I have read the previous thread on serially addressable LCDs by Steve with great interest. My question on this subject has to do with real-time applications. How good are this kind of LCDs for real-time applications, when in the same bus (I am talking about I2C bus at the 400khz speed) other devices have to be served? For example, in my mp3 player project in the I2C bus I am going to have the DSP (ampifier & mp3 codec), the fm tuner, battery management chips, probably an RTC, etc. To be more specific, the tuning of the fm tuner chip is controlled via the I2C bus and the same stands for the volume for the DSP, but at the same time these information have to be displayed, when they are changed. How good the I2C bus can serve all this functions (display and control functions) without any delays?

The problem is that I am left with only 16 I/O pins (two ports) and with these I have to interface a graphic display (wuth T6963 controller) and some buttons (probabably matrix keyboard) for controlling the player. I was thinking to interface the display via I2C bus with the help of an I2C port expander, but I don't know if it is a good solution for the situation described above. Any suggestions/thoughts? Thanx in advance...

George Pallis