TC35i GSM With PIC 16F690 help

[financecatalyst]

Hi
Can someone help me please providing a schematic to link up my PIC with TC35i GSM modem.

I have seen an schematic provided by Aratti, linking TC35i with 16F873.

What I would like to ask is why MAX232 is used? What does this IC actually do and why not to connect the PIC directly to the TC35i?

Damien

[pedja089]

max 232 is logic level converter. It converts RS232 logic level to ttl logic level and ttl to RS232. You should look datasheet.

[financecatalyst]

Thanks for the info but since I am fairly new to this field, can you guide me as to where I can read about TTL & RS-232 type signals and difference between them.

[mackrackit]

http://en.wikipedia.org/wiki/RS-232

http://en.wikipedia.org/wiki/Transis...ansistor_logic

Is a start...

[pedja089]

On google or wiki
RS232 standard:
logic "1" is -3 to -15V
logic "0" is 3 to 15v
-3 to 3 is not defined
TTL standard:
logic "1" is 2 to Vcc (usually Vcc=5V)
logic "0" is 0 to 0.8V
Edit:
0.8 to 2V isn't defied

[financecatalyst]

On google or wiki
RS232 standard:
logic "1" is -3 to -15V
logic "0" is 3 to 15v
-3 to 3 is not defined
TTL standard:
logic "1" is 2 to Vcc (usually Vcc=5V)
logic "0" is 0 to 0.8V
Edit:
0.8 to 2V isn't defied

Thanks. I am trying to send an SMS using TC35i & 16F690. I tried to replicate the schematic at this link: http://techni.caliti.es/blog/2008/12...ontroller.html
I used the pins 10 & 12 of 16f690 instead of 17 & 18 of 16F873. Hope it will work

[aratti]

I used the pins 10 & 12 of 16f690 instead of 17 & 18 of 16F873. Hope it will work

If you have in mind to use the downloaded software, the answer is IT WILL NOT WORK.

If you will write your own software the answer is YES IT WILL WORK.

Al.