Pic to GSM Phone connection (HSerin problems)

[Rufinus]

OK, i will try again without MAX using inverted mode. How to set it in HSerout command?
I am sure about the RX TX connection, besides, with the pc communication there are no problems.
And i will try also numeric mode (atv0, if i am corect?)

Well, it would be easy to give up on it, but it looks like nobody tried yet with Siemens. And anyways i like doing this things, so i will keep on going untill its working anyhow, and than i will try to get it working with original cable (sometimes i am an optimist )

Thanx for your help, Ioannis, i appreciate it.


P.S. I have a feeling, that this must be some stupid little ditail which is missing. As allways, so..

[Ioannis]

On the matter of Rx Tx connection let me insist on. Try to change and see what happens.

Also with siemens (cannot recall the model) had no problem 2-3 years ago.

Whatever you connect to the PIC as modem and sending "AT" it should reply "OK".

Ioannis

[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.

[Rufinus]

OK, just finished selfmade cable.
Rx and Tx do through the MAX, and CTS(5), RTS(6), DCD(7) are connected to the GND(2) trough 10k resisors. Without this it does not work. Or other way is to connect RTS to CTS straigt, it will communicate with the PC then also. Communication with the PC was fine in both cases. So, sefmade cable is considered to work correctly, at least for the AT commands.

Tried swapping Rx and Tx as Ioannis sugested, but it just made my phone to go off. After restart it was working fine. So, nothing was wrong with my pinout.


Now, NavMicroSystems, i am not that sure about powering cable from COM port. It is rather powered by the phone itself (as strange as it sounds). As a proof i can say, that i was able to communicate with the PC, using original cable with only 3 wires (Rx, Tx, GND), rest of them i disconnected for the experimental sake. And in this configuration it was working with hyperterm or some similar software except original Siemens software, which did not detect the phone. Only when you connect also CTS line, the phone will be detected by the Siemens software.

I should mention again, i'm experimenting on S65 and S55 phones which are rather new, and they are different from older Siemens models, pinout of the phone's interface and connector itself are different.


So, now my setup looks like this: PIC--->MAX232--->MAX232(selfmade cable)--->Pnone

From above, and as NavMicroSystems says, both MAXes can be ommited. Will try then connecting straight PIC to Phone using serout2 in inverted mode.
Wish me good luck

[Rufinus]

Well, i guess, your wishes did work

A little

I did connect it straight with the pic and used inverted mode. And i got the phone dialing! Why didnt it work with pic16f84 then?? Who knows..

So, thanks to all who cared and helped, in particular, NavMicroSystems and Ioannis.


But it still leaves some questions. Why didnt it wont to work with cables??

[Rufinus]

Ooops. It was to early to yell Gloria!
It does work with S55, i am able to send commands to the phone, but not receive from the phone.
And with S65 nothing is working at all. Tried different modes..

[NavMicroSystems]

Rufinus,

I don't have the full specs of S55/S65
but this looks like a problem with the logic levels.
(Presuming your Code is OK)

Could you Scope the phones TX Pin to see wether it is sending anything at all and check it's output level?

You'll probably need a simple Levelshifter (i.e. 2 Transistors)

[Ioannis]

I totally agree with Ralph. If your phone is "listening" what PIC says then PIC should listen too. May be the phone outputs too low voltage levels. So a MAX232 or even a simple circuit with a transistor would help. Test with a scope to see the real levels. What Resistors are you using on Rx - Tx lines?

Ioannis