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Arduino Mega 2560 LESSON:12 DHT11 温度湿度センサー dht nonblocking.cpp - 版の履歴
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[[Arduino Mega 2560 LESSON:12 DHT11 温度湿度センサー]]に戻る。<br />
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<freescript></script><div class="hljs-wrap"><pre data-label="Arduino Code" class="pre-wrap"><br />
<code class="cpp">/*<br />
* DHT11, DHT21, and DHT22 non-blocking library.<br />
* Based on Adafruit Industries' DHT driver library.<br />
*<br />
* (C) 2015 Ole Wolf <wolf@blazingangles.com><br />
*<br />
* This program is free software: you can redistribute it and/or modify<br />
* it under the terms of the GNU General Public License as published by<br />
* the Free Software Foundation, either version 3 of the License, or<br />
* (at your option) any later version.<br />
*<br />
* This program is distributed in the hope that it will be useful,<br />
* but WITHOUT ANY WARRANTY; without even the implied warranty of<br />
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the<br />
* GNU General Public License for more details.<br />
*<br />
* You should have received a copy of the GNU General Public License<br />
* along with this program. If not, see <http://www.gnu.org/licenses/>.<br />
*/<br />
<br />
<br />
#include "dht_nonblocking.h"<br />
<br />
<br />
#define DHT_IDLE 0<br />
#define DHT_BEGIN_MEASUREMENT 1<br />
#define DHT_BEGIN_MEASUREMENT_2 2<br />
#define DHT_DO_READING 3<br />
#define DHT_COOLDOWN 4<br />
<br />
<br />
/* Number of milliseconds before a new sensor read may be initiated. */<br />
#define COOLDOWN_TIME 2000<br />
<br />
<br />
/*<br />
* Constructor for the sensor. It remembers the pin number and the<br />
* type of sensor, and initializes internal variables.<br />
*/<br />
DHT_nonblocking::DHT_nonblocking( uint8_t pin, uint8_t type )<br />
: _pin( pin ),<br />
_type( type ),<br />
_bit( digitalPinToBitMask( pin ) ),<br />
_port( digitalPinToPort( pin ) ),<br />
_maxcycles( microsecondsToClockCycles( 1000 ) )<br />
{<br />
dht_state = DHT_IDLE;<br />
<br />
pinMode( _pin, INPUT );<br />
digitalWrite( _pin, HIGH );<br />
}<br />
<br />
<br />
<br />
/*<br />
* Instruct the DHT to begin sampling. Keep polling until it returns true.<br />
* The tempearture is in degrees Celsius, and the humidity is in %.<br />
*/<br />
bool DHT_nonblocking::measure( float *temperature, float *humidity )<br />
{<br />
if( read_nonblocking( ) == true )<br />
{<br />
*temperature = read_temperature( );<br />
*humidity = read_humidity( );<br />
return( true );<br />
}<br />
else<br />
{<br />
return( false );<br />
}<br />
}<br />
<br />
<br />
<br />
float DHT_nonblocking::read_temperature( ) const<br />
{<br />
int16_t value;<br />
float to_return;<br />
<br />
switch( _type )<br />
{<br />
case DHT_TYPE_11:<br />
value = data[ 2 ];<br />
to_return = (float) value;<br />
break;<br />
<br />
case DHT_TYPE_21:<br />
case DHT_TYPE_22:<br />
value = ( data[ 2 ] & 0x7f ) << 8;<br />
value |= data[ 3 ];<br />
if( ( data[ 2 ] & 0x80 ) != 0 )<br />
{<br />
value = -value;<br />
}<br />
to_return = ( (float) value ) / 10.0;<br />
break;<br />
<br />
default:<br />
to_return = NAN;<br />
break;<br />
}<br />
<br />
return( to_return );<br />
}<br />
<br />
<br />
<br />
float DHT_nonblocking::read_humidity( ) const<br />
