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ADS8866: ads8866

andre albagli
Prodigy 30 points
Part Number: ADS8866
Other Parts Discussed in Thread: RCV420

Tool/software:

Hi folks!!

I have 3 questions regarding this AD converter:

1) In the spec it says that the mininum clock frequency is 16MHz. Is it possible to use Raspberry Pi 4 to conect it via SPI ? 

2) Spec says that maximum voltage error is 4mV . I was thinking to use an analog multiplex to select one input for data channel and another one for zero voltage. After reading the zero voltageI would ajust the reading by subtracting the value from it . Is it a reasonable solution to correct the offset error?

3) Spec says that the maximum %FSR is 0.01. I use 5V as Vref , so the maximum error is 0,005v. So I'm planning to use the same multiplex and read this value and adjust all voltage readings. My question is: is it reasonable to do this way ?

Thanks!

Regards 

Andre

  • 0
    TI__Genius 9346 points

    Hi Andre,

    Thanks for your questions.

    1. Googling the max SPI clock for the Raspberry Pi 4, it seems to be about 125MHz, so it should be compatible. However, this depends on the exact Raspberry Pi model you plan to use. You may check its datasheet.
    2. Yes, this should be fine.
    3. I'm not sure I understand. Could you please elaborate?

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 30 points

    Samiha. Thanks a lot for your help.

    What I'm trying to do is to use a analog multiplex (either 8 or 16 inputs), feed it into RCV420 , a current to voltage converter from Texas and feed the ADC with an low pass filter. One of these inputs I was planning to measure de 5V or the final voltage range and adjust the gain by reading this data and adjusting all other channels. My question is related if this is a reasonable solution or if there is anything better I'm accepting sugestions.

    Thanks for your help!

    Andre

  • +1 in reply to andre albagli
    TI__Genius 9346 points

    Hi Andre,

    Yes, that should be okay. I am linking a video on how gain/offset calibration may be done: https://www.ti.com/video/5466249277001. Your method sounds similar and okay.

    Best regards,

    Samiha