j3d1/esp-open-rtos
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

Merge pull request #159 from sheinz/fix/dht

Browse source 
DHT11/DHT22 sensor library fixed.
This commit is contained in:
Angus Gratton 2016-07-10 16:07:44 +10:00 committed by GitHub
commit 6915caf49c
3 changed files with 182 additions and 106 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

35
examples/dht_sensor/dht_sensor.c
View file

@ -2,6 +2,8 @@
*
* This sample code is in the public domain.
*/
#include <stdio.h>
#include <stdlib.h>
#include "espressif/esp_common.h"
#include "esp/uart.h"
#include "FreeRTOS.h"
@ -13,29 +15,30 @@
* to read and print a new temperature and humidity measurement
* from a sensor attached to GPIO pin 4.
*/
int const dht_gpio = 4;
uint8_t const dht_gpio = 4;
void dhtMeasurementTask(void *pvParameters)
{
int8_t temperature = 0;
int8_t humidity = 0;
int16_t temperature = 0;
int16_t humidity = 0;
// DHT sensors that come mounted on a PCB generally have
// pull-up resistors on the data pin. It is recommended
// to provide an external pull-up resistor otherwise...
gpio_set_pullup(dht_gpio, false, false);
// DHT sensors that come mounted on a PCB generally have
// pull-up resistors on the data pin. It is recommended
// to provide an external pull-up resistor otherwise...
gpio_set_pullup(dht_gpio, false, false);
while(1) {
while(1) {
if (dht_read_data(dht_gpio, &humidity, &temperature)) {
printf("Humidity: %d%% Temp: %dC\n",
humidity / 10,
temperature / 10);
} else {
printf("Could not read data from sensor\n");
}
if (dht_fetch_data(dht_gpio, &humidity, &temperature)) {
printf("Humidity: %i%% Temp: %iC\n", humidity, temperature);
} else {
printf("Could not read data from sensor...");
// Three second delay...
vTaskDelay(3000 / portTICK_RATE_MS);
}
// Three second delay...
vTaskDelay(3000 / portTICK_RATE_MS);
}
}
void user_init(void)

