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- //DHT library for the ESP8266, a port from the Adafruit library for the Arduino
- //MIT license
- //written by IoT Pipe
- #include "dht22.h"
- #define MIN_INTERVAL 2000
- #define NUM_VALID_INPUT_PINS 8
- const uint32_t pin_mux[NUM_VALID_INPUT_PINS] = {PERIPHS_IO_MUX_GPIO0_U,PERIPHS_IO_MUX_GPIO2_U,PERIPHS_IO_MUX_GPIO4_U,PERIPHS_IO_MUX_GPIO5_U,PERIPHS_IO_MUX_MTDI_U,PERIPHS_IO_MUX_MTCK_U,PERIPHS_IO_MUX_MTMS_U,PERIPHS_IO_MUX_MTDO_U};
- const uint8_t pin_num[NUM_VALID_INPUT_PINS] = {0,2,4,5,12,13,14,15};
- const uint8_t pin_func[NUM_VALID_INPUT_PINS] = {FUNC_GPIO0, FUNC_GPIO2,FUNC_GPIO4,FUNC_GPIO5,FUNC_GPIO12,FUNC_GPIO13,FUNC_GPIO14,FUNC_GPIO15};
- float ICACHE_FLASH_ATTR convertCtoF(float c) {
- return c * 1.8 + 32;
- }
- float ICACHE_FLASH_ATTR convertFtoC(float f) {
- return (f - 32) * 0.55555;
- }
- static int ICACHE_FLASH_ATTR get_index(int pin)
- {
- int i = 0;
- for(i = 0; i < NUM_VALID_INPUT_PINS; i++)
- {
- if(pin==pin_num[i])
- {
- return i;
- }
- }
- return -1;
- }
- void ICACHE_FLASH_ATTR DHT_begin(void)
- {
- LOG_DEBUG("DHT BEGIN");
- // set up the pins!
- int index = get_index(_pin);
- gpio_init();
- PIN_FUNC_SELECT(pin_mux[index],pin_func[index]);
- //GPIO_OUTPUT_SET(_pin,1);
- GPIO_DIS_OUTPUT(_pin);
- PIN_PULLUP_EN(pin_mux[index]);
- // Using this value makes sure that millis() - lastreadtime will be >= MIN_INTERVAL right away. Note that this assignment wraps around, but so will the subtraction.
- _lastreadtime = -MIN_INTERVAL;
- }
- static bool read() {
- int index = get_index(_pin);
- // Check if sensor was read less than two seconds ago and return early to use last reading.
- //This is todo. The force argument overrides this logic. We can implement in ESP8266 with a timer.
- uint32 current = system_get_time();
- if ( current - _lastreadtime < 2000000 )
- {
- LOG_DEBUG_ARGS("2 seconds is required between polls, Its only been %d (ms)",(current-_lastreadtime) / 1000);
- return _lastresult;
- }
- _lastreadtime=current;
- // Reset 40 bits of received data to zero.
- data[0] = data[1] = data[2] = data[3] = data[4] = 0;
- // Send start signal. See DHT datasheet for full signal diagram:
- // http://www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf
- // Go into high impedence state to let pull-up raise data line level and
- // start the reading process.
- GPIO_OUTPUT_SET(_pin,1);
- os_delay_us(250*1000);
- // First set data line low for 10 milliseconds.
- GPIO_OUTPUT_SET(_pin,0);
- os_delay_us(10*1000);
- uint32_t cycles[80];
- {
- // Turn off interrupts temporarily because the next sections are timing critical
- // and we don't want any interruptions.
- //TODO: We've disabled GPIO interrupts, but we haven't done anything about timers
- ETS_GPIO_INTR_DISABLE();
- // End the start signal by setting data line high for 40 microseconds.
- GPIO_OUTPUT_SET(_pin,1);
- os_delay_us(40);
- // Now start reading the data line to get the value from the DHT sensor.
- GPIO_DIS_OUTPUT(_pin);
- PIN_PULLUP_EN(pin_mux[index]);
- //os_delay_us(100); // Delay a bit to let sensor pull data line low.
- // First expect a low signal for ~80 microseconds followed by a high signal
- // for ~80 microseconds again.
- if (expectPulse(0) == 0)
- {
- LOG_DEBUG("Timeout waiting for start signal low pulse.");
- _lastresult = false;
- return _lastresult;
- }
- if (expectPulse(1) == 0)
- {
- LOG_DEBUG("Timeout waiting for start signal high pulse.");
- _lastresult = false;
- return _lastresult;
- }
- // Now read the 40 bits sent by the sensor. Each bit is sent as a 50
- // microsecond low pulse followed by a variable length high pulse. If the
- // high pulse is ~28 microseconds then it's a 0 and if it's ~70 microseconds
- // then it's a 1. We measure the cycle count of the initial 50us low pulse
- // and use that to compare to the cycle count of the high pulse to determine
- // if the bit is a 0 (high state cycle count < low state cycle count), or a
- // 1 (high state cycle count > low state cycle count). Note that for speed all
- // the pulses are read into a array and then examined in a later step.
