143 lines
4.7 KiB
C
143 lines
4.7 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2016 Scott Shawcroft for Adafruit Industries
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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
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* all 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
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* THE SOFTWARE.
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*/
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#include "common-hal/analogio/AnalogIn.h"
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#include <string.h>
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#include "py/gc.h"
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#include "py/nlr.h"
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#include "py/runtime.h"
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#include "py/binary.h"
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#include "py/mphal.h"
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#include "shared-bindings/analogio/AnalogIn.h"
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#include "asf/sam0/drivers/adc/adc.h"
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#include "samd21_pins.h"
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// Number of active ADC channels.
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volatile uint8_t active_channel_count;
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// Shared between all the instances. Allocated only when needed.
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struct adc_module *adc_instance = NULL;
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struct adc_config *config_adc = NULL;
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void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
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const mcu_pin_obj_t *pin) {
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if (!pin->has_adc) {
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// No ADC function on that pin
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mp_raise_ValueError("Pin does not have ADC capabilities");
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}
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claim_pin(pin);
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self->pin = pin;
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if (adc_instance == NULL) {
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// Allocate strucs on the heap so we only use the memory when we
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// need it.
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adc_instance = gc_alloc(sizeof(struct adc_module), false);
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config_adc = gc_alloc(sizeof(struct adc_config), false);
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adc_get_config_defaults(config_adc);
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config_adc->reference = ADC_REFERENCE_INTVCC1;
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config_adc->gain_factor = ADC_GAIN_FACTOR_DIV2;
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config_adc->positive_input = self->pin->adc_input;
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config_adc->resolution = ADC_RESOLUTION_16BIT;
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config_adc->clock_prescaler = ADC_CLOCK_PRESCALER_DIV128;
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adc_init(adc_instance, ADC, config_adc);
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}
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self->adc_instance = adc_instance;
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self->config_adc = config_adc;
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active_channel_count++;
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}
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void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
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active_channel_count--;
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if (active_channel_count == 0) {
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adc_reset(adc_instance);
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gc_free(adc_instance);
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gc_free(config_adc);
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// Set our references to NULL so the GC doesn't mistakenly see the
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// pointers in memory.
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adc_instance = NULL;
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config_adc = NULL;
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}
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reset_pin(self->pin->pin);
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}
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void analogin_reset() {
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if (adc_instance != NULL) {
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adc_reset(adc_instance);
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adc_instance = NULL;
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}
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active_channel_count = 0;
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}
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uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
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// Something else might have used the ADC in a different way,
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// so we have to completely re-initialize it.
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// ADC must have been disabled before adc_init() is called.
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adc_init(adc_instance, ADC, config_adc);
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config_adc->positive_input = self->pin->adc_input;
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adc_enable(adc_instance);
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// Read twice and discard first result, as recommended in section 14 of
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// http://www.atmel.com/images/Atmel-42645-ADC-Configurations-with-Examples_ApplicationNote_AT11481.pdf
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// "Discard the first conversion result whenever there is a change in ADC configuration
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// like voltage reference / ADC channel change"
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// Empirical observation shows the first reading is quite different than subsequent ones.
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uint16_t data;
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enum status_code status;
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adc_start_conversion(adc_instance);
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do {
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status = adc_read(adc_instance, &data);
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} while (status == STATUS_BUSY);
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if (status == STATUS_ERR_OVERFLOW) {
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// TODO(tannewt): Throw an error.
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}
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adc_start_conversion(adc_instance);
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do {
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status = adc_read(adc_instance, &data);
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} while (status == STATUS_BUSY);
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if (status == STATUS_ERR_OVERFLOW) {
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// TODO(tannewt): Throw an error.
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}
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adc_disable(adc_instance);
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return data;
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}
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float common_hal_analogio_analogin_get_reference_voltage(analogio_analogin_obj_t *self) {
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return 3.3f;
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}
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