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docs: Correct ADC default resolution statement for ESP32-S2 #11653

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@eMUQI eMUQI commented Jul 27, 2025

Description of Change

This PR corrects the documentation for analogReadResolution by removing an incorrect statement that the ESP32-S3 default ADC resolution is 13 bits.

As confirmed by the function's own documentation in the core header file esp32-hal-adc.h, the default resolution for analogRead is 12 bits (producing a range of 0-4095).

Tests scenarios

Compiled and run on Seeed Studio XIAO ESP32S3 in version v3.3.0. By running the standard AnalogReadSerial example code, confirmed that the default output range is 0-4095, corresponding to 12-bit resolution.

Related links

https://docs.espressif.com/projects/arduino-esp32/en/latest/api/adc.html#analogreadresolution

arduino-esp32/cores/esp32/esp32-hal-adc.h

Lines 49 to 56 in c7520cc

/*
* Set the resolution of analogRead return values. Default is 12 bits (range from 0 to 4096).
* If between 9 and 12, it will equal the set hardware resolution, else value will be shifted.
* Range is 1 - 16
*
* Note: compatibility with Arduino SAM
*/
void analogReadResolution(uint8_t bits);

https://github.com/espressif/esp-idf/blob/346870a3044010f2018be0ef3b86ba650251c655/components/soc/esp32s3/include/soc/soc_caps.h#L129-L130

@eMUQI eMUQI requested a review from pedrominatel as a code owner July 27, 2025 12:13
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@lucasssvaz lucasssvaz requested a review from P-R-O-C-H-Y July 27, 2025 16:07
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P-R-O-C-H-Y requested changes Jul 28, 2025
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Hi @eMUQI, I have checked the code and you are right about the S3. The documentation should say that for S2! Can you please instead of removing it change the S3 to S2? Thanks

@P-R-O-C-H-Y P-R-O-C-H-Y added the Type: Documentation Issue pertains to Documentation of Arduino ESP32 label Jul 28, 2025
@eMUQI eMUQI changed the title docs: Remove incorrect statement on ESP32-S3 default resolution docs: Correct ADC default resolution statement for ESP32-S2 Jul 28, 2025
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eMUQI commented Jul 28, 2025

Hi @P-R-O-C-H-Y , thanks for the review and clarification!
I've updated the PR as you suggested. Could you please take another look?

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LGTM

@P-R-O-C-H-Y P-R-O-C-H-Y added the Status: Pending Merge Pull Request is ready to be merged label Jul 28, 2025
pedrominatel
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docs/en/api/adc.rst Outdated
@@ -52,7 +52,8 @@ This function will return analog value in millivolts (calibrated).
analogReadResolution
^^^^^^^^^^^^^^^^^^^^

This function is used to set the resolution of ``analogRead`` return value. Default is 12 bits (range from 0 to 4095).
This function is used to set the resolution of ``analogRead`` return value. Default is 12 bits (range from 0 to 4095)
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This is only for the chip revision v0.0. For v1.0, the resolution is 12 bits.

Please add a reference to the ADC-112 Bit 1 of SAR ADC Does Not Flip errata.

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Hi @eMUQI, can you take a look?

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Hi @pedrominatel,
Thanks for the clarification. Just to make sure I understand correctly:
The documentation should specify that the 13-bit default resolution only applies to ESP32-S2 chip revision v0.0, and I should also add a reference to the ADC-112 Bit 1 of SAR ADC Does Not Flip errata.
Is that correct? If so, I will update the PR accordingly.
Thanks!

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That's right.

@lucasssvaz lucasssvaz removed the Status: Pending Merge Pull Request is ready to be merged label Jul 28, 2025
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eMUQI commented Jul 30, 2025

@pedrominatel I've pushed the requested changes. PTAL when you have a moment. Thanks!

image

@pedrominatel pedrominatel added the Status: Pending Merge Pull Request is ready to be merged label Jul 31, 2025
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