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NanoPi M1 Plus - DHT11 control with pi4j
출처 : Java Native Interface (JNI) - Java Programming Tutorial
Use arrays (JNI) - Real's Java How-to - Rgagnon
android - How to return an array from JNI to Java? - Stack Overflow
NanoPi M1 Plus에서 pi4j로만으로 DHT11센서의 값을 읽을 수 없어 pi4j의 native 코드를 추가해서 온도 값을 가지고 오도록 수정하였습니다. 첨부한 jar을 적용해서 사용하세요.
pi4j-core.jar핀배열
| DHT11 | BCM | GPIO | Name | Pin |
| VCC | 3.3v | 1 | ||
| GND | 0v | 9 | ||
| Sensor | 3 | 22 | CTS2 | 15 |
dht11.h
int* read_dht11_dat(int pin);
dht11.c
/*
* dht11.c:
* Simple test program to test the wiringPi functions
* DHT11 test
*/
#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <dht11.h>
#define MAXTIMINGS 85
#define DHTPIN 3
int dht11_dat[5] = { 0, 0, 0, 0, 0 };
int* read_dht11_dat(int pin) {
uint8_t laststate = HIGH;
uint8_t counter = 0;
uint8_t j = 0, i;
float f; /* fahrenheit */
dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;
/* pull pin down for 18 milliseconds */
pinMode( pin, OUTPUT );
digitalWrite( pin, LOW );
delay( 18 );
/* then pull it up for 40 microseconds */
digitalWrite( pin, HIGH );
delayMicroseconds( 40 );
/* prepare to read the pin */
pinMode( pin, INPUT );
/* detect change and read data */
for ( i = 0; i < MAXTIMINGS; i++ ) {
counter = 0;
while ( digitalRead( pin ) == laststate ) {
counter++;
delayMicroseconds( 1 );
if ( counter == 255 ) {
break;
}
}
laststate = digitalRead( pin );
if ( counter == 255 )
break;
// printf("i = %d, j = %d\n", i, j);
/* ignore first 3 transitions */
if ( (i >= 4) && (i % 2 == 0) ) {
/* shove each bit into the storage bytes */
dht11_dat[j / 8] <<= 1;
if ( counter > 16 )
dht11_dat[j / 8] |= 1;
j++;
}
}
/*
* check we read 40 bits (8bit x 5 ) + verify checksum in the last byte
* print it out if data is good
*/
if ( (j >= 40) && (dht11_dat[4] == ( (dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF) ) ) {
f = dht11_dat[2] * 9. / 5. + 32;
//printf( "Humidity = %d.%d %% Temperature = %d.%d *C (%.1f *F)\n",
// dht11_dat[0], dht11_dat[1], dht11_dat[2], dht11_dat[3], f );
} else {
//printf( "Data not good, skip\n" );
}
return dht11_dat;
}
com_pi4j_wiringpi_Gpio.h 내용 추가
/* * Class: com_pi4j_wiringpi_Gpio * Method: readDHT11Data * Signature: (II)V */ JNIEXPORT jintArray JNICALL Java_com_pi4j_wiringpi_Gpio_readDHT11Data (JNIEnv *, jclass, jint);
com_pi4j_wiringpi_Gpio.c 내용 추가
#include <dht11.h>
/*
* Class: com_pi4j_wiringpi_Gpio
* Method: readDHT11Data
* Signature: (II)V
*/
JNIEXPORT jintArray JNICALL Java_com_pi4j_wiringpi_Gpio_readDHT11Data
(JNIEnv *env, jclass obj, jint pin)
{
// return (jintArray) read_dht11_dat(pin);
int size = 5;
jintArray result;
result = (*env)->NewIntArray(env, size);
if (result == NULL) {
return NULL; /* out of memory error thrown */
}
int *a1 = read_dht11_dat(pin);
int i;
// fill a temp structure to use to populate the java int array
jint fill[size];
for (i = 0; i < size; i++) {
fill[i] = a1[i]; // put whatever logic you want to populate the values here.
}
// move from the temp structure to the java structure
(*env)->SetIntArrayRegion(env, result, 0, size, fill);
return result;
}
Gpio 클래스 함수 추가
package com.pi4j.wiringpi;
public class Gpio {
public static native int[] readDHT11Data(int pin);
}
DHT11_native.java
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.NanoPiM1PlusGpioProvider;
import com.pi4j.wiringpi.Gpio;
public class DHT11_native {
private static final int MAXTIMINGS = 85;
private int[] dht11_dat = { 0, 0, 0, 0, 0 };
private final static int DHTPIN = 3; // 3;
public float getTemperature() {
float f = 0;
dht11_dat = Gpio.readDHT11Data(DHTPIN);
if ( (dht11_dat[4] == ( (dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF) ) ) {
f = (float) (dht11_dat[2] * 9. / 5. + 32);
System.out.println(String.format( "Humidity = %d.%d %% Temperature = %d.%d *C (%.1f *F)" , dht11_dat[0], dht11_dat[1], dht11_dat[2], dht11_dat[3], f) );
} else {
System.out.println( "Data not good, skip" );
}
return f;
}
private boolean checkParity() {
return (dht11_dat[4] == ((dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF));
}
public static void main (String ars[]) throws Exception {
GpioFactory.setDefaultProvider(new NanoPiM1PlusGpioProvider());
DHT11_native dht = new DHT11_native();
for (int i=0; i<10; i++) {
Thread.sleep(1000);
dht.getTemperature();
}
System.out.println("Done!!");
}
}
실행
# java -cp .:pi4j-core.jar DHT11_native Data not good, skip Humidity = 31.0 % Temperature = 23.0 *C (73.4 *F) Humidity = 30.0 % Temperature = 23.0 *C (73.4 *F) Humidity = 30.0 % Temperature = 23.0 *C (73.4 *F)
실행결과
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