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TMP468: OFFSET REGISTER GARBAGE VALUES.

ROHIT R
Prodigy 80 points
Part Number: TMP468


Hi,

We are using fTMP468 for one of out designs. We are havig 2 I2C buses and we are using 2 sensors in I2C0 and 1 sensor in I2C1.

While reading the temperature, we have found that one of the sensor in I2C0 is showing large variation in values(that too negative values) and the rest of the sensors are reading fine.

Whiel checking the offset registor for the temperature sensor, we found the value as 0x00c0 as opposed to the required 0x0000 value.

All the registers were locked as the value in the C4 addressed register was 0x5CA6.

Even after setting the offset register value to 0x0000, it is changing automatically after sometime.

Kindly suggest the methods to debug the same.

  • 0
    TI__Genius 10810 points

    Hello Rohit,

    Thank you for providing this concern. When setting the offset register to 0x0000, did you unlock the C4 register? The TMP468 device powers up in locked mode, so the registers must be unlocked before any new data writes. Can you provide the logic analyzer captures for the one sensor in I2C0 and the schematic? This will help us to troubleshoot any potential communication and connection issues.

    Best Regards,

    Meredith McKean

  • 0 in reply to Meredith McKean
    Prodigy 80 points

    Hi Meredith,

    We are setting the resister value but unlocking the register itself. But my doubt is on what grounds are these offset register values changing automatically, is it expected so.

    As far as I have read, these offset registers are to be set from the user end but these values are changing automatically.

    What are the possibilities for the same, kindly suggest

  • 0 in reply to ROHIT R
    TI__Genius 10810 points

    Hello Rohit,

    Yes you are correct that the offset register is an user end input and should not change automatically. Please make sure you follow the commands in the order of Unlock, Write, and Lock. The only way to change the status of the register is to write to it. The device will reset on power cycle. Double check the pointer address. Is the device NACKing properly? Can you provide the logic analyzer captures for the one sensor in I2C0? This will help troubleshoot any potential communication issues. 

    Best Regards,

    Meredith McKean

  • 0 in reply to Meredith McKean
    Prodigy 80 points

    Hi Meredith,

    We shall provide you the Logic Analyzer captures at the earliest. Currently we have made a temporary setup as just before reading the temperature, we are writiing the offset registers to 0 in the order specified by you and we are getting correct temperatures. But Can you confirm how these register values change automatically as sometimes it is changing while the system is booting up and at times after the system is booted which shows us the non repeatability in the issue even.

    Can this registers be automatically written due to some hardware issue with the complete registers locked?

  • 0 in reply to ROHIT R
    TI__Genius 10810 points

    Hello Rohit,

    The values should not change automatically and the offset register is an user end input. I'm glad the hear that you are reading correct temperature values. Unique market demanded for a locking mechanism and not because of a bug.

    Best Regards,

    Meredith McKean