Pic to GSM Phone connection (HSerin problems)

[NavMicroSystems]

Rufinus,

I guess the problem is with the Siemens Datacable.
Most cables have some embedded electronics.
(At least a level shifter, probably more..)

This is usually powered from the PCs serial port (DTR & RTS)
So if you are using one of these cables to connect the phone you will need a MAX232 on the PIC end as well.
And you have to set the correct levels at DTR & RTS on the MAX232 at the PIC end in order to supply the cables embedded electronics.

As far as I can remember The Siemens interface is 5V tolerant, so all you need is 3 straight wires from the PIC to the Phone (no MAX232 at all).
But then you'll have to use SERIN2 /SEROUT2 instead of HSERIN/HSEROUT since HSERIN/HSEROUT doesn't allow to toggle between true/inverted mode.