gem_adc.h

/*
    Copyright (c) 2021 Alethea Katherine Flowers.
    Published under the standard MIT License.
    Full text available at: https://opensource.org/licenses/MIT
*/

#pragma once

/* Routines for interacting with the SAM D21 analog-to-digital converter. */

#include "fix16.h"
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

struct GemADCConfig {
    uint32_t gclk;
    uint32_t gclk_prescaler;
    uint32_t sample_time;
    uint32_t sample_num;
    uint32_t adjres;
};

/*
    Input channel descriptor. These settings should be derived from the
    pin multiplexing table in the datasheet.
*/
struct GemADCInput {
    /* IO port for the input */
    uint8_t port;
    /* Pin number for the input */
    uint32_t pin;
    /* AIN number for the input */
    uint32_t ain;
    /* Invert the value? */
    bool invert;
};

#define GEM_ADC_INPUT(port_, pin_, ain_)                                                                               \
    ((struct GemADCInput){WNTR_PORT_##port_, pin_, ADC_INPUTCTRL_MUXPOS_PIN##ain_, false})
#define GEM_ADC_INPUT_INVERTED(port_, pin_, ain_)                                                                      \
    ((struct GemADCInput){WNTR_PORT_##port_, pin_, ADC_INPUTCTRL_MUXPOS_PIN##ain_, true})

void gem_adc_init(const struct GemADCConfig* adc, int16_t offset_error, uint16_t gain_error);

/* Configure hardware error correction. */
void gem_adc_set_error_correction(uint16_t gain, uint16_t offset);

/* Configure a given input channel for ADC reading. */
void gem_adc_init_input(const struct GemADCInput* const input);

uint16_t gem_adc_read_sync(const struct GemADCInput* input);

/*
    Start scanning input channels using the ADC's result ready interrupt.
    The results array will be continously updated with new ADC readings.
    You can check when a complete set of readings is ready by calling
    gem_adc_results_ready().
*/
void gem_adc_start_scanning(const struct GemADCInput* inputs, size_t num_inputs, uint32_t* results);

void gem_adc_stop_scanning();
void gem_adc_resume_scanning();

/* Check if the channel scanning has finished scanning all channels. */
bool gem_adc_results_ready();