MMA8653FC I2C communication issue

[Lurkersoo]

Hello, our customer try to communicate the MMA8653FC via I2C, and they try to read the chip ID(register address: 0x0D), it can'r send back the right value. We testt the SDA and SCL waveform. We found the ACK signal is abnormal. Enclosed the SDA AND SCL waveform. Do you know what's wrong with it?

Thanks!

Best Regards,

Shaowei Su

[TomasVaverka]

Hi Shaowei,

A common problem with the read operation is sending a stop condition (a low to high transition of SDA while SCL is high) after the second byte (in this case 0x0D). The correct way is to release the SDA line (so that it transitiones to high) before the SCL line goes high. It is not clear from your pictures, please double check it on an oscilloscope.

A single byte read from the WHO_AM_I register 0x0D looks like this (note it is for the MMA8652FC whose ID is 0x4A):

I hope it helps.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct". Thank you.