DS90UB948-Q1: I2C no Ack/Nack problem

Charlotte Allhammar

Part Number: DS90UB948-Q1
Other Parts Discussed in Thread: DS90UB941AS-Q1

We have some problems with disturbances on the coax link between the desrializer and a serializer (DS90UB941AS-Q1). The link is stable enough to have lock set and also to reflect registers like remote ID.

When sending I2C messages to the serializer using the remote ID loaded we sometimes succeed but sometimes we never get an ACK. In these times the clock line is set low forever. I though keeping the register I2C_BUS_TIMER_DISABLE set to 0 would make the deserializer see this issue and unlock the line but that never seem to happen.

Any ideas how to detect this, solve it and why the register seems not to work at all?

Charlotte

over 6 years ago

0 Sally Cheung95 over 6 years ago

TI__Expert 5480 points

Hi Charlotte,

Do you have I2C pass through enabled? Please try checking both devices.

0 Charlotte Allhammar over 6 years ago in reply to Sally Cheung95

Prodigy 40 points

Of course! As I mentioned it's not always it fails. We have disturbances on the coax line which are worked with in parallel but we do want a robust system who will not crash completely at one fail.

We're running master I2C on the Deserializer side and using interrupts to detect ack/nack bits. We could of course try to add a manual timeout in our own code but reading the register description I would assume that it's there just for theese lockings. I'm I wrong?

I have an oscillator connected to the I2C line on the deserializer side but can never see this: "If SDA is low and no signaling occurs, the device will attempt to clear the bus by driving 9 clocks on SCL" - taken from the data sheet.

0 Charlotte Allhammar over 6 years ago in reply to Charlotte Allhammar

Prodigy 40 points

Also if pass through is disabled I will simply get a nack back.

I'm also monitoring the "LOCK" flag on the deserializer side and do not try to send anything unless it's set.

0 Vijaya Ceekala over 6 years ago in reply to Charlotte Allhammar

TI__Intellectual 2930 points

Hello

You can also use the BCC watchdog timer to terminate a transaction cleanly if you dont see a response within certain time This would be Register0x4

Thanks

Vijay

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DS90UB948-Q1: I2C no Ack/Nack problem