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83 lines
2.6 KiB
C
83 lines
2.6 KiB
C
/**
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* @file adc.c
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* @brief Implementation of the 12-bit ADC driver
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* @author Kevin Thomas
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* @date 2025
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*
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* MIT License
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*
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* Copyright (c) 2025 Kevin Thomas
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "adc.h"
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#include "pico/stdlib.h"
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#include "hardware/adc.h"
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#define ADC_VREF_MV 3300
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#define ADC_FULL_SCALE 4095
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static uint8_t active_channel = 0;
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/**
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* @brief Convert a raw 12-bit ADC value to millivolts
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*
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* Scales the raw value linearly against the 3.3 V reference.
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*
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* @param raw 12-bit ADC conversion result (0 - 4095)
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* @return uint32_t Equivalent voltage in millivolts (0 - 3300)
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*/
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static uint32_t _raw_to_mv(uint16_t raw) {
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return (uint32_t)raw * ADC_VREF_MV / ADC_FULL_SCALE;
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}
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/**
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* @brief Convert a raw temperature-sensor ADC value to degrees Celsius
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*
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* Applies the RP2350 datasheet formula:
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* T = 27 - (V - 0.706) / 0.001721
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*
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* @param raw 12-bit ADC result from the internal temperature sensor (channel 4)
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* @return float Die temperature in degrees Celsius
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*/
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static float _raw_to_celsius(uint16_t raw) {
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float voltage = (float)raw * 3.3f / (float)ADC_FULL_SCALE;
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return 27.0f - (voltage - 0.706f) / 0.001721f;
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}
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void adc_driver_init(uint32_t gpio, uint8_t channel) {
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active_channel = channel;
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adc_init();
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adc_gpio_init(gpio);
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adc_set_temp_sensor_enabled(true);
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adc_select_input(channel);
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}
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uint32_t adc_driver_read_mv(void) {
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return _raw_to_mv(adc_read());
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}
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float adc_driver_read_temp_celsius(void) {
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adc_select_input(4);
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float result = _raw_to_celsius(adc_read());
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adc_select_input(active_channel);
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return result;
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}
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