- int i = 0;
- for (i=0; i<80; i+=2)
- {
- cycles[i] = expectPulse(0);
- cycles[i+1] = expectPulse(1);
- }
- } // Timing critical code is now complete.
- ETS_GPIO_INTR_ENABLE();
- // Inspect pulses and determine which ones are 0 (high state cycle count < low
- // state cycle count), or 1 (high state cycle count > low state cycle count).
- int i = 0;
- for (i=0; i<40; ++i)
- {
- uint32_t lowCycles = cycles[2*i];
- uint32_t highCycles = cycles[2*i+1];
- if ((lowCycles == 0) || (highCycles == 0))
- {
- LOG_DEBUG("Timeout waiting for pulse.");
- _lastresult = false;
- return _lastresult;
- }
- data[i/8] <<= 1;
- // Now compare the low and high cycle times to see if the bit is a 0 or 1.
- if (highCycles > lowCycles)
- {
- // High cycles are greater than 50us low cycle count, must be a 1.
- data[i/8] |= 1;
- }
- // Else high cycles are less than (or equal to, a weird case) the 50us low
- // cycle count so this must be a zero. Nothing needs to be changed in the
- // stored data.
- }
- LOG_DEBUG_ARGS("Received: %d,%d,%d,%d,%d ?= %d",data[0],data[1],data[2],data[3],data[4],(data[0] + data[1] + data[2] + data[3]) & 0xFF );
- // Check we read 40 bits and that the checksum matches.
- if (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF))
- {
- _lastresult = true;
-
- float f = data[0];
- f *= 256;
- f += data[1];
- f *= 0.1;
- f = data[2] & 0x7F;
- f *= 256;
- f += data[3];
- f *= 0.1;
- if (data[2] & 0x80) {
- f *= -1;
- }
- return _lastresult;
- }
- else
- {
- LOG_DEBUG("Checksum failure!");
- _lastresult = false;
- return _lastresult;
- }
- }
- // Expect the signal line to be at the specified level for a period of time and
- // return a count of loop cycles spent at that level (this cycle count can be
- // used to compare the relative time of two pulses). If more than a millisecond
- // ellapses without the level changing then the call fails with a 0 response.
- // This is adapted from Arduino's pulseInLong function (which is only available
- // in the very latest IDE versions):
- // https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/cores/arduino/wiring_pulse.c
- uint32_t expectPulse(bool level)
- {
- uint32_t count = 0;
- while (GPIO_INPUT_GET(_pin) == level)
- {
- if (count++ >= _maxcycles)
- {
- LOG_DEBUG_ARGS("Max cycles reached: %d",count);
- return 0; // Exceeded timeout, fail.
- }
- }
- return count;
- }
- void DHT_init(uint8_t pin, uint8_t type, uint8_t count)
- {
- LOG_DEBUG("DHT_INIT");
- _pin = pin;
- _type = type;
- //_maxcycles gives thenumber of cycles in a millisecond. this is used as a timeout in other functions.
- //bit11~bit0 are decimal part
- uint32_t cal = system_rtc_clock_cali_proc();
- uint32_t int_part = ((cal*1000) >> 12) / 1000;// + ( (float)(((cal*1000)>>12)%1000 ) / 1000.0f);
- uint32_t dec_part = ((cal * 1000) >> 12) % 1000;
- float result = int_part + (float)dec_part/1000.0f;
- _maxcycles = 1000.0f / result;
- LOG_DEBUG_ARGS("max cycles: %d",(int)_maxcycles);
- }
- float readHumidity()
- {
- float f = -1;
- if (read())
- {
- switch (_type)
- {
- case DHT11:
- f = data[0];
- break;
- case DHT22:
- case DHT21:
- f = data[0];
- f *= 256;
- f += data[1];
- f *= 0.1;
- break;
- }
- }
- return f;
- }
- //boolean S == Scale. True == Fahrenheit; False == Celcius
- float readTemperature(bool S) {
- float f = -1;
- if (read())
- {
- switch (_type)
- {
- case DHT11:
- f = data[2];
- if(S)
- {
- f = convertCtoF(f);
- }
- break;
- case DHT22:
- case DHT21:
- f = data[2] & 0x7F;
- f *= 256;
- f += data[3];
- f *= 0.1;
- if (data[2] & 0x80)
- {
- f *= -1;
- }
- if(S)
- {
- f = convertCtoF(f);
- }
- break;
- }
- }
- return f;
- }
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