DHT11驱动

移植到AHL-GEC-IDE中适用的DHT11温湿度传感器驱动。

//tempRegression.h文件
///=====================================================================

#ifndef __ADC_TEMP_REGRESSION_H
#define __ADC_TEMP_REGRESSION_H


#include "mcu.h"
#include "user.h"

void begin();
uint32_t expectPulse(uint8_t level);
uint8_t read();
float readTemperature();
#endif

---

//tempRegression.c文件

#include "tempRegression.h"

#define  DHT_11  (PTB_NUM|13)   //GEC30
 #define MIN_INTERVAL 2000
 #define TIMEOUT 0xFFFFFFFF
  uint8_t data[5];
  uint16_t _pin=DHT_11;
  uint32_t _lastreadtime;
  uint32_t _maxcycles;
  uint8_t _lastresult = 0;
  uint8_t pullTime; // Time (in usec) to pull up data line before reading


void begin() {
  // set up the pins!
  gpio_init(_pin, GPIO_INPUT, 0);
  _maxcycles = 8000;
  _lastreadtime = millis() - MIN_INTERVAL;
  printf("DHT max clock cycles: ");
  pullTime = 55;
}


uint32_t expectPulse(uint8_t level) {

  uint32_t count = 0;

  while (gpio_get(_pin) == level) {
    if (count++ >= _maxcycles) {
      return TIMEOUT; // Exceeded timeout, fail.
    }
  }

  return count;
}


uint8_t read() {
  // Check if sensor was read less than two seconds ago and return early
  // to use last reading.
  uint32_t currenttime = millis();
  if (((currenttime - _lastreadtime) < MIN_INTERVAL)) {
    return _lastresult; // return last correct measurement
  }
  _lastreadtime = currenttime;

  // 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_init(_pin, GPIO_INPUT, 0);
  Delay_ms(1);//延时1毫秒

  // First set data line low for a period according to sensor type
  gpio_init(_pin, GPIO_OUTPUT, 0);
  gpio_set(_pin, 0);

	Delay_ms(20); // data sheet says at least 18ms, 20ms just to be safe//延时20毫秒


  uint32_t cycles[80];
  {
    // End the start signal by setting data line high for 40 microseconds.
    gpio_init(_pin, GPIO_INPUT, 0);

    // Delay a moment to let sensor pull data line low.
    Delay_us(pullTime);

    // Now start reading the data line to get the value from the DHT sensor.

    // First expect a low signal for ~80 microseconds followed by a high signal
    // for ~80 microseconds again.
    if (expectPulse(0) == TIMEOUT) {
      printf("DHT timeout waiting for start signal low pulse.");
      _lastresult = 0;
      return _lastresult;
    }
    if (expectPulse(1) == TIMEOUT) {
      printf("DHT timeout waiting for start signal high pulse.");
      _lastresult = 0;
      return _lastresult;
    }

  	for (uint32_t i = 0; i < 80; i += 2) {
      cycles[i] = expectPulse(0);
      cycles[i + 1] = expectPulse(1);
    }
  } // Timing critical code is now complete.

  // 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).
  for (uint32_t i = 0; i < 40; ++i) {
    uint32_t lowCycles = cycles[2 * i];
    uint32_t highCycles = cycles[2 * i + 1];
    if ((lowCycles == TIMEOUT) || (highCycles == TIMEOUT)) {
      printf("DHT timeout waiting for pulse.");
      _lastresult = 0;
      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.
  }

  printf("Received from DHT:");


  // Check we read 40 bits and that the checksum matches.
  if (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) {
    _lastresult = 1;
    return _lastresult;
  } else {
    printf("DHT checksum failure!");
    _lastresult = 0;
    return _lastresult;
  }
}

float readTemperature() {
  float f = NAN;

  if (read()) {
      f = data[2];
      if (data[3] & 0x80) {
        f = -1 - f;
      }
      f += (data[3] & 0x0f) * 0.1;
  }
  return f;
}