Set sample rate from pi4j API #294
Replies: 5 comments 6 replies
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When I run your code I see PIGPIO ERROR: PI_HPWM_ILLEGAL; illegal: return PWM in use for main clock But I believe for the same reason as you observed your error, Initialize attempted twice. Maybe you already debugged this to see that Pi4J.newAutoContext(); results in all/any providers being created thus calling initialize on the Pigpio provider. Your creating a Pigpio provider instance prior to this broke the normal steps. Answer, I do not see a means to accomplish this without modification of the Pi4j code base, and I am not suggesting that be done. I will list two of the Pi4j leads to allow their input/suggestions. @eitch @FDelporte |
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hi, good remark @taartspi about the newAutoContext. So we are discussing that problem separately :-) @msawicki-poland without testing the code myself, so there could still be errors, I would like to propose the following structure. Maybe also try-catches to be added for easier debugging? |
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Exception in thread "main" java.lang.NullPointerException: Cannot invoke "com.pi4j.io.pwm.Pwm.on(java.lang.Number, int)" because "TestPwm.pwm" is null at TestPwm.main(TestPwm.java:17) |
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For the null exception var pi4j = Pi4J.newAutoContext(); remove var, so the class' pi4j variable is set. Then you will hit the next problem exception PWM clock in use. To fix this pigpio.gpioCfgClock(2, 1, 0); // leave clock using the PCM set the second parm to 1, then the PCM remains the clock (it was the default clock prior to this method call) I can see the LED very dimly on, from reading specs and posts I am not certain what is the actual max frequency you may obtain. |
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and I got: |
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It will be a couple days before i have time to setup my environment. Your error is sensible as you called initialize but i dont know what is different in my workspace that i go past this and see the clock assignment error. Maybe i can figure what is the difference |
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Also question is if calling pi4j = Pi4J.newAutoContext(); and then pwm.on(50,1); will use new sample rate set in initPiGpio method. |
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last question first. Using the debugger I see the reference number for the pigpio created by PiGpio.newNativeInstance is the same reference number used in the pwm.on() methods, so I believe you are using the same instance. Pi4 : Using pi4j snapshot 2.3.0, I can build and run on either java 11 or 17 with no errors. I do not know what is different on our environments. I suggest adding more try/catch and use the debugger or getMessage on the exception to narrow down our differences. |
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Did you resolve this ? If not I would be interested to see added try/catches to print the stacktrace. I am curious what is different that this simple program behaves differently your machine versus mine. |
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I got something like this With this code: import com.pi4j.Pi4J;
import com.pi4j.context.Context;
import com.pi4j.io.pwm.Pwm;
import com.pi4j.io.pwm.PwmType;
import com.pi4j.library.pigpio.PiGpio;
public class TestPwm {
private static Pwm pwm = null;
private static Context pi4j;
public static void main(String[] args) throws Exception {
pi4j = Pi4J.newAutoContext();
initPiGpio();
initGPIOCM4();
pwm.on(50, 1);
while (true) {
// Timeout here?
}
}
private static void initPiGpio() {
try {
var pigpio = PiGpio.newNativeInstance();
pigpio.gpioCfgClock(2, 1, 0);
pigpio.initialize();
} catch (Exception e) {
System.out.println("Error in initPiGpio " + e.getMessage());
e.printStackTrace();
}
}
private static void initGPIOCM4() {
var configPwm = Pwm.newConfigBuilder(pi4j)
.address(13)
.pwmType(PwmType.HARDWARE)
.provider("pigpio-pwm")
.initial(0)
.shutdown(0)
.build();
try {
pwm = pi4j.create(configPwm);
} catch (Exception e) {
System.out.println("Error in initGPIOCM4 " + e.getMessage());
e.printStackTrace();
}
}
} |
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You made a major change between discussion #293 and this entry #294. You changed from pwm software to hardware timing. #2 In this discussion code, the example code you supplied does not require the method initPiGpio. The function gpioCfgClock pertain to only software PWM. |
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Hi,
I implemented simple app like this:
and when I run it I got error PI_INITIALISED; function called after gpioInitialise.
How to fix it so I can set sample rate from Java?
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