{<br />
uint16_t value;<br />
float to_return;<br />
<br />
switch( _type )<br />
{<br />
case DHT_TYPE_11:<br />
value = data[ 0 ];<br />
to_return = (float) value;<br />
break;<br />
<br />
case DHT_TYPE_21:<br />
case DHT_TYPE_22:<br />
value = data[ 0 ] << 8;<br />
value |= data[ 1 ];<br />
to_return = (float)value / 10.0;<br />
break;<br />
<br />
default:<br />
to_return = NAN;<br />
break;<br />
}<br />
<br />
return( to_return );<br />
}<br />
<br />
<br />
<br />
/*<br />
* Expect the input to be at the specified level and return the number<br />
* of loop cycles spent there. This is identical to Adafruit's blocking<br />
* driver.<br />
*/<br />
uint32_t DHT_nonblocking::expect_pulse(bool level) const<br />
{<br />
uint32_t count = 0;<br />
// On AVR platforms use direct GPIO port access as it's much faster and better<br />
// for catching pulses that are 10's of microseconds in length:<br />
#ifdef __AVR<br />
uint8_t portState = level ? _bit : 0;<br />
while ((*portInputRegister(_port) & _bit) == portState) {<br />
if (count++ >= _maxcycles) {<br />
return 0; // Exceeded timeout, fail.<br />
}<br />
}<br />
// Otherwise fall back to using digitalRead (this seems to be necessary on ESP8266<br />
// right now, perhaps bugs in direct port access functions?).<br />
#else<br />
while (digitalRead(_pin) == level) {<br />
if (count++ >= _maxcycles) {<br />
return 0; // Exceeded timeout, fail.<br />
}<br />
}<br />
#endif<br />
<br />
return count;<br />
}<br />
<br />
<br />
<br />
/*<br />
* State machine of the non-blocking read.<br />
*/<br />
bool DHT_nonblocking::read_nonblocking( )<br />
{<br />
bool status = false;<br />
<br />
switch( dht_state )<br />
{<br />
/* We may begin measuring any time. */<br />
case DHT_IDLE:<br />
dht_state = DHT_BEGIN_MEASUREMENT;<br />
break;<br />
<br />
/* Initiate a sensor read. The read begins by going to high impedance<br />
state for 250 ms. */<br />
case DHT_BEGIN_MEASUREMENT:<br />
digitalWrite( _pin, HIGH );<br />
/* Reset 40 bits of received data to zero. */<br />
data[ 0 ] = data[ 1 ] = data[ 2 ] = data[ 3 ] = data[ 4 ] = 0;<br />
dht_timestamp = millis( );<br />
dht_state = DHT_BEGIN_MEASUREMENT_2;<br />
break;<br />
<br />
/* After the high impedance state, pull the pin low for 20 ms. */<br />
case DHT_BEGIN_MEASUREMENT_2:<br />
/* Wait for 250 ms. */<br />
if( millis( ) - dht_timestamp > 250 )<br />
{<br />
pinMode( _pin, OUTPUT );<br />
digitalWrite( _pin, LOW );<br />
dht_timestamp = millis( );<br />
dht_state = DHT_DO_READING;<br />
}<br />
break;<br />
<br />
case DHT_DO_READING:<br />
/* Wait for 20 ms. */<br />
if( millis( ) - dht_timestamp > 20 )<br />
{<br />
dht_timestamp = millis( );<br />
dht_state = DHT_COOLDOWN;<br />
status = read_data( );<br />
// if( status != true )<br />
// {<br />
// Serial.println( "Reading failed" );<br />
// }<br />
}<br />
break;<br />
<br />
/* If it has been less than two seconds since the last time we read<br />
the sensor, then let the sensor cool down.. */<br />
case DHT_COOLDOWN:<br />
if( millis( ) - dht_timestamp > COOLDOWN_TIME )<br />
{<br />
dht_state = DHT_IDLE;<br />
}<br />
break;<br />
<br />
default:<br />
break;<br />
}<br />
<br />
return( status );<br />
}<br />
<br />
<br />
<br />
/* Read sensor data. This is identical to Adafruit's blocking driver. */<br />