222
extras/dht/dht.c
View file

@ -6,23 +6,26 @@
*/
#include "dht.h"
#include "FreeRTOS.h"
#include "string.h"
#include "task.h"
#include "esp/gpio.h"
#include <espressif/esp_misc.h> // sdk_os_delay_us
#ifndef DEBUG_DHT
#define DEBUG_DHT 0
#endif
// DHT timer precision in microseconds
#define DHT_TIMER_INTERVAL 2
#define DHT_DATA_BITS 40
#if DEBUG_DHT
// #define DEBUG_DHT
#ifdef DEBUG_DHT
#define debug(fmt, ...) printf("%s" fmt "\n", "dht: ", ## __VA_ARGS__);
#else
#define debug(fmt, ...) /* (do nothing) */
#endif
/*
/*
* Note:
* A suitable pull-up resistor should be connected to the selected GPIO line
*
@ -32,17 +35,17 @@
*
*
* Initializing communications with the DHT requires four 'phases' as follows:
*
*
* Phase A - MCU pulls signal low for at least 18000 us
* Phase B - MCU allows signal to float back up and waits 20-40us for DHT to pull it low
* Phase C - DHT pulls signal low for ~80us
* Phase D - DHT lets signal float back up for ~80us
*
*
* After this, the DHT transmits its first bit by holding the signal low for 50us
* and then letting it float back high for a period of time that depends on the data bit.
* duration_data_high is shorter than 50us for a logic '0' and longer than 50us for logic '1'.
*
* There are a total of 40 data bits trasnmitted sequentially. These bits are read into a byte array
* There are a total of 40 data bits transmitted sequentially. These bits are read into a byte array
* of length 5. The first and third bytes are humidity (%) and temperature (C), respectively. Bytes 2 and 4
* are zero-filled and the fifth is a checksum such that:
*
@ -50,95 +53,144 @@
*
*/
/*
* @pin the selected GPIO pin
* @interval how frequently the pin state is checked in microseconds
* @timeout maximum length of time to wait for the expected pin state
* @expected_pin_state high (true) or low (false) pin state
* @counter pointer to external uint8_t for tallying the duration waited for the pin state
*/
bool dht_await_pin_state(uint8_t pin, uint8_t interval, uint8_t timeout, bool expected_pin_state, uint8_t * counter) {
for (*counter = 0; *counter < timeout; *counter+=interval) {
if (gpio_read(pin) == expected_pin_state) return true;
sdk_os_delay_us(interval);
/**
* Wait specified time for pin to go to a specified state.
* If timeout is reached and pin doesn't go to a requested state
* false is returned.
* The elapsed time is returned in pointer 'duration' if it is not NULL.
*/
static bool dht_await_pin_state(uint8_t pin, uint32_t timeout,
bool expected_pin_state, uint32_t *duration)
{
for (uint32_t i = 0; i < timeout; i += DHT_TIMER_INTERVAL) {
// need to wait at least a single interval to prevent reading a jitter
sdk_os_delay_us(DHT_TIMER_INTERVAL);
if (gpio_read(pin) == expected_pin_state) {
if (duration) {
*duration = i;
}
return true;
}
}
return false;
}
/*
*
*
* @pin the selected GPIO pin
* @humidity pointer to external int8_t to store resulting humidity value
* @temperature pointer to external int8_t to store resulting temperature value
*/
bool dht_fetch_data(int8_t pin, int8_t * humidity, int8_t * temperature) {
int8_t data[40] = {0};
int8_t result[5] = {0};
uint8_t i = 0;
uint8_t init_phase_duration = 0;
uint8_t duration_data_low = 0;
uint8_t duration_data_high = 0;
gpio_enable(pin, GPIO_OUT_OPEN_DRAIN);
taskENTER_CRITICAL();
/**
* Request data from DHT and read raw bit stream.
* The function call should be protected from task switching.
* Return false if error occurred.
*/
static inline bool dht_fetch_data(uint8_t pin, bool bits[DHT_DATA_BITS])
{
uint32_t low_duration;
uint32_t high_duration;
// Phase 'A' pulling signal low to initiate read sequence
gpio_write(pin, 0);
sdk_os_delay_us(20000);
gpio_write(pin, 1);
// Step through Phase 'B' at 2us intervals, 40us max
if (dht_await_pin_state(pin, 2, 40, false, &init_phase_duration)) {
// Step through Phase 'C ' at 2us intervals, 88us max
if (dht_await_pin_state(pin, 2, 88, true, &init_phase_duration)) {
// Step through Phase 'D' at 2us intervals, 88us max
if (dht_await_pin_state(pin, 2, 88, false, &init_phase_duration)) {
