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DAC5571 read back problem

Steve Hudson
Prodigy 140 points
Other Parts Discussed in Thread: DAC5571, DAC8571

I am writing to the DAC5571 and then performing a read back to verify the value was written correctly. There is about 1 ms between the write and read operation. However, I get a NAK whenever I transmit the device address with the READ bit. Why am I getting a NAK? I am using the low speed I2C mode.

  • 0
    TI__Mastermind 46290 points

    Steve,

    Can you post an oscilloscope capture of this bus activity along with your address settings? If you want to provide a schematic as well that is welcome.

  • 0 in reply to Kevin Duke
    Prodigy 140 points

    The address is set to 0x4C. Attached are screen shots of the DAC write and subsequent read. Please note that the read cycle results in a NAK, so there is no further transmission after this point. The time between the write and read cycle is ~1ms.

    WRITE CYCLE

    READ CYCLE

  • 0 in reply to Steve Hudson
    TI__Mastermind 46290 points

    Steve,

    There doesn't look to be anything wrong with your I2C communication. Typically I2C is a pretty difficult interface to make mistakes on short of the addressing + R/W byte for some folks. I am a little skeptical of if this device actually supports a read function since there isn't any explicit mention of it in the datasheet. If we look at it's "big brother" the DAC8571 does explicitly call out read-back capabilities. 

    Give me some time to find and dig into the design files for the DAC5571 to confirm or deny this hunch.

  • 0 in reply to Kevin Duke
    Prodigy 140 points

    OK, thanks for looking into this.

  • 0 in reply to Steve Hudson
    TI__Mastermind 46290 points

    Steve,

    Sorry for the delays. I looked into the design files for quite some time but due to the age of the design some components of the digital design are incomplete. I've tried reading from the device with a pretty well vetted I2C bus and I see the same results that you have shown here.

    Based on my findings, I do not believe that this device supports and I2C read. I will continue trying a few other things but I'm pretty well convinced that there is no read function.

  • 0 in reply to Kevin Duke
    Prodigy 140 points

    Kevin,

    Thanks for looking into this. I've released the product based upon the assumption that I cannot read back.

    Regards,

    Steve