Hello,
Anybody have using an HT9200A (serial DTMF dialer)?
If yes, how do I must interface it with the phone line using an isolation transformer (1:1)?
I am trying to build a DTMF dialer using an ATmega8 to control this HT9200A, but I am not sure regarding how I do to interface it.
Your help will be appreciated.
Thank you in advance.
Generating the dtmf tones with the avr is also possible.... search here for c code
Google DAA or DAA circuit.
JC
The OP's issue is not tone generation, it is the line interface. Surely, the data sheet for that dialer must describe a line interface?
[Edit]
The application note is here.
http://www.holtek.com.tw/english/tech/appnote/comm/pdf/ha0037e.pdf
and the data sheet is here
[url]
http://www.holtek.com.tw/pdf/com...
[/url]
App note and data sheet tell how to use the SPI serial interface.
It will NOT interface directly to the phone line through a 1:1 transformer because it expects a 5K load, not 600 ohm load. You will need some sort of line interface circuit. But, you will also need this if you use any of the other DTM generation schemes suggested.
[/edit]
Jim
I have used in the past a pSoc with internal dtmf dialer to do this, but the problem was that the dtmf output wasn't compatible with the TBR21 standard.
I believe that there will be the same problem using any uC to do this.
The HT9200A is a simple SPI controlled dtmf ic, and if you read the datasheet it's very easy to use.
Michael
