Connecting directly using RS-232?

Do you have some schematics for it?

It is in the data sheet of what ever converter chip you decide to use.

Grumpy_Mike:
Yes you need to use an RS232 to TTL level converter chip. I use the MAX202 but there are lots of them. You then connect the chip to pins 0 & 1.

You will lose the automatic reset feature used to upload sketches from the Arduino IDE unless you also convert the RS-232 DTR signal to a ttl level and then through a series wired .1ufd cap to the arduino reset pin. Unless you are willing to just use the manual reset switch when uploading sketches, but you will have to learn the timing of the reset switch.

Lefty

For an example of using this chip along with the auto reset see the schematic in this project
http://www.thebox.myzen.co.uk/Hardware/CNC_Conversion.html

I have now ordered som MAX202's... I don't need the auto-reset functionality, as the chip isn't going to be reprogrammed. What I do need however, is a simple wiring diagram to connect it. I'm quite sure I understand the diiagram from the CNC-thingy (which was ultra cool, by the way) - but could somone draw it up, with just the basic send/recive-functionality?

Will this do? Or, do I need something connected to pin 6 and 15 (on the MAX202), despite not using the reset?

You are not, of course, required to use pins 0 and 1 (the hardware serial port). You can use NewSoftSerial and any two other pins.

Unless you have a Mega, with 4 hardware serial ports...

You may also find the following useful...

But, other than the fact that I could use other digital ports, would the above work? Would II be able to send and receive commands from my arduino?

Yes but you have included the reset on pin 9

So, I can leave out the connection between pin 9 (on the Max202) and pin 1 ?

Yes if you don't want the auto reset.

But, other than the fact that I could use other digital ports

Which "above"? (Rhetorical). The page I gave tells you how to send and receive commands. You have to be able to program the connected device, unless it is already set up to hold up its end of the "conversation", though.

The arduino is allready programmed, and the configuration is final.

(Arduino) configuration final...

Ah! That simiplifies answering considerably, as your choices are considerably reduced.

Do you need to go through a USB link? No... as I think has already been established.

So how to connect the pins on the Arduino to the "outside world"?

Yes, the circuit given will do it. But why re-invent the wheel? There are several people selling, at no great premium, boards with the electronics you need.

Sorry to keep banging on about it, but...

.. also has that information.

Will this do? Or, do I need something connected to pin 6 and 15 (on the MAX202), despite not using the reset?

I, finally, got around to making the circuit - but the MAX202 seems to send out a constant stream of garbage... What have I forgotten?

What have I forgotten?

The baud rate?
Must be the same in TX and RX.

And how do I set that?

The serial begin sets it at the arduino end.
You haven't said what the other end is but there will be some sort of port configuration box,
you need to set this to 9600 baud, 8 data bits, one stop bit, one start bit, and no parity