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High error rate in I2C Communication between Concerto and Atmega32

Hi all,

I'm developing an I2C comm between a TI MCU (Concerto F28M35) and Atmel AVR (Atmega32). The tranmission and reception is buggy and plagued with transmission error although there are several data bytes got through, oscilloscope waveforms of SCL & SDA pulses are jiggling and unstable. I use the internal pull-up of the Concerto (Vcc = 3.3V) instead of external pullup.

I wonder if I should pull SDA and SCL to 5V as the AVR maximum operating voltage is only 4.5V, and I'm not sure the Concerto could handle 5V pull-up. In case I cannot pull SDA & SCL to 5V, can I pull them up to 3.3V and still can get the I2C working correctly?