Using Arduino as RS232 bridge

Projects Networking, Protocols, and Devices
1

Hi,

I need to read data from a device that (I think) uses RS232 standard. I need to know if I can connect the TX cable from this device to Pin1 in the arduino and read the device data through USB in the PC.

Device cable -> Pin1 -> read data through USB It works?

Thanks a lot.

2

No. RS-232 signalling uses +12V and -12V whereas Arduino uses +5V and ground. If you hook the RS-232 Tx to the Arduino pin it'll probably blow something up.

Pete

3

Ok, sorry. My fault. It's not RS232, it's a 5V serial signal. O:-)

What I want to know is if on the PC side I will receive the information written at Pin1.

Thanks a lot.

4

bicho_visacoso:
Ok, sorry. My fault. It's not RS232, it's a 5V serial signal. O:-)

What I want to know is if on the PC side I will receive the information written at Pin1.

Thanks a lot.

No, as normally pin 1 will be set high by the 328p chip and if you wire a TTL signal to pin 1 and when it tries to go to a low state there will be a direct short cicuit condition between the arduino 328p chip and whatever is driving the external serial signal.

There is one way to utilize the arduino serial usb link with an external TTL serial device and that is to wire a jumper between a ground pin and the reset pin. That will hold the arduino 328p chip in reset condition which turns off all I/O pins (tri-state) and then you are free to use pins 0 and 1 to commuicate with a PC through the arduino's usb serial convert chip (8u2 chip on new boards, FTDI chip on older boards). What this is doing is effectivly disabling the arduino's processor chip and you would just be utilizing the usb serial link components. You can accomplish the same thing by just removing the 328p chip from it's socket.

Don't forget you have to wire a common ground wire between the arduino board and a ground connection on whatever is driving the serial signals.

Lefty

5

Thanks a lot. That's very useful. :slight_smile:

Regards.