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ADS1220 Zero Calibration Offset

john normand
Prodigy 20 points
Other Parts Discussed in Thread: ADS1220

Hello,

I'm using the ads1220 connected in a ratiometric configuration. Exc+ 5 vdc. My configuration matches the specification sheet. I also configure all four registers like the spec sheet which uses the PSW switch to power the bridge. My question regards my startup routine, which configures the registers except for config register 0 (MUX). I set this register to 1110b (AINP and AINN shorted to (AVDD + AVSS) / 2). I send the start cmd and read the output in continuous conversion mode as if  I were reading the bridge normally. However, the output does not change and does not seem to be logically correct. Is there another configuration during this calibration process? Reg settings starting are 0 are: EEh, 04h, 98h, 00h for calibration.

Any help would be appreciated.

John

  • 0
    TI__Guru** 113765 points
    Hi John,

    Welcome to the E2E forum! Your configuration appears correct. The output result should be around 0, but remember that the output is binary 2's complement so a reading such as 0xFFFFFF is actually a -1 in decimal.

    What are the values you are seeing? Do you have scope or logic analyzer shots that you can share showing the reading of the conversion results? Are you using the RDATA command or are you reading the output directly (by sending 24 SCLKs)? Are you polling DRDY? Or are you using an interrupt (falling edge of DRDY) to trigger your read of results?

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    TI__Guru** 113765 points
    Hi John,

    I haven’t heard back from you, so I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)

    Best regards,
    Bob B