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ADS1262: Use of the calibration function of adc issue

Cherry Zhou
Mastermind 22235 points
Part Number: ADS1262

Follow the steps for the calibration command given in Section 9.4.9.8 as follows:

1. write INPMUX (24'h460067), configure the channel;

2. write the REFMUX (24'h4F0012), configure reference voltage;

3. write MODE0 (24'h430000)" , configure continuous conversion mode;

4. write MODE1 (24'h440000), configure the filtering method;

5. write "MODE2 (24'h450005)", configure the gain and rate;

6. Send the "START1" command;

7. Send System Bias Calibration Command "SYOCAL1";

8. wait for 1s;

9. start reading the data.

Expected Result: after waiting for 1s, the DRDY pin is pulled low and the calibration value is written to the calibration register. What should be read at this point is the value after subtracting the calibration value.

Actual Result: after waiting for 1s, DRDY pin is still high.

According to the manual, DRDY is high during calibration and the calibration is pulled low when complete. Now that DRDY is still high, the customer would like to know the possible reason.

Is there anything else to do before and after the calibration instruction is sent in the bad order?

Best Regards,

Cherry Zhou

  • 0
    TI__Mastermind 35221 points

    Hi Cherry,

    Does DRDY ever go low, if the customer waits long enough? Does the ADC operate correctly if you are just measuring a signal i.e. not during calibration, but during normal operation?

    Also, what data rate and filter setting is selected in steps 4 and 5?

    -Bryan

  • 0 in reply to Bryan Lizon86
    TI__Mastermind 22235 points

    Hi Bryan,

    Thanks for your reply!

    Bryan Lizon86 said:
    Does DRDY ever go low, if the customer waits long enough?

    The customer waited for about two or three minutes, and the DRDY was still high. This is much longer than the calibration given in the manual.

    Bryan Lizon86 said:
    Does the ADC operate correctly if you are just measuring a signal i.e. not during calibration, but during normal operation?

    The ADC operates correctly and the data is already read correctly. The customer just would like to explore the effects of the calibration function.

    Bryan Lizon86 said:
    what data rate and filter setting is selected in steps 4 and 5?

    Sin1 filter, Gain = 1, 50 SPS

    Thanks and expecting the updates.

    Best Regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 35221 points

    Hi Cherry,

    Can you provide logic analyzer data showing the command sequence that they issue for the SYOCAL1? If the ADC communication is otherwise working okay, it would seem like there is an issue with the way this specific command is being issued. Therefore it would help to see what is going on with all of the digital signals during this command: DIN, DOUT, SCLK, CS

    -Bryan