DS90UB925Q-Q1: can't change 0xC6 register

jason larson1

Part Number: DS90UB925Q-Q1

I have a set up that has a DS90UB925 (device 1) connected to a DS90UB926(device 2) and then goes thorough some isolation that back to a DS90UB925(device 3) and then to a DS90UB926(device 4) then I get the data out. I have a master I2C connected to the last 926 (device 4) and over I2C I can read and write almost all registers in the first 925 (device 1). For some reason I can't write to the 0xC6 register in 925 (device 1). I Also tried writing to 0xC6 in the 925(device 3) and no luck either. What would stop me from setting this register? I did check the 0x05 bit 2 reg in the 925 and it is 0.

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Jason,

This particular register may be locked to local writes only. We will need to check that - please give a few days for us to look into it.

Best Regards,

Casey

0 Bryan Kahler over 5 years ago in reply to Casey McCrea

TI__Mastermind 25955 points

Hi Jason,

Thank you for your patience. I will have an update for you by Friday 11/22.

Sincerely,
Bryan Kahler

0 jason larson1 over 5 years ago in reply to Bryan Kahler

Prodigy 190 points

Thanks for the update. I did verify if I jumper from the micro to the DS90UB95 directly I can change the register. But since we are operating in camera mode we can't have it connected that way. I look forward to your finding on Friday.

0 Bryan Kahler over 5 years ago in reply to jason larson1

TI__Mastermind 25955 points

Hi Jason,

I have been able to reproduce the issue in the lab and can confirm that the 925 only allows access to 0xC6 via local I2C. It cannot be modified across the backchannel via the 926.

Thank you for the feedback - this issue has been noted for the next datasheet update.

Sincerely,
Bryan Kahler

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DS90UB925Q-Q1: can't change 0xC6 register