I hope this is the right forum in the board to post this query.
I would be designing an interactive voice response (IVR) system using the SIM GSM modem.
The system will pick up the phone at the third ring and give a voice message out :
press 1 for this, press 2 for that , etc etc.
When the person presses the appropriate number some action will be taken by the micro board.
The system also should support making voice calls from this equipment when the above situation is not happening.
I need help on two aspects :
1) How to trap the button pressed by the remote user ?Is there any IC which can do this ?
2) How to have a parallel system for both voice conversation and IVR which can be switched as required ?
Does anyone have a reference design which they can point me to.
Thanks for that Nandhu.
Yes I am aware of CM8870 to decode the DTMF tones.
The issue is, the GSM modem which I have, has only an UART and a connector for a conventional handset.
Would I be able to pick up the DTMF from the hand set connection and feed it to CM8870 ?
Thanks Nandhu and Manish for confirming that the concept is feasible.
Umery I am looking at the datasheet. Thanks for the tip.
I will revert with any queries/results.
Thanks for your interest. The project which you pointed me to uses land line. Actually I am doing it with a GSM modem at one end.
Hence the main issue was if the DTMF tones would be sent out by the modem over its handset connection.
Going by the posts from our colleagues its seems it is so, I would be making a circuit and testing it out soon.
Hi,
You can generate DTMF signal either by IC or by making your own circuit, but I advise you to go for the IC.
You can also use the TCM5589N tone generator IC and simply connect the speaker output with the handset and use the control lines to generate the required DTMF signal to be sent out.It doesn't matter whether you are using the landline or GSM modem, you just needs to have the two analog voice carring wires, just connect it's output in parallel to this one and all is done.GSM modem has nothing to do with it, if you want your GSM SIM modem to pick the phone call on the 3rd ring, program it with
Code:
ATS0 = 3 -> this will force it to pick the call on 3rd ring
AT+CHFA=1 -> set this command for the ear piece configuration
just double check the syntax of commands, to ensure error free operation.
You can use the ISD2560,75,90,120 series ICs for voice generations.
There was an IC with CM8890, if I remember it correctly, but I can't find it's datasheet on internet, so that's why I'm not sure at this time of writing about the IC existence.CM8890 was a both decoder/generator for DTMF.