DS90UB927Q-Q1: The DS90UB927's IIC clock is pulled down

user5006961

Part Number: DS90UB927Q-Q1

HI TI employees,

My client USES ds90ub927/928 design, and has encountered some problems at present，they found that DS90UB927's I2C clock signal was abnormal，this is shown below.

May I ask what caused it and how to solve it.

over 6 years ago

0 Casey McCrea over 6 years ago

TI__Guru** 103215 points

Hello,

Sorry for the delay but it is a US holiday today and most team members will also be out on Friday so please expect a response early next week.

Best Regards,

Casey

0 Charley Cai over 6 years ago

TI__Genius 12866 points

Can i get a little more info on the system?

What is the pull up voltage and what is the pull up resistor value?

Does this happen at random location or follows a pattern?

Is the waveform measured at the 927 input side?

Best Regards,

Charley Cai

0 user5006961 over 6 years ago in reply to Charley Cai

Intellectual 805 points

Hello

The customer designed a touch screen that USES a 927/928 that displays images but does not respond to touch.

Tests found that when the 928 returned the signal, the I2C clock signal was pulled down，The clock comes from the ARM next to the 927 chip, and the I2C is standard hardware I2C.

It is pulled down exactly when it is 928 ACK, the ninth digit of the clock，when the clock is pulled down, the data can't be transferred, and the screen on the 928 is not touched

0 Charley Cai over 6 years ago in reply to user5006961

TI__Genius 12866 points

Could you check if the I2C master supports clock stretching?

What is the pull up resistor value?

Best Regards,

Charley Cai

0 Casey McCrea over 6 years ago in reply to Charley Cai

TI__Guru** 103215 points

Hello,

Any feedback here? Is the issue resolved?

Thanks,

Casey

0 user5006961 over 6 years ago in reply to Casey McCrea

Intellectual 805 points

This problem has been solved. It is found that the problem is not TI, but MTK does not allow external devices to lower his clock

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DS90UB927Q-Q1: The DS90UB927's IIC clock is pulled down