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ADS124S06: Output data

Daisuke Higa
Genius 4765 points

Part Number: ADS124S06
Other Parts Discussed in Thread: ADS124S08,

Hi support team all.

Could you help me from our customer? 

 The initial command sequence is as follows:

INPMUX 10

PGA 08

DATARATE 14

REF 12

IDACMAG 07

IDACMUX 76

VBIAS 00

SYS 18

CFCAL0 DA

OFCAL1 0B

------------------------------------------

<Inquiry>

The data after calibration is 0xFFFFDA=-38

After calibration, CFCAL0 and CFCAL1 were written, and the value after calibration became 0xFF0BDA=-62502. and so on. 

After this, when input AINx was connected to GND, the output count became 488.

I don't know why it became this value. Could you help me understand it? 

Best regards,

DH

  • 0
    TI__Mastermind 49215 points

    Hi Daisuke Higa，

    The steps you described confused me.

    The data after calibration is 0xFFFFDA=-38 ->What's the analog input when you get -38 output code? What's the value in CFCAL0 and CFCAL1 registers?

    After calibration, CFCAL0 and CFCAL1 were written, and the value after calibration became 0xFF0BDA=-62502. and so on. -> Did the customer write CFCAL0 and CFCAL1 registers for calibration? or did they write those registers after the calibration? What's the analog input and the value in CFCAL0 and CFCAL1 registers when the customer got this 0xFF0BDA code?

    After this, when input AINx was connected to GND, the output count became 488.-> Do you mean the output code for grounded input is 488 after the offset calibration? Is the power supply for ADS124S08 is unipolar 5V (AVDD=5V and AVSS=0V)?

    BR,

    Dale

  • 0 in reply to Dale Li
    Genius 4765 points

    Hi Dale-san

    Thank you for your reply.

    I wrote inline in blue. 

    The data after calibration is 0xFFFFDA=-38 

    ->What's the analog input when you get -38 output code? What's the value in OFCAL0 and OFCAL1 registers?

    ->Analog input is connected to GND. OFCAL0&1&2 = 00h.

    After calibration, OFCAL0 and OFCAL1 were written, and the value after calibration became 0xFF0BDA=-62502. and so on.

     -> Did the customer write OFCAL0 and OFCAL1 registers for calibration? or did they write those registers after the calibration? What's the analog input and the value in OFCAL0 and OFCAL1 registers when the customer got this 0xFF0BDA code?

    ->Analog input is connected to GND. OFCAL0&1&2 = 00h. They wrote after calibration.

    After this, when input AINx was connected to GND, the output count became 488.

    -> Do you mean the output code for grounded input is 488 after the offset calibration? Is the power supply for ADS124S08 is unipolar 5V (AVDD=5V and AVSS=0V)?

    ->Both are yes. 

    Best regards,

    DH

  • 0 in reply to Daisuke Higa
    TI__Guru 58701 points

    Hi Daisuke Higa,

    You must disable the PGA to measure a single-ended (GND) input using a unipolar supply (AVSS = 0V, AVDD = 5V). See section 9.3.2.3 in the ADS124S06 datasheet for more information

    If the customer shorts the ADC inputs together i.e. MUXP = MUXN = 0V, they should be able to issue the SYOCAL command to determine the system offset. Note that using the SYOCAL command automatically updates the OFCAL registers

    If the customer issues the SFOCAL command then the ADC automatically shorts the inputs together internal to the ADC (after the mux, before the PGA) to determine the PGA+ADC offset. Note that using the SFOCAL command automatically updates the OFCAL registers

    I am not sure why the customer is manually writing to the OFCAL registers or why the result is changing: "The data after calibration is 0xFFFFDA=-38", "After calibration, CFCAL0 and CFCAL1 were written, and the value after calibration became 0xFF0BDA=-62502" <-- why are there two different values here?

    -Bryan