Recent wiringpi/JNI build

[Gus189]

Hello,
Wondering if anyone had a fairly recent example of setting up wiringPi/JNI in Android Studio...

Been hacking away at some examples I found here but they won't build in recent Android Studio with Android 8+...

I'm not a super expert on JNI stuff and was wondering if anyone had any recent examples or howTos.

I'm running Android 9 on the C4, sdk 27+

Thanks,
Gus

[joerg]

Are you using Java or Kotlin?
I can set up an example and guide you through the first steps.

[Gus189]

Java. Thanks!

[joerg]

OK. So I recommend to first clone the wiringPi from github and compile it:

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git clone https://github.com/hardkernel/wiringPi.git
cd wiringPi

The to make it compile with the NDK add a jni folder and add a Application.mk and a Android.mk there.
wiringPi/jni/Android.mk

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LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_C_INCLUDES += \
    $(LOCAL_PATH)/../wiringPi

LOCAL_MODULE    := wiringPi
LOCAL_SRC_FILES := \
        ../wiringPi/ads1115.c        \
        ../wiringPi/mcp23008.c        \
        ../wiringPi/mcp4802.c        \
        ../wiringPi/piHiPri.c        \
        ../wiringPi/sr595.c        \
        ../wiringPi/bmp180.c        \
        ../wiringPi/mcp23016.c        \
        ../wiringPi/odroidc1.c        \
        ../wiringPi/odroidn2.c        \
        ../wiringPi/piThread.c        \
        ../wiringPi/wiringPi.c        \
        ../wiringPi/mcp23017.c        \
        ../wiringPi/odroidc2.c        \
        ../wiringPi/odroidc4.c        \
        ../wiringPi/odroidhc4.c        \
        ../wiringPi/drcSerial.c        \
        ../wiringPi/mcp23s08.c        \
        ../wiringPi/odroidn1.c        \
        ../wiringPi/wiringPiI2C.c        \
        ../wiringPi/ds18b20.c        \
        ../wiringPi/mcp23s17.c        \
        ../wiringPi/sn3218.c        \
        ../wiringPi/wiringPiSPI.c        \
        ../wiringPi/htu21d.c        \
        ../wiringPi/mcp3002.c        \
        ../wiringPi/odroidxu3.c        \
        ../wiringPi/softPwm.c        \
        ../wiringPi/wiringSerial.c        \
        ../wiringPi/max31855.c        \
        ../wiringPi/mcp3004.c        \
        ../wiringPi/pcf8574.c        \
        ../wiringPi/softServo.c        \
        ../wiringPi/wiringShift.c        \
        ../wiringPi/max5322.c        \
        ../wiringPi/mcp3422.c        \
        ../wiringPi/pcf8591.c        \
        ../wiringPi/softTone.c



LOCAL_CFLAGS    += -UNDEBUG -DANDROID -Wno-return-type

LOCAL_LDLIBS    := -ldl -llog
include $(BUILD_SHARED_LIBRARY)


include $(CLEAR_VARS)
LOCAL_C_INCLUDES += \
    $(LOCAL_PATH)/../wiringPi

LOCAL_MODULE    := wiringPiDev
LOCAL_SRC_FILES := \
    ../devLib/ds1302.c     \
    ../devLib/maxdetect.c  \
    ../devLib/piNes.c      \
    ../devLib/gertboard.c  \
    ../devLib/lcd128x64.c  \
    ../devLib/lcd.c        \
    ../devLib/piGlow.c     \
    ../devLib/scrollPhat.c \
    ../devLib/piFace.c 

LOCAL_SHARED_LIBRARIES := libwiringPi

LOCAL_LDLIBS    := -ldl -llog

LOCAL_CFLAGS    += -DEBUG -DANDROID  -Wno-return-type
include $(BUILD_SHARED_LIBRARY)


include $(CLEAR_VARS)

LOCAL_MODULE    := gpio
LOCAL_SRC_FILES := ../gpio/gpio.c ../gpio/readall.c
LOCAL_C_INCLUDES +=   $(LOCAL_PATH)/../wiringPi $(LOCAL_PATH)/../devLib/

LOCAL_CFLAGS    += -DEBUG -DANDROID -Wno-return-type
LOCAL_LDLIBS := -llog
LOCAL_SHARED_LIBRARIES := libwiringPi libwiringPiDev

include $(BUILD_EXECUTABLE)

wiringPi/jni/Application.mk

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NDK_TOOLCHAIN_VERSION=clang
APP_ABI :=  armeabi-v7a arm64-v8a
APP_PLATFORM := android-21

It's old style, but it works.
Compile it:

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/path/to/Android/Sdk/ndk-bundle/ndk-build -B
...
[arm64-v8a] Install        : gpio => libs/arm64-v8a/gpio
[arm64-v8a] Install        : libwiringPi.so => libs/arm64-v8a/libwiringPi.so
[arm64-v8a] Install        : libwiringPiDev.so => libs/arm64-v8a/libwiringPiDev.

