Sometimes, MCU (SCL, SDA) can't receive an ACK signal (acknowlege bit) from TPS23851 (SCL, SDAin, SDAout) after MCU have sent I2C write command to TPS23851. So, MCU need rewrite it again and again.
The problem is always occurred in 1st byte. The probility is more than 1/10 and rewrite times sometimes may be more than 10 times.
I guess that the possible resaons may come from TPS23851 not receiving correct data from MCU or receiving incorrect device address.
But I compare the waveform and timing from MCU GPIO pins (software simulating I2C bus protocol ) for both OK and NG cases by LA and scope. They seems all same (I have kept these snapshot from LA). The I2C clock period is around 360us. And our hardware between I2C master (MCU) and I2C slave (TPS32851) is isolated by phto coupler.
Thanks.
Regards,
Derli