// Read in each of the 40 bits of data...
for (i = 0; i < 40; i++) {
if (dht_await_pin_state(pin, 2, 60, true, &duration_data_low)) {
if (dht_await_pin_state(pin, 2, 75, false, &duration_data_high)) {
data[i] = duration_data_high > duration_data_low;
}
}
}
taskEXIT_CRITICAL();
for (i = 0; i < 40; i++) {
// Read each bit into 'result' byte array...
result[i/8] <<= 1;
result[i/8] |= data[i];
}
if (result[4] == ((result[0] + result[1] + result[2] + result[3]) & 0xFF)) {
// Data valid, checksum succeeded...
*humidity = result[0];
*temperature = result[2];
debug("Successfully retrieved sensor data...");
return true;
} else {
debug("Checksum failed, invalid data received from sensor...");
}
} else {
debug("Initialization error, problem in phase 'D'...");
}
} else {
debug("Initialization error, problem in phase 'C'...");
}
} else {
debug("Initialization error, problem in phase 'B'...");
// Step through Phase 'B', 40us
if (!dht_await_pin_state(pin, 40, false, NULL)) {
debug("Initialization error, problem in phase 'B'\n");
return false;
}
taskEXIT_CRITICAL();
return false;
// Step through Phase 'C', 88us
if (!dht_await_pin_state(pin, 88, true, NULL)) {
debug("Initialization error, problem in phase 'C'\n");
return false;
}
// Step through Phase 'D', 88us
if (!dht_await_pin_state(pin, 88, false, NULL)) {
debug("Initialization error, problem in phase 'D'\n");
return false;
}
// Read in each of the 40 bits of data...
for (int i = 0; i < DHT_DATA_BITS; i++) {
if (!dht_await_pin_state(pin, 65, true, &low_duration)) {
debug("LOW bit timeout\n");
return false;
}
if (!dht_await_pin_state(pin, 75, false, &high_duration)){
debug("HIGHT bit timeout\n");
return false;
}
bits[i] = high_duration > low_duration;
}
return true;
}
/**
* Pack two data bytes into single value and take into account sign bit.
*/
static inline int16_t dht_convert_data(uint8_t msb, uint8_t lsb)
{
int16_t data;
#if DHT_TYPE == DHT22
data = msb & 0x7F;
data <<= 8;
data |= lsb;
if (msb & BIT(7)) {
data = 0 - data; // convert it to negative
}
#elif DHT_TYPE == DHT11
data = msb * 10;
#else
#error "Unsupported DHT type"
#endif
return data;
}
bool dht_read_data(uint8_t pin, int16_t *humidity, int16_t *temperature)
{
bool bits[DHT_DATA_BITS];
uint8_t data[DHT_DATA_BITS/8] = {0};
bool result;
gpio_enable(pin, GPIO_OUT_OPEN_DRAIN);
taskENTER_CRITICAL();
result = dht_fetch_data(pin, bits);
taskEXIT_CRITICAL();
if (!result) {
return false;
}
for (uint8_t i = 0; i < DHT_DATA_BITS; i++) {
// Read each bit into 'result' byte array...
data[i/8] <<= 1;
data[i/8] |= bits[i];
}
if (data[4] != ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) {
debug("Checksum failed, invalid data received from sensor\n");
return false;
}
*humidity = dht_convert_data(data[0], data[1]);
*temperature = dht_convert_data(data[2], data[3]);
debug("Sensor data: humidity=%d, temp=%d\n", *humidity, *temperature);
return true;
}
bool dht_read_float_data(uint8_t pin, float *humidity, float *temperature)
{
int16_t i_humidity, i_temp;
if (dht_read_data(pin, &i_humidity, &i_temp)) {
*humidity = (float)i_humidity / 10;
*temperature = (float)i_temp / 10;
return true;
}
return false;
}

31
extras/dht/dht.h
View file

@ -5,13 +5,34 @@
*
*/
#ifndef __DTH_H__
#ifndef __DHT_H__
#define __DHT_H__
#include "FreeRTOS.h"
#include <stdint.h>
#include <stdbool.h>
bool dht_wait_for_pin_state(uint8_t pin, uint8_t interval, uint8_t timeout, bool expected_pin_sate, uint8_t * counter);
bool dht_fetch_data(int8_t pin, int8_t * humidity, int8_t * temperature);
#define DHT11 11
#define DHT22 22
#endif
// Type of sensor to use
#define DHT_TYPE DHT22
/**
* Read data from sensor on specified pin.
*
* Humidity and temperature is returned as integers.
* For example: humidity=625 is 62.5 %
* temperature=24.4 is 24.4 degrees Celsius
*
*/
bool dht_read_data(uint8_t pin, int16_t *humidity, int16_t *temperature);
/**
* Float version of dht_read_data.
*
* Return values as floating point values.
*/
bool dht_read_float_data(uint8_t pin, float *humidity, float *temperature);
#endif // __DHT_H__