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Original question:

ADS122U04: ADS122U04 Continuous Conversion mode outputs zeros

ADS122U04: Data conversion Never Starts

Warren Greenway
Prodigy 70 points
Part Number: ADS122U04

I have been able to write to and read registers on the ADS122U04, but not read any data. The issue is that the DRDY bit in the Config 2 register is never set after I send 0x55 0x08 (START). If I setup the DRDY line in Config 4 ( 0x55 0x44 0x48 ), I never see the pin toggle, it simply stays high. Again, I can write and confirm the values for all registers without a problem, it just doesn't appear to respond to start. On the same note, the datasheet shows sending 0x55 0x48 0x48 in the examples, but there is no Configuration 8 register, nor is the purpose of this command ever explained. Suggestions?

  • 0
    TI__Guru** 113765 points
    Hi Warren,

    Let's start at the end of your questions first. The WREG command 0x48, has the most significant 4 bits as the opcode (0x40) and the second 4 bits is the register to be written. Note in section 8.5.3.6 of the ADS122U04 datasheet that the register is left shifted in the lower 4 bits by 1. A register write to register 0 is command 0x40, register 1 is 0x42, register 2 is 0x44, register 3 is 0x46 and register 4 is 0x48. So a command of 0x55 (synchronization word) 0x48 (write register 4) 0x48 (data) would set register 4 with the GPIO2 to an output and GPIO2 to function as a nDRDY function.

    So when reading or writing the configuration register 2, make sure the command is correct. A register read of register 2. would be a command 0x55 0x24.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Prodigy 70 points
    That may have been the most lucid, to the point, helpful answer I have possibly every received for any question. Thank you! I missed the 1 bit shift, actually, and once corrected was immediately receiving data. You deserve guac, chips, and a tall cold beer.