64 lines
1.6 KiB
C
64 lines
1.6 KiB
C
/**
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* Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*
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*/
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#include <stdio.h>
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#include "pico/stdlib.h"
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#include "hardware/adc.h"
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/* Choose 'C' for Celsius or 'F' for Fahrenheit. */
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#define TEMPERATURE_UNITS 'C'
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/* References for this implementation:
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* raspberry-pi-pico-c-sdk.pdf, Section '4.1.1. hardware_adc'
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* pico-examples/adc/adc_console/adc_console.c */
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float read_onboard_temperature(const char unit) {
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/* 12-bit conversion, assume max value == ADC_VREF == 3.3 V */
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const float conversionFactor = 3.3f / (1 << 12);
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float adc = (float)adc_read() * conversionFactor;
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float tempC = 27.0f - (adc - 0.706f) / 0.001721f;
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if (unit == 'C') {
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return tempC;
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} else if (unit == 'F') {
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return tempC * 9 / 5 + 32;
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}
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return -1.0f;
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}
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int main() {
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stdio_init_all();
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#ifdef PICO_DEFAULT_LED_PIN
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gpio_init(PICO_DEFAULT_LED_PIN);
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gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
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#endif
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/* Initialize hardware AD converter, enable onboard temperature sensor and
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* select its channel (do this once for efficiency, but beware that this
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* is a global operation). */
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adc_init();
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adc_set_temp_sensor_enabled(true);
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adc_select_input(4);
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while (true) {
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float temperature = read_onboard_temperature(TEMPERATURE_UNITS);
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printf("Onboard temperature = %.02f %c\n", temperature, TEMPERATURE_UNITS);
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#ifdef PICO_DEFAULT_LED_PIN
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gpio_put(PICO_DEFAULT_LED_PIN, 1);
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sleep_ms(10);
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gpio_put(PICO_DEFAULT_LED_PIN, 0);
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#endif
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sleep_ms(990);
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}
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return 0;
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}
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