Connect to ohter RS 232 via serial Tx and Rx

Projects Networking, Protocols, and Devices
1

Hi

I'm a complete noob when it comes to hardware (Bought my first Arduino 2560 last week). I did a search and could not find a related thread to my question. If there is one I apologize. I just want to make absolutely sure so that i don't burn a port on my Ardruino or even the other device.

I just need to know, how would i go about connecting one of the four serial ports to another RS232 device. How would i need to build the plug, wire the connections on the RS 232 plug up with the Ardruino. I'm not concerned about the Ardruino getting power from the RS 232, i only need data transfers. Do i only need to connect the Tx to pin 2 and Rx to pin 3 of the RS 232 plug and thats it?

Thank you

2

Do i only need to connect the Tx to pin 2 and Rx to pin 3 of the RS 232 plug and thats it?

No, and it's a good thing you asked because that could well blow up the Arduino input.

RS-232 has voltage levels of +-12v, you have to connect through some level conversion, typically this is done with a chip like the MAX232.

Also RS-232 inverts the data, but the MAX232 will re-invert it so you get the correct polarity.

Rob

3

Hi there,

Yup. Graynomad is quite correct.

When you say 4 serial ports(which is true) to other RS232 device (do you mean serial or actually serial via RS232?), are you connecting directly to say another computers serial RS232 port? Because they run at 12v and could damage your Mega.

If you want to connect ports 0, 1, 2, or 3 directly to RS232, you need to have an RS232 transceiver in front of each port.
This takes a Rs232 signal in and reduces it down to 5v so the Mega can handle it. The Megas Tx out goes to the RS232 IC and is bumped up via 12v charge pumps to proper RS232 voltage and then sent out. This is the reason for Mega having serial 0 setup as USB as it gets you working with serial from your computer via USB at 5v.

If it is simply serial communication between Mega and other MCU's like XBee radios, no problem. Simply connect Tx to others Rx and Rx to others Tx.

I hope this helps.

ciao

4

Will this device also do the job?
http://www.netram.co.za/Electronics/Interfacing/RS232-Shifter-SMD.html

Thank you for the replies! Saved me a serial port! :sweat_smile:

5

Yup.

That little monster should work nicely.

Do you happen know the US dollar equivalent of the R140 cost for the part?

6

if R140 is indian Rupiah just use googles built in currency convertor

GOOGLE : 140 INR IN USD (INR = INdian Rupiah)

but co.za is not India I guess maybe South African Rand?

GOOGLE : 140 ZAR IN USD (ZAR = Zuid Afrikaans Rand)

7

Yes, that would be

140 South African rands = 20.35 U.S. dollars

Thank you!