Hi all,

Thank you all for your precious advice on the problem of decoding DTMF from MT8880.

I have resolved it and the solution was just under the nose that I couldn't see.

The problem was:

After initializing MT8880 the last data out on the nibble is #0000B which clears the ports.

Just after this instruction it cannot read the data, as is like intel port structure.

Solution:

Before reading any data in the nibble ports have to be set to high and that's all.



What a lesson for a novice for me, the harder way.

Simon