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DAC80502: I cannot confirm that the DAC is working because the register data doesn't match the datasheet, and the DAC doesn't seem to output anything I write.

Robb Foote
Prodigy 90 points
Part Number: DAC80502

Tool/software:

Hello,

Although I have used the DAC80502 in previous designs, I cannot confirm that it is working because the register data doesn't match the datasheet, and the DAC doesn't seem to output anything I write. The data in the DAC80502 registers when reset on a power cycle is:

DEVID Register (0x01): 0x1502 (Datasheet: 0x0215)
SYNC Register (0x02): 0x0003 (Datasheet: 0x0300)
CONFIG Register (0x03): 0x0002 (Datasheet: 0x0000)
GAIN Register (0x04): 0x0300 (Datasheet: 0x0003)
TRIGGER Register (0x05): 0x0000 (Datasheet: 0x0000)
BRDCAST Register (0x06): 0x0000 (Datasheet: 0x0000)
STATUS Register (0x07): 0x0100 (Datasheet: 0x0000)
DAC-A Data Register Field Descriptions (0x08): 0x0000 (Datasheet: 0x0000)
DAC-B Data Register Field Descriptions (0x09): 0x0000 (Datasheet: 0x0000)

A0 (pin 7) on the circuit is now connected to GND; this was missed when the device was being laid out.

I am starting to think that the data I was reading over I2C communications was reading the LSDB first and then the MSDB. Any help would be greatly appreciated.

  • 0
    Prodigy 90 points

    I've attached the circuit for our DAC80502 layout.

  • 0 in reply to Robb Foote
    TI__Mastermind 42203 points

    Hi Robb, 

    I would agree with you. It looks like your controller is interpreting the data with MSDB and LSDB swapped. You can confirm this by sharing an oscilloscope screenshot of the I2C readback from the DEVID register. 

    Reading left to right after the device address write with the R/W bit pulled to 1, the data would be 0b 0000 0010 0001 0101.

    We can also double check one of your writes. The data might also be clocking out in a weird order from your controller. Send a screenshot with a write and let me know what you were intending to write. 

    Best,

    Katlynne Jones