GSM modem not working with PIC! Both modem & PIC work fine with PC

[financecatalyst]

Thanks for the answer. The problem is that I am using a complete modem. I am sure it has MAX232 inbuilt. I just have to connect the rs232 serial cable to it and my pc. I cannot take out MAX232 from the modem.
It's pin 2 (DB9-connector) has a voltage of -5.85V.

Is it possible that I have to put more pins ground apart from pin5 of DB9-Connector? Thanks

[Ioannis]

Although I am sure it works on PC with just TX, RX nd Gnd, have tried to connect to PC just with these 3 wires?

Also are you sure about 4800 baud?

Ioannis

[financecatalyst]

Although I am sure it works on PC with just TX, RX nd Gnd, have tried to connect to PC just with these 3 wires?

I tried it now, I could not type in my hyperterminal anymore as soon as I connected my modem to the PC with only 3 wires. As soon as I connected 9 pin serial cable, everything starts working fine.

Also are you sure about 4800 baud?

Yes, baud rate is 4800.

[aratti]

I tried it now, I could not type in my hyperterminal anymore as soon as I connected my modem to the PC with only 3 wires. As soon as I connected 9 pin serial cable, everything starts working fine.

Was hyperterminal in hand shaking mode?

See the modem manual, if the modem is in handshaking mode by default, in such a case you have to set it for no flux controll.

Al.

[financecatalyst]

Was hyperterminal in hand shaking mode?

See the modem manual, if the modem is in handshaking mode by default, in such a case you have to set it for no flux controll.

Al.

I have not got the manual but I have opened the modem and saw that sim300 is the module which the modem is built on. I have checked sim300 datasheet but could not understand many things as I do not have too much of a technical background.

Can you advise me, what AT commands can do this job.
I also find this on the net - http://www.london-electronics.com/alpha_232_conns.gif
Is this an alternate way to go to solve this problem (RTC - CTS connected together & also pins 6,1,4 connected together? I do not want to try it unless it is safe to do so, only have 1 modem

Also, how can I find out if Hyperterminal is in Handshaking mode? One more thing I would like to mention here which I read from sim300 datasheet is that the modem supports and by default has Autobaud from 1200 to 19200.

[aratti]

Also, how can I find out if Hyperterminal is in Handshaking mode?

When you set the baud rate you can set also the flow mode. See the three snaps attached.

Al.

[financecatalyst]

When you set the baud rate you can set also the flow mode. See the three snaps attached.

Al.

No, the handshake mode is "None".