DS90UB948-Q1: Deserializer holds SCL down and blocks I2C communication

Tomislav Rac

Part Number: DS90UB948-Q1

I'm using serializer 949 connected to host and 948 on the other side. I read register I2C_CONTROL_2 to check FORWARD_CHANNEL_S EQUENCE_ERROR bit and In very rare cases deserializer pulls SCL down and there is no recover from that except reset. BCC_WATCHDOG_CONTROL register has default values and I2C_CONTROL_2 register has the following configuration: I2C_BUS_TIMER_SPEED UP = 1, I2C_BUS_TIMER_DISABLE = 0. I though I2C watchdog will handle this case bit it doesn't. Is there any way to handle this scenario?

over 5 years ago

0 Aaron Heng over 5 years ago

TI__Mastermind 36940 points

Hi Tomislav,

Are you saying the SCL pin pull down once awhile? Or it happened all the time when you try to read the register of I2C_CONTROL_2. Can you check if you get the link established between two devices 949 and 948? It looks like that your master is pulling it down. I will check on my end if I see the same symptom.

Aaron

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

Intellectual 395 points

I have link established between 949 and 948. Everything works fine most of time but it happens (very rare) that when i try to read deserializer register i don't get ACK from 949. Then wait some time (timeout) and try to terminate transfer sending stop bit, but this change nothing because SCL is pulled down, and then only reset is solution. Maybe we have some problems in hardware, but I wonder would I2C watchdog on deserilaizer handle situation when it holds SCL line to long (stretching)?

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

TI__Mastermind 36940 points

Hi Tomislav,

Could you please capture the scope photo on the bus?

Aaron

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

TI__Mastermind 36940 points

Hi Tomislav,

Just checking back with you if you have a chance to capture the I2C transaction.

Aaron

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

TI__Mastermind 36940 points

Hi Tomislav,

Since you don't respond, I assume that you resolve the issue.

Aaron

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

Intellectual 395 points

Hi Aron,

Yes, issue is resolved. You can close the issue.

Thanks for support!

Best regards,

Tomislav

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

TI__Mastermind 36940 points

Hi Tomislav,

I am glad that you were able to resolve the issue. Could you please explain what you have done in order to get it working? Thank you.

Aaron

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DS90UB948-Q1: Deserializer holds SCL down and blocks I2C communication