bool DHT_nonblocking::read_data( )<br />
{<br />
uint32_t cycles[ 80 ];<br />
<br />
/* Turn off interrupts temporarily because the next sections are timing critical<br />
and we don't want any interruptions. */<br />
{<br />
volatile DHT_interrupt interrupt;<br />
<br />
// End the start signal by setting data line high for 40 microseconds.<br />
digitalWrite( _pin, HIGH );<br />
delayMicroseconds( 40 );<br />
<br />
// Now start reading the data line to get the value from the DHT sensor.<br />
pinMode( _pin, INPUT );<br />
// Delay a bit to let sensor pull data line low.<br />
delayMicroseconds( 10 );<br />
<br />
// First expect a low signal for ~80 microseconds followed by a high signal<br />
// for ~80 microseconds again.<br />
if( expect_pulse( LOW ) == 0 )<br />
{<br />
return( false );<br />
}<br />
if( expect_pulse( HIGH ) == 0 )<br />
{<br />
return( false );<br />
}<br />
<br />
// Now read the 40 bits sent by the sensor. Each bit is sent as a 50<br />
// microsecond low pulse followed by a variable length high pulse. If the<br />
// high pulse is ~28 microseconds then it's a 0 and if it's ~70 microseconds<br />
// then it's a 1. We measure the cycle count of the initial 50us low pulse<br />
// and use that to compare to the cycle count of the high pulse to determine<br />
// if the bit is a 0 (high state cycle count < low state cycle count), or a<br />
// 1 (high state cycle count > low state cycle count). Note that for speed all<br />
// the pulses are read into a array and then examined in a later step.<br />
for( int i = 0; i < 80; i += 2 )<br />
{<br />
cycles[ i ] = expect_pulse( LOW );<br />
cycles[ i + 1 ] = expect_pulse( HIGH );<br />
}<br />
<br />
/* Timing critical code is now complete. */<br />
}<br />
<br />
// Inspect pulses and determine which ones are 0 (high state cycle count < low<br />
// state cycle count), or 1 (high state cycle count > low state cycle count).<br />
for( int i = 0; i < 40; ++i )<br />
{<br />
uint32_t low_cycles = cycles[ 2 * i ];<br />
uint32_t high_cycles = cycles[ 2 * i + 1 ];<br />
if( ( low_cycles == 0 ) || ( high_cycles == 0 ) )<br />
{<br />
return( false );<br />
}<br />
data[ i / 8 ] <<= 1;<br />
// Now compare the low and high cycle times to see if the bit is a 0 or 1.<br />
if( high_cycles > low_cycles )<br />
{<br />
// High cycles are greater than 50us low cycle count, must be a 1.<br />
data[ i / 8 ] |= 1;<br />
}<br />
// Else high cycles are less than (or equal to, a weird case) the 50us low<br />
// cycle count so this must be a zero. Nothing needs to be changed in the<br />
// stored data.<br />
}<br />
<br />
// Check we read 40 bits and that the checksum matches.<br />
if( data[ 4 ] == ( ( data[ 0 ] + data[ 1 ] + data[ 2 ] + data[ 3 ]) & 0xFF ) )<br />
{<br />
return( true );<br />
}<br />
else<br />
{<br />
return( false );<br />
}<br />
}<br />
<br />
<br />
void DHT_nonblocking::print_raw_data()<br />
{<br />
Serial.print("Sample RAW Bits: ");<br />
<br />
for (int i = 0; i < 5; i++)<br />
{<br />
for (int bit = 7; bit >= 0; bit--)<br />
{<br />
Serial.print((data[i] >> bit) & 1);<br />
}<br />
<br />
if (i < 4)<br />
{<br />
Serial.print(" ");<br />
}<br />
}<br />
<br />
Serial.println();<br />
}<br />
</code></pre></div><script></freescript><br />
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