Feature esp32s2 adccal

[mennovf]

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Pull Request Details 📖

I'm working on implementing ADC calibration for the ESP32-S2. I've made some progress, specifically reading calibration values from eFuse. I followed the code path in IDF’s examples/peripherals/adc/oneshot_read/main/oneshot_read_main.c as a guide.

Still running into a few issues:

• init_code: The V1 eFuse lacks an init_code, so manual calibration is required, but I haven’t gotten it to work yet.

  • set_init_code didn’t do anything until @JurajSadel’s recent regi2c commits for the S2.

  • Right now, the manual calibration logic lives in AdcConfig::enable_pin_with_cal(). But this runs before the ADC peripheral is initialized. This means it will hang on while !ADCI::is_done() {} and just not work properly in general. Probably better to add a calibrate() method to AdcCalSource and call it from Adc::new() in a loop over the pins.

  • Manual calibration always reads 0 for me, even though post-calibration reads do register a signal. I tested this by copy-pasting the Adc::new init code into adc_calibrate to get past the init ordering issue. The idf's self-calibration init code is around 0x680.

• scheme_line_fitting from IDF: This calculates slope and y-intercept from eFuse or a self-cal step. The y-intercept is often positive, which makes it unusable with AdcCalBasic, since that applies correction before the scaling in AdcCalLine. Also, the example seems to use both init_code AND a full affine correction

• Cleanup

Description

Implement adc calibration for the esp32s2.

#1203 #326

Testing

Some manual testing, not yet finished. I get the same efuse line calibration values as idf.