Arthur Roberts
45d7001bb0
got better results that passed checksum. NO idea why - I guess just being less "strict" on what the high / low period was
138 lines
3.6 KiB
C
138 lines
3.6 KiB
C
#include "dht22.h"
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#include "esp_log.h"
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#include "hal/gpio_types.h"
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#include "sdkconfig.h"
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#include "driver/gpio.h"
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#include <rom/ets_sys.h>
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#include "esp_timer.h"
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#include "freertos/portmacro.h"
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#define DATA_GPIO CONFIG_DHT22_DATA_GPIO
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#if DATA_GPIO == -1
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#error "Please define your DHT22 GPIO Data Pin"
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#endif /* CONFIG_DHT22_DATA_GPIO == -1 */
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static const char *TAG = "DHT22";
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deci_percent _dht22_relative_humidity = UINT16_MAX;
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deci_degrees_c _dht22_temperature = INT16_MIN;
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void dht22_handle_error(dht22_error e) {
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if (e == DHT22_OK) {
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ESP_LOGI(TAG, "No errors reading DHT22 value");
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} else if (e == DHT22_CHECKSUM_ERROR) {
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ESP_LOGE(TAG, "Error calculating checksum");
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} else if (e == DHT22_TIMING_ERROR) {
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ESP_LOGE(TAG, "Timing error while obtaining data");
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} else if (e == DHT22_TIMEOUT_ERROR) {
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ESP_LOGE(TAG, "Timeout error - waited >2ms for signal to change");
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} else {
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ESP_LOGE(TAG, "Unknown error: %i", e);
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}
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}
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uint32_t wait_for_signal_to_change_from(int signal_level) {
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uint64_t start_time = esp_timer_get_time();
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uint64_t next_time = start_time;
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/*
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A vague attempt at "waiting" until the pin comes some kind of level
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if (gpio_get_level(CONFIG_DHT22_DATA_GPIO) != signal_level) {
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ets_delay_us(15);
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}
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*/
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while (gpio_get_level(DATA_GPIO) == signal_level) {
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next_time = esp_timer_get_time();
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ets_delay_us(2); // just incase of lagging/debouncing/jitter/whatever
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if ((next_time - start_time) >= 1000 * 10) {
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return DHT22_TIMEOUT_ERROR;
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}
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}
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uint32_t elapsed_time = next_time - start_time;
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if (elapsed_time == 0) {
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return 1000;
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}
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return elapsed_time;
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}
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dht22_error dht22_read() {
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uint32_t elapsed_time;
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portDISABLE_INTERRUPTS();
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/*
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* From datasheet:
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* - Host pulls low "beyond at least 1ms"
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* - Host pulls up 20us to 40us
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*/
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gpio_set_direction(DATA_GPIO, GPIO_MODE_OUTPUT);
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gpio_set_level(DATA_GPIO, 0);
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ets_delay_us(5000);
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gpio_set_level(DATA_GPIO, 1);
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ets_delay_us(25);
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/*
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* From datasheet:
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* - DHT pulls low 80us
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* - DHT pulls high 80us
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*/
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gpio_set_direction(DATA_GPIO, GPIO_MODE_INPUT);
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// Maybe wait here until it goes high?
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while (gpio_get_level(DATA_GPIO) == 1) {
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// wait for a while - should only be 20 uS
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}
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elapsed_time = wait_for_signal_to_change_from(0);
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if (elapsed_time < 70 || elapsed_time > 90) {
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return DHT22_TIMING_ERROR;
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}
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elapsed_time = wait_for_signal_to_change_from(1);
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if (elapsed_time < 70 || elapsed_time > 90) {
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return DHT22_TIMING_ERROR;
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}
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/*
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* From datasheet:
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* - DHT pulls low 50us -> into to next bit
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* - DHT pulls high:
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* - if 26-28us -> 0 bit
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* - if 70us -> 1 bit
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*/
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uint8_t data[5] = {0, 0, 0, 0, 0};
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for (uint8_t i = 0; i < 40; i++) {
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elapsed_time = wait_for_signal_to_change_from(0);
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if (elapsed_time == DHT22_TIMEOUT_ERROR || elapsed_time < 30 || elapsed_time > 70) {
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return DHT22_TIMEOUT_ERROR;
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}
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elapsed_time = wait_for_signal_to_change_from(1);
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if (elapsed_time > 50) {
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data[i / 8] |= (1 << (7 - (i % 8)));
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}
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}
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portENABLE_INTERRUPTS();
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_dht22_relative_humidity = (data[0] << 8) | data[1];
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_dht22_temperature = ((data[2] & 0x7f) << 8) | data[3];
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if (data[2] & 0x80) {
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_dht22_temperature = -1 * _dht22_temperature;
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}
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uint8_t checksum_val = (data[0] + data[1] + data[2] + data[3]) & 0xff;
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if (checksum_val != data[4]) {
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_dht22_relative_humidity = UINT16_MAX;
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_dht22_temperature = INT16_MIN;
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return DHT22_CHECKSUM_ERROR;
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}
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return DHT22_OK;
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}
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deci_percent dht22_relative_humidity() { return _dht22_relative_humidity; }
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deci_degrees_c dht22_temperature() { return _dht22_temperature; }
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