RS232 communications question

[runtime]

Hello all,

I have a PIC18F252 attached to a Wavecom modem, the Wavecom modem has the following I/O Electrical Characteristics:

Digital Inputs:
DTR,TXD,RTS,RESET: Input High = Min 3,675V, Input Low = Max 1.4V

Digital Outputs:
DCD,CTS,DSR,RI,RXD: Output High = Min 4V, Output Low = Max 0.4V
Current Drive: 2ma

I have wired only the TX, RX and GND pins, the question is: can I wire directly the PIC pins to the Wavecom pins or do I need a resistor or something to protect the PIC?

Thank you in advance
Peter

[PCM programmer]

Provided that the PIC is running at +5v, it should work OK.
(at least in terms of the voltage levels).

Details:
The 18F452 has either CMOS or TTL input pins. You can see
this by looking in the data sheet in this section:
TABLE 1-2: PIC18F2X2 PINOUT I/O DESCRIPTIONS

Then find out the actual voltage levels used by each type
of input pin, in this section:
22.2 DC Characteristics: PIC18FXX2 (Industrial, Extended)
Compare the i/o voltages on your Modem to those listed
in the data sheet, and you'll see that it should work.

[bdavis]

Runtime -

I have seen several posts concerning GSM modems, and the WaveCom seems popular. I looked at their website, and they don't seem to give out much specific information (ie: data sheets, pricing, etc). I realize most posts are related to big company projects, but my interest was just educational and for home use (home automation). I was wonderin how much those puppies cost, and if there are big licensing restrictions on them - ie: can someone buy just one? Are they cheap? (ie: cell phones are fairly cheap, but I suspect the modems are much more...).

Thanks!

[runtime]

bdavis,

Sorry I didn't answer earlier. The Wavecom modems are great, they only manufacture the GSM module, please take a look at www.Multitech.com part # MTSMC-G-F2, that's the one I'm using, its a SocketModem with a Wavecom module. The price: about $100.00

HTH
RunTime