Do it, meanwhile I will write nexte steps...

[Gus189]

Cool, I'll try to get started tonight.

Thanks,
Paul

[joerg]

Then create a new project in AndroidStudio.
You need to add a folder cpp under src/main. Then add file CmakeLists.txt with right mouse click on it: New - File and a file wpi_android.cpp with New - C/C++ Source File.
src/main/cpp/CmakeLists.txt

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cmake_minimum_required(VERSION 3.4.1)
find_library( log-lib log )

//set path to the parent folder of wiringPi:
set(distribution_DIR /home/joerg/Development/Ndk)

add_library( wiring SHARED IMPORTED )
set_target_properties( wiring PROPERTIES IMPORTED_LOCATION
        ${distribution_DIR}/wiringPi/libs/${ANDROID_ABI}/libwiringPi.so )

add_library( wpi_android  SHARED  wpi_android.cpp )

target_include_directories( wpi_android PUBLIC /home/joerg/Development/Ndk/wiringPi/wiringPi )

target_link_libraries( wpi_android ${log-lib} wiring )

The wpi_android is a library that interfaces the wiringPi with Java.
src/main/cpp/wpi_android.cpp

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//
// Created by joerg on 18.02.21.
//

#include <jni.h>
#include <android/log.h>
#include <stdio.h>
#include <string.h>

#define LOGI(...)  __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define LOG_TAG "wpi_android"

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/system_properties.h>

#include <softPwm.h>
#include <dlfcn.h>
#include "wiringPi.h"

#ifdef __cplusplus
extern "C" {
#endif

#define I2C_DEVICE  "/dev/i2c-1"


jint Java_com_jw_wiringpi_wpiAndroid_wiringPiSetupSys(JNIEnv* env, jobject obj) {
    LOGI("Entering wiringPiSetup");
    return wiringPiSetupSys();
}


jint Java_com_jw_wiringpi_wpiAndroid_wiringPiSetup(JNIEnv* env, jobject obj) {
    return wiringPiSetup();
}

//void pullUpDnControl (int pin, int pud)
void Java_com_jw_wiringpi_wpiAndroid_pullUpDnControl(JNIEnv* env, jobject obj, jint port, jint pud) {
    return pullUpDnControl(port, pud);
}

//void pinMode (int pin, int mode)
void Java_com_jw_wiringpi_wpiAndroid_pinMode(JNIEnv* env, jobject obj, jint port, jint mode) {
    return pinMode(port, mode);
}

//void pinModeAlt (int pin, int mode)
void Java_com_jw_wiringpi_wpiAndroid_pinModeAlt(JNIEnv* env, jobject obj, jint port, jint mode) {
    pinModeAlt(port, mode);
}

jint Java_com_jw_wiringpi_wpiAndroid_digitalRead(JNIEnv* env, jobject obj, jint port) {
    return digitalRead(port);
}

//int getAlt (int pin)
jint Java_com_jw_wiringpi_wpiAndroid_getAlt(JNIEnv* env, jobject obj, jint port) {
    return getAlt(port);
}

void Java_com_jw_wiringpi_wpiAndroid_digitalWrite(JNIEnv* env, jobject obj, jint port, jint onoff) {
    digitalWrite(port, onoff);
}

jint Java_com_jw_wiringpi_wpiAndroid_analogRead(JNIEnv* env, jobject obj, jint port) {
    return analogRead(port);
}

jint Java_com_jw_wiringpi_wpiAndroid_softPwmCreate(JNIEnv* env, jobject obj, jint port, jint value, jint range) {
    return softPwmCreate(port, value, range);
}

void Java_com_jw_wiringpi_wpiAndroid_softPwmWrite(JNIEnv* env, jobject obj, jint port, jint value) {
    softPwmWrite(port, value);
}

void Java_com_jw_wiringpi_wpiAndroid_softPwmStop(JNIEnv* env, jobject obj, jint port) {
    softPwmStop(port);
}

void Interrupt(void) {
    LOGI("Interrupt");
}

jint Java_com_jw_wiringpi_wpiAndroid_wiringPiISR(JNIEnv* env, jobject obj, jint port, jint edge) {
    return wiringPiISR (port, edge, &Interrupt);
}


