Caller Line Identification with Microcontrollers

Hi,

I am thinking of developing a caller line identification system using a PIC micro-controller. I assume the CLI mechanism is based on DTMF here and not FSK. (Since I see nothing with a modem attached to the line. I tried AT commands but I just see "RING")

So my design consists of 3 segments.

1. MT8870 to decode DTMF.
2. 16F877A to process the output from MT8870
3. SSD Driver unit.

Initially I am planning to test the unit with 16 x 2 LCD but my plan is to expand the circuit to drive 10 CC SSDs. (Yes, I need a good visibility than a small LCD)

So my questions are,

1. Where can I find the protocol used with DTMF caller line identification. I will need that while implementing the PIC code algorithm.

2. How should I drive 10 SSDs. (Multiplexing??)

Thanks,

Chathusrilanka

HI

Most caller ID best on FSK and not DTMF signaling

Use a dedicated IC to decode Caller ID from phone line

The new family f microcontroller best on the COTEX M3 or M0 cand decode the FSK without the need for special IC only line interface

All the best

Bobi

The microcontroller specialist

There isn't time between ringing bursts to send CLI data by DTMF, typically it would take 40mS per digit and it wouldn't directly allow anything but numbers.

Most if not all CLI systems use FSK, I think 1200 bauds is standard with data sent 'backwards', last character first and with certain bytes reserved for control purposes. The biggest difference between telco's is when the data is sent, some put a 'wake-up' tone on the line, followed by the CLI data then the first ring burst, some sent it between the ring bursts.

Brian.

Hi,

I wonder if you guys can point out some specific (and available) Chips to deal with DTMF and caller id detection. It will be great if you can point me to some sample circuits as well.

Cheers!