DS90UB928Q-Q1: Can we change the line speed of the I2C?

Danilo A.

Hi Team,

A customer wants to confirm if the line speed of the I2C can be changed. Please refer to the screenshot below.

CH1 & CH2 are input to DS90UB927QSQ and CH3 & CH4 are output from DS90UB928Q-Q1 to a slave device. The Line Rate was changed from 100kHx to 50kHz, but the I2C line rate from the DS90UB928Q-Q1 to Slave remained at 65kHz

He cannot identify any registers in the devices that allow him to do this and he would like to understand why the line rate appears to be fixed at 65kHz from the DS90UB928Q-Q1 to the Slave. Also changing the input frequency to DS90UB927QSQ PCLK also has no effect. Is it fixed from the 10Mbps back channel rate?

Regards,

Danilo

over 5 years ago

0 Aaron Heng over 5 years ago

TI__Mastermind 40270 points

Hi Danilo,

The device is only supported 100kHz or 400kHz, but 50kHz.

Aaron

0 Lee Anthony over 5 years ago in reply to Aaron Heng

Prodigy 190 points

Thanks for the clarifiction.

Can anyone explain why the Des run at 65kHz when the Ser is running at 100 kHz (Please reference to the images) ?

0 Aaron Heng over 5 years ago in reply to Lee Anthony

TI__Mastermind 40270 points

Hi Anthony,

Please see section 5 in the apps note.

Aaron

0 Aaron Heng over 5 years ago in reply to Aaron Heng

TI__Mastermind 40270 points

Hi Anthony,

I was too quick and forgot to mention about the registers. There are two registers that you can adjust the SCL High Time and SCL Low Time 0x26 and 0x27 respectively. The default value for the frequency is 75.7kHz. Your scope photo showed 65.5kHz with 20% variance. You can increase or decrease the frequency using these registers.

Hope this helps. Let me know if you have further questions.

Aaron

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DS90UB928Q-Q1: Can we change the line speed of the I2C?