#ifdef __cplusplus
}
#endif

Note this syntax: Java_com_jw_wiringpi_wpiAndroid. You can change to your own com_jw, but I recommend to stay with wiringpi_wpiAndroid.
Therefore it's needed to add a package to your folder src/main/java: xxx.xx.wiringPi and there a Java class wpiAndroid.
wpiAndroid.java

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package com.jw.wiringpi;

public final class wpiAndroid {
    static {
        System.loadLibrary("wpi_android");
    }
    static public native int wiringPiSetup();
    static public native int wiringPiSetupSys();
    static public native void digitalWrite(int port, int onoff);
    static public native int digitalRead(int port);
    static public native void pullUpDnControl(int port, int pud);
    static public native void pinMode(int port, int mode);
    static public native void pinModeAlt(int port, int mode);
    static public native int getAlt(int port);
    static public native int softPwmCreate(int port, int value, int range);
    static public native void softPwmWrite  (int port, int value) ;
    static public native void softPwmStop   (int port) ;
}

You see the syntax is needed as path to the function.

Now it's missing some entry in app/build.gradle, to make AndroidStudio compile it.

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    defaultConfig {
        ...
        ndk {
            ldLibs "log"
            abiFilters 'armeabi-v7a', 'arm64-v8a'
        }
    }
    
    externalNativeBuild {
        // Encapsulates your CMake build configurations.
        cmake {

            // Provides a relative path to your CMake build script.
            path "src/main/cpp/CMakeLists.txt"
        }
    }

Now you should be able to use the functions in wpiAndroid with your Java code.

[Gus189]

Thanks again for this!

I'm getting a duplicate symbol error building it...

$ ....AppData/Local/Android/sdk/ndk-bundle/ndk-build.cmd -B
[armeabi-v7a] Compile thumb : gpio <= gpio.c
[armeabi-v7a] Compile thumb : gpio <= readall.c
[armeabi-v7a] Compile thumb : wiringPi <= ads1115.c
[armeabi-v7a] Compile thumb : wiringPi <= mcp23008.c
[armeabi-v7a] Compile thumb : wiringPi <= mcp4802.c
...

[armeabi-v7a] Compile thumb : wiringPi <= pcf8591.c
[armeabi-v7a] Compile thumb : wiringPi <= softTone.c
[armeabi-v7a] SharedLibrary : libwiringPi.so
ld: error: duplicate symbol: phyToGpio
>>> defined at odroidn2.c:165 (C:/WiringPIBuild/wiringPi/jni/../wiringPi\odroidn2.c:165)
>>> C:/WiringPIBuild/wiringPi/obj/local/armeabi-v7a/objs/wiringPi/__/wiringPi/odroidn2.o:(phyToGpio)
>>> defined at odroidc2.c:142 (C:/WiringPIBuild/wiringPi/jni/../wiringPi\odroidc2.c:142)
>>> C:/WiringPIBuild/wiringPi/obj/local/armeabi-v7a/objs/wiringPi/__/wiringPi/odroidc2.o:(.bss.phyToGpio+0x0)

ld: error: duplicate symbol: pinToGpio
>>> defined at odroidn2.c:165 (C:/WiringPIBuild/wiringPi/jni/../wiringPi\odroidn2.c:165)
>>> C:/WiringPIBuild/wiringPi/obj/local/armeabi-v7a/objs/wiringPi/__/wiringPi/odroidn2.o:(pinToGpio)
>>> defined at odroidc2.c:142 (C:/WiringPIBuild/wiringPi/jni/../wiringPi\odroidc2.c:142)
>>> C:/WiringPIBuild/wiringPi/obj/local/armeabi-v7a/objs/wiringPi/__/wiringPi/odroidc2.o:(.bss.pinToGpio+0x0)
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

[joerg]

On what system you are compiling? >>> C:/WiringPIBuild/... looks like Windows?
I have compiled it on my Linux system without error.
What happens if you change NDK_TOOLCHAIN_VERSION to gcc in Application.mk?

[Gus189]

Yep, Windows. Still fails same way with gcc but, I can try to set this up on a Linux system....

[Gus189]

It built ok on Linux. Do I need to run Android Studio on Linux as well or can I copy the wiringpi I built on linux to my Windows Android Studio? Sorry for the dumb questions....

[joerg]

It might work this way. But I don‘t have any experience with AndrodStudio on Windows.

[Gus189]

I'll try to make it work, but if not, I'll just use Linux. Thanks for the help and I'll let you know how it goes.


Gus