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doc/adc: modifications in the adc documentation and adc headers

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Wu Bo Wen
2020-07-15 11:19:29 +08:00
committed by bot
parent 5c5c7c4449
commit 658b56a690
4 changed files with 187 additions and 185 deletions
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30
components/hal/esp32/include/hal/adc_ll.h
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@@ -452,36 +452,6 @@ static inline void adc_ll_set_sar_clk_div(adc_ll_num_t adc_n, uint32_t div)
/**
* Set the attenuation of a particular channel on ADCn.
*
* @note For any given channel, this function must be called before the first time conversion.
*
* The default ADC full-scale voltage is 1.1V. To read higher voltages (up to the pin maximum voltage,
* usually 3.3V) requires setting >0dB signal attenuation for that ADC channel.
*
* When VDD_A is 3.3V:
*
* - 0dB attenuation (ADC_ATTEN_DB_0) gives full-scale voltage 1.1V
* - 2.5dB attenuation (ADC_ATTEN_DB_2_5) gives full-scale voltage 1.5V
* - 6dB attenuation (ADC_ATTEN_DB_6) gives full-scale voltage 2.2V
* - 11dB attenuation (ADC_ATTEN_DB_11) gives full-scale voltage 3.9V (see note below)
*
* @note The full-scale voltage is the voltage corresponding to a maximum reading (depending on ADC1 configured
* bit width, this value is: 4095 for 12-bits, 2047 for 11-bits, 1023 for 10-bits, 511 for 9 bits.)
*
* @note At 11dB attenuation the maximum voltage is limited by VDD_A, not the full scale voltage.
*
* Due to ADC characteristics, most accurate results are obtained within the following approximate voltage ranges:
*
* - 0dB attenuation (ADC_ATTEN_DB_0) between 100 and 950mV
* - 2.5dB attenuation (ADC_ATTEN_DB_2_5) between 100 and 1250mV
* - 6dB attenuation (ADC_ATTEN_DB_6) between 150 to 1750mV
* - 11dB attenuation (ADC_ATTEN_DB_11) between 150 to 2450mV
*
* For maximum accuracy, use the ADC calibration APIs and measure voltages within these recommended ranges.
*
* @param adc_n ADC unit.
* @param channel ADCn channel number.
* @param atten The attenuation option.
*/
static inline void adc_ll_set_atten(adc_ll_num_t adc_n, adc_channel_t channel, adc_atten_t atten)
{