Arduino Diecimila and RS-232 serial communication

I'm getting back to my Arduino Diecimila (ATmega168) after many years of it sitting on the shelf.

I want to control a piece of bench test equipment that has RS-232 control feature. I want to monitor an external temperature (thermocouple? thermistor?) and control the test equipment based on this input.

I have the interface manual for the equipment so all that it requires is at hand.

Should I consider using the Diecimila for this? I see a serial shield is available from Sparkfun to make the serial communications simpler:

Serial shield

Or is there a better Arduino (or other platform?) that will make this straightforward?

Thanks!

Do you need actual RS-232 level signals -- ie: +/- 12V signalling? Or is 5V logic level serial going to be okay? If you need RS-232, then an RS-232 line driver like a MAX232 is going to be needed.

Do you need to simultaneously talk to the Arduino via USB while it talks to your instrument? How fast is the serial data rate for your instrument? Is full-duplex communication with it required?

Depending on the answers to these things you may or may not be able to use the single hardware UART on the ATMega168 for your instrument and you may or may not be able to use a software serial implementation to talk to it as well.

gardner: Do you need actual RS-232 level signals -- ie: +/- 12V signalling? Or is 5V logic level serial going to be okay? If you need RS-232, then an RS-232 line driver like a MAX232 is going to be needed.

I emailed with someone who has done something like this with Arduino and similar equipment. Says that TTL is OK, but incoming (receive) line from equipment will be 12-15v. Does this need to be conditioned before connected to ATmega?

Do you need to simultaneously talk to the Arduino via USB while it talks to your instrument? How fast is the serial data rate for your instrument? Is full-duplex communication with it required?

No USB communication is needed at all. Arduino simply checks sensors and adjusts this equipment via RS232.

Depending on the answers to these things you may or may not be able to use the single hardware UART on the ATMega168 for your instrument and you may or may not be able to use a software serial implementation to talk to it as well.

The remaining question is: is handshaking needed? If so, how using only ATmega? or how with driver (MAX232 etc.)? Is it set or clear DTS DTR, etc. and read or write byte? Samples or links to examples?

Thanks.

A follow-up question:

What does the MAX232 do that a level-shifter doesn't do? ::

Sparkfun level shifter

Thanks.

A MAX232 has an integrated charge pump to generate the +/-12V to do the RS232 signalling and has a pair of bus transmitters and receivers. http://www.maximintegrated.com/en/products/interface/transceivers/MAX232.html It's the same general idea, but more sophisticated than the sparkfun one you mentioned. If the instrument you want to talk to is known to be TTL tolerant, the sparkfun job should be fine.

If you don't have to talk to the USB and your instrument at the same time, then you can use the hardware UART, which will make things a bit more flexible and reliable. You will still likely have to use a software serial to do initial testing and debugging.