boards had a converter for ±12volt RS232 to TTL but the newer boards have USB to TTL converters. You will need the converter if you have a board that connects with USB. You might want to think about using a software serial port for your sniffer (with a converter). That way you can reserve the hardware serial port (USB) for program upload and debugging.
Ok,
I just bought 10 of these MAX3232 chip boards (link), anything else that I would need?
anything else that I would need?
That, I am unsure about. The point of my post was that directly connecting The higher voltage RS232 would damage your Arduino and the solution to that problem is the converter. You may need diodes between your tap and the existing line to isolate the tap. Hopefully, a member with that knowledge will hep.