Could gpioCfgClock be made available

[pietdewinter]

[hagego]

see also #174

[savageautomate]

It looks like the Pi4J PIGPIO library does expose the gpioCfgClock function directly in the JNI native library. So in theory you should be able to access this function via Java.

pi4j-v2/libraries/pi4j-library-pigpio/src/main/java/com/pi4j/library/pigpio/internal/PIGPIO.java

Line 1272 in 9763aa3

public static native int gpioCfgClock(int cfgMicros, int cfgPeripheral, int cfgSource);

However, it's not exposed via the higher level Pi4J framework or APIs. So you would need to reference the JNI library directly in your code to execute this function.

[hagego]

I have tried it, but get a crash so far. According to pigpio documentation, this function must be called before gpioInitialise(), so to keep it simple for a first experiment I hacked PgioNativeImpl.gpioInitialise()

pi4j-v2/libraries/pi4j-library-pigpio/src/main/java/com/pi4j/library/pigpio/impl/PiGpioNativeImpl.java

Line 84 in dfbaa0f

public int gpioInitialise() {

like this:

    if(!this.initialized) {
        // disable socket and pipes interfaces
        int rslt = PIGPIO.gpioCfgInterfaces(3);
        
        PIGPIO.gpioCfgClock(5,0,0);            

        // initialize the PiGpio native library
        result = PIGPIO.gpioInitialise();
        validateResult(result);
        
        // initialization successful
        this.initialized = true;
        logger.debug("[INITIALIZE] -- INITIALIZED SUCCESSFULLY");
    }

But get a crash:

2022-01-30 10:30:18 FINEST com.pi4j.library.pigpio.impl.PiGpioNativeImpl [INITIALIZE] -> STARTED
2022-01-30 10:30:18 FINE com.pi4j.library.pigpio.util.NativeLibraryLoader Attempting to load library [libpi4j-pigpio.so] using path: [/lib/armhf/libpi4j-pigpio.so]
2022-01-30 10:30:19 FINE com.pi4j.library.pigpio.util.NativeLibraryLoader Library [libpi4j-pigpio.so] loaded successfully using embedded resource file: [/lib/armhf/libpi4j-pigpio.so]
2022-01-30 10:30:19 SEVERE alarmpi.AlarmPi Uncaught runtime exception in main thread: 'int com.pi4j.library.pigpio.internal.PIGPIO.gpioCfgClock(int, int, int)'
2022-01-30 10:30:19 SEVERE alarmpi.AlarmPi Uncaught runtime exception in main thread: null
2022-01-30 10:30:19 SEVERE alarmpi.AlarmPi com.pi4j.library.pigpio.internal.PIGPIO.gpioCfgClock(Native Method)
2022-01-30 10:30:19 SEVERE alarmpi.AlarmPi com.pi4j.library.pigpio.impl.PiGpioNativeImpl.gpioInitialise(PiGpioNativeImpl.java:93)
2022-01-30 10:30:19 SEVERE alarmpi.AlarmPi com.pi4j.library.pigpio.PiGpio.initialise(PiGpio.java:174)

Is there anything else that needs to be done before a JNI function can be used ? Sorry, no expert in JNI...

[hagego]

I digged further and found that this function is commented out in the wrapper header:

pi4j-v2/libraries/pi4j-library-pigpio/src/main/native/com_pi4j_library_pigpio_internal_PIGPIO.h

Line 898 in dfbaa0f

//JNIEXPORT jint JNICALL Java_com_pi4j_library_pigpio_internal_PIGPIO_gpioCfgClock

And does not exist in the .c file. I tried to fix/hack also this part, but had to give up for now as I ran into too many issues I could not solve with my limited understanding of the structure of the project

[hagego]

As soon as I compile the native code (using release 2.1.1 sources w/o any changes) using -Pnative in mvn, the JVM crashes when loading libpi4j-pigpio.so from the resulting jar. I guess cross-compiling the native code should work, or are there any known issues ? So something wrong with my setup, for the moment I got stuck

[hagego]

I found out that the crash happened because I was using an arm6 Pi which is not supported by the toolchain. Using the docker based toolchain things are now working.
I can confirm that my sound output is working fine again when calling gpioCfgClock(5,0,0) gefore Initialise().
The change is simple, requires around 10 lines of code, I hope this can be made part of the master branch

[FDelporte]

@hagego that is really great news and thanks a lot for taking the time to fully research this topic!!!
would you be willing to provide a pull request with this change?

[hagego]

willing - sure ;-)
I am no git expert but I should manage. But I expect someone has to grant me permissions to do so ?

[FDelporte]

two possible solutions:

1. Quick - not good: you send me the changes and I create a pull request, but that would make me the contributor ;-)
2. Not quick - very good: go to the top of this page, push the fork button which makes a copy of this project in your account, modify there, and from your repository create a pull request back to the Pi4J project.

Or try 2. and if it fails, switch to 1. :-)

[hagego]

Done. At least I tried to do so ;-)
PiGpio interface got a new method gpioCfgClock()

[FDelporte]

This is now in release 2.2.0, see https://pi4j.com/about/release-notes/