circuitpython/ports/raspberrypi/common-hal/analogio/AnalogIn.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2021 Scott Shawcroft for Adafruit Industries
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "common-hal/analogio/AnalogIn.h"
#include "shared-bindings/analogio/AnalogIn.h"
#include "shared-bindings/microcontroller/Pin.h"
#include "py/runtime.h"
#include "supervisor/shared/translate.h"

#include "src/rp2_common/hardware_adc/include/hardware/adc.h"

#define ADC_FIRST_PIN_NUMBER 26
#define ADC_PIN_COUNT 4

void common_hal_analogio_analogin_construct(analogio_analogin_obj_t *self, const mcu_pin_obj_t *pin) {
    if (pin->number < ADC_FIRST_PIN_NUMBER || pin->number > ADC_FIRST_PIN_NUMBER + ADC_PIN_COUNT) {
        raise_ValueError_invalid_pin();
    }

    adc_init();

    adc_gpio_init(pin->number);

    claim_pin(pin);
    self->pin = pin;
}

bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
    return self->pin == NULL;
}

void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
    if (common_hal_analogio_analogin_deinited(self)) {
        return;
    }

    reset_pin_number(self->pin->number);
    self->pin = NULL;
}

uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
    adc_select_input(self->pin->number - ADC_FIRST_PIN_NUMBER);
    uint16_t value = adc_read();

    // Stretch 12-bit ADC reading to 16-bit range
    return (value << 4) | (value >> 8);
}

float common_hal_analogio_analogin_get_reference_voltage(analogio_analogin_obj_t *self) {
    // The nominal VCC voltage
    return 3.3f;
}