ADC121C021: ADC121C021 I2C Write Intermittently Doesn't Update Registers

Stephen Goodman

Part Number: ADC121C021

I've found that writing to the I2C registers sometimes doesn't actually update the register. Once it happens I am unable to write to any register but can perform reads successfully. I can make it come out of this state by performing a conversion (reading register 0), then I can write to the registers again.

I haven't found any cause for this. I2C seems fine, there is another device on the bus that works without issue. I am running in automatic conversion mode, but this can happen when that isn't configured.

Could you provide guidence on why this could be happening?

5 months ago

0 Joel Meraz 5 months ago

TI__Mastermind 21150 points

Hi Stephen,

Are you able to share a logic analyzer capture of the described behavior? I have not come across this issue in the past, but if one device is showing different behavior to another, that would be important to investigate.

Regards,
Joel

0 Stephen Goodman 5 months ago in reply to Joel Meraz

Prodigy 10 points

Sorry, just to clear something up, it isn't second ADC121C021 that's on the bus its a different device. I should've been more clear about that.

Its hard to get a capture of when it starts getting in the state as it seems completely random. I shall try though and get back to you.

0 Stephen Goodman 5 months ago in reply to Joel Meraz

Prodigy 10 points

Here is an image of the write that failed.

This is the traffic leading up to the failure.

This is all three messages so you can see the timing.

I'm finding it difficult to trigger the scope to catch the failure, but this is what the I2C traffic looks like.
adcI2c.pdf

In case its important, this is the state of the registers before the first message.

adc121c02x : Reg: 0 = 0x017
adc121c02x : Reg: 1 = 0x002
adc121c02x : Reg: 2 = 0x034
adc121c02x : Reg: 3 = 0x000
adc121c02x : Reg: 4 = 0x007
adc121c02x : Reg: 5 = 0x000
adc121c02x : Reg: 6 = 0x000
adc121c02x : Reg: 7 = 0x0A4