I'm sorry for annoying you, but I've some problems with the communication between atmega8 and AD5933 (specifically the chip is the one on the EVALAD5933EBZ, with SCL and SDA leads cut and powered through VDD-EXT).
I wrote the code for I2C communication, but it doesn't work!!!! They never talk! The microcontroller sends the start condition but never receive/recognize the acknowledge. I saw the signals with the scope and both, the frequency and the level voltage, are correct, even if there are (only on the SDA) some spikes on the transition that I don't understand...
Both are powered at 5V, so I don't need to add a level shifter in addition to the pull up resistors.
I hope someone can help me to solve it!
I attached the code (written in assembler): as it doesn't work at all, I uploaded a "reduced" version that only send the start condition and if it get it send the stop condition. The 3 pins of portD are used to turn on/off the leds, that helps me to understand quickly what happens.