• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 45 subscribers
  • Views 365 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADC121C021 Read Problem

Chris Strahm
Prodigy 20 points


Just tried using this ADC in a design, but the MCU (LPC1765) I2C does not seem to work with this chip.  I ran a logic trace, and while the ADC responds with a ACK to the SLA Write address, it responds with a NAK to the same SLA+R byte.   No question about it, either the edges of the MCU SCL/SDA pulses are not right for this chip, or something is wrong with the I2C interface of the chip.  The waveforms look textbook.  I am trying to read 2 bytes (16b) from any of the 16b regs.  None of them read back, as the ADC fails to ACK the initial send of the SLA+R byte.  Yet it responds (ACKs) with writes to the same SLA address.  I give up,  changing to a different ADC.

  • 0
    Prodigy 20 points

    Trying to get meaningful data our of this, but it acts crazy.  I have a logic analyzer on this as well.

    I get 0xFFFF out of the conv reg, but the doc says the top 4 bits are suppose to be always 0.

    How is that possible?

    Then I set the ALERT reg to 0x03 to clear the Alert flags, and then I get 0xF030 reading the conv reg.

    Also, when I set the Lo/HI limit regs to 0x0000 or 0x0FFF and then read them back,

    I get wacky LO values like 0x000F .  I didn't set that value.

    I keep getting crazy readings from this ADC.  

    What is the magic way to get this thing to just produce real conv data?