ESP32 lets the user choose from using Vref, Lookup Table, and Two-Point Calibration. In ESP32S2 only two-point calibration is supported. This commit support these changes in idf.
Closes https://github.com/espressif/esp-idf/issues/5455
This commit removes the lookup table mode due to inferior performance when compared
to linear mode under attenuation 0, 1 and 2. However small portions of the lookup table
are kept for the higher voltages of atten 3 (above ADC reading 2880). That voltage range
in atten 3 has non linear characteristics making the LUT performan better than linear mode.
This commit updates the esp_adc_cal ocmponent to support new calibration methods
which utilize calibratoin values stored in eFuse. This commit includes LUT mode
1. Support built-in ADC for I2S.
2. Modify code of ADC, made no change to the original APIs.
3. Add APIs in I2S:
esp_err_t i2s_set_adc_mode(adc_unit_t adc_unit, adc1_channel_t adc_channel);
4. Add I2S ADC/DAC example code.
5. add old-fashion definition to make it more compatible
6. replase spi_flash_ APIs with esp_partition_ APIs
7. add example of generating audio table from wav
8. change example sound
Added component containg API that is able to correct raw ADC readings
into a voltage in mV. Also provided a helper function that combines
the process of getting the raw ADC1 reading then converting it to a
voltage in mV. In doing so, the adc1_get_voltage() function of the ADC
driver has been deprecated. Instead there is now adc1_get_raw to obtain
the raw ADC1 reading, and adc1_to_voltage() that gets the raw reading
and converts all in one function. Functions using the deprecated
adc1_get_voltage() have also been updated to use adc1_get_raw().
Conversion is based on ADC characteristics. The characteristics are based
on the ADC's v_ref, herefore the appropriate structure and functions have
been provided to obtain the ADC characteristics.
The existing ADC driver has also been modified by adding a function to
route the internal ADC reference voltage to a GPIO allowing users to measure
it manually.
Relevant documentation has also been updated
