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Asked: October 9, 2023In:
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Hello,Issue Description In nonstop mode scan of a 12-bit ADC on a Renesas RA6.I’ve configured 4 ADC channels ANxx0 to ANxx3. However, I have left ANxx1 to ANxx3 open and provided input to the ANxx0 pin. In this configuration, when ...Read more

Hello,

Issue Description In nonstop mode scan of a 12-bit ADC on a Renesas RA6.

I’ve configured 4 ADC channels ANxx0 to ANxx3. However, I have left ANxx1 to ANxx3 open and provided input to the ANxx0 pin. In this configuration, when I observe the ADC results, ANxx1 to ANxx3 display the count values or scan values of ANxx0, which is unanticipated.

This behavior indicates that ANxx1 to ANxx3 are showing the values of ANxx0 indeed though they’re open and should ideally display zero or some other default value.

Alternate, provided the input to ANxx2 pin that time ANxx0 and AN001 show the value between 0 to 30 (floating value this value is okay) but ANxx2 and ANxx3 show the near value indeed ANxx3 open.

Why this happened?

Is there any setting nonstop scan mode to set the open ANxxx port to zero?
Are there any h/ w changes need to do?

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ANxx0ANxx1ANxx2ANxx3Renesas RA6
  1. Julian White

    Hello, Thanks for reaching out to the Volt Tech Community. This action isn't unexpected it's quite normal. Because there's alone one sample and hold circuit, in nonstop scan mode if one channel is floating, the voltage of the next channel will still be present on the capacitor of the sample and holdRead more

    Hello,

    Thanks for reaching out to the Volt Tech Community.

    This action isn’t unexpected it’s quite normal.

    Because there’s alone one sample and hold circuit, in nonstop scan mode if one channel is floating, the voltage of the next channel will still be present on the capacitor of the sample and hold circuit.

    In general, it isn’t recommended to leave analog pins floating as their results are invalid.

    However, if you leave them open you can use the A/D Disposition Discovery Control Register. With this functionality, between the conversion of each channel, the capacitor of each channel will be discharged and near 0.

    The further states for discharge, the further discharge will be.

    ->ADDISCR_b. ADNDIS = 0xF;/ * Set the maximum number of states for discharge */

    ->ADDISCR_b. CHARGE = 0;/ * select Discharge */

    I hope it helps.

    Regards

    Jullian White

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