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adc: Add doc details about configure not needed before each read

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Angus Gratton 2018-03-27 10:46:11 +11:00 committed by Angus Gratton
parent 9ea38560ec
commit 4507b3fde6
1 changed files with 21 additions and 7 deletions
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28
components/driver/include/driver/adc.h
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@ -147,11 +147,15 @@ esp_err_t adc1_config_width(adc_bits_width_t width_bit);
esp_err_t adc_set_data_width(adc_unit_t adc_unit, adc_bits_width_t width_bit);
/**
* @brief Configure the ADC1 channel, including setting attenuation.
* @brief Set the attenuation of a particular channel on ADC1, and configure its
* associated GPIO pin mux.
*
* @note This function also configures the input GPIO pin mux to
* connect it to the ADC1 channel. It must be called before calling
* adc1_get_raw() for this channel.
* @note For any given channel, this function must be called before the first time
* adc1_get_raw() is called for that channel.
*
* @note This function can be called multiple times to configure multiple
* ADC channels simultaneously. adc1_get_raw() can then be called for any configured
* channel.
*
* 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.
@ -168,6 +172,15 @@ esp_err_t adc_set_data_width(adc_unit_t adc_unit, adc_bits_width_t width_bit);
*
* @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 attenuaton (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 channel ADC1 channel to configure
* @param atten Attenuation level
*
@ -178,13 +191,14 @@ esp_err_t adc_set_data_width(adc_unit_t adc_unit, adc_bits_width_t width_bit);
esp_err_t adc1_config_channel_atten(adc1_channel_t channel, adc_atten_t atten);
/**
* @brief Take an ADC1 reading on a single channel
* @brief Take an ADC1 reading from a single channel.
*
* @note Call adc1_config_width() before the first time this
* function is called.
*
* @note For a given channel, adc1_config_channel_atten(channel)
* must be called before the first time this function is called.
* @note For any given channel, adc1_config_channel_atten(channel)
* must be called before the first time this function is called. Configuring
* a new channel does not prevent a previously configured channel from being read.
*
* @param channel ADC1 channel to read
*