Can i user newsoftserial to connect to a rs232 dev

Hello i want to connect to a rs232 device. . the modem that in fact is siemens s35 with rs232 cable has its own power so I'm planning to make the connection from the db9 serial port using only tx,rx, and ground to connect to arduino... Can this be made or do i have to buy something like this ? http://www.cutedigi.com/product_info.php?products_id=4329

how about a garmin gps device that outputs rs232 ? what i want to understand is that using newsoft serial i can connect the same serial devices i connect to the pc , not requiring power of course..

Thanks btw i want to connect the gsm phone to send some sms's.

Regards.

You need to do some research on RS232 input/output vs. TTL input/output. Notice that RS232 output is +12V/-12V and inverted compared to TTL's 0/+5V.

Do you really want to feed +12V into an input pin on YOUR Arduino? Do you really want to feed -12V into an input pin?

You can use NewSoftSerial (note that it is all one word) to do nearly anything that a hardware serial port can do.

Can you use NEWsoftserial?

Yes! You should! (Better than SoftwareSerial, no downside, as far as I’m aware… if someone disagrees… maybe start a separate thread for that?)

And, hoping everyone will forgive a cross-post…

RS-232 // Arduino Rx Tx…

You shouldn’t try to get away with connecting an “RS232” signal direct to an Arduino… or the signal might not actually be RS232, or it might be an enhanced RS232 that doesn’t care/ can drive 5v (or 3.3v) lines…

*** BUT *** there are REAL, potentially equipment wrecking issues here!!!

See the “Hardware” section, a little way down in…

http://www.arunet.co.uk/tkboyd/ele1sp.htm

That will also steer you towards a good little RS232/Arduino(etc) interface…

Wulfden PA4B $11

sorry for my ignorance, i can check if the phone or even the garmin give 12v ?
i don’t believe it because they are powered by so lower voltage batteries…
its possible to have the device talking ttl serial and that would work with a normal pc serial port ? no ?
better to buy the serial shield…