Go to advanced search

by knute
Mon Jul 22, 2019 11:24 pm
Forum: Advanced users
Topic: RaspberryPi 4: heatsink or fan
Replies: 36
Views: 6855

Re: RaspberryPi 4: heatsink or fan

I saw somebody post the other day about some small fans by Noctua so I bought a 5V version. It really keeps the temp down. Now with ambient temp 27C the Pi idles at about 40C. I ran it at 98% to 99% for 20 minutes and it was about 60C at the end. I have one of those little aluminum heat sinks on the...
by knute
Mon Jul 22, 2019 10:55 pm
Forum: Beginners
Topic: Raspberry Pi 3 Temperature sensor setup
Replies: 2
Views: 21

Re: Raspberry Pi 3 Temperature sensor setup

If you have a bare sensor you need a pull-up resister. 10k will work I'm pretty sure but the device spec is for 5.1k. If you have the sensor on a board then it already has the pull-up resistor. You don't need the board you can just connect the wires. Some heat shrink tubing is good to keep them from...
by knute
Fri Jul 19, 2019 7:02 pm
Forum: Java
Topic: If else help
Replies: 12
Views: 567

Re: If else help

Use the Console class for console I/O. Simple example of what you said you wanted. import java.io.*; public class test { public static void main(String... args) { Console con = System.console(); if (con != null) { System.out.println("good console - enter a line of text"); String str = con.readLine()...
by knute
Wed Jul 17, 2019 8:34 pm
Forum: Java
Topic: JavaMail issue on Pi0 and 1 with openjdk-11
Replies: 3
Views: 115

Re: JavaMail issue on Pi0 and 1 with openjdk-11

To me it seems like JVM cannot offer appropriate ... well... Certificate? Does not support protocol? Something like that. Maybe OpenJDK11 has That's kind of what I thought but I'm not so sure now. I looked at that link but didn't see anything that I thought was obvious. I did however find a simple ...
by knute
Wed Jul 17, 2019 4:03 pm
Forum: Java
Topic: JavaMail issue on Pi0 and 1 with openjdk-11
Replies: 3
Views: 115

JavaMail issue on Pi0 and 1 with openjdk-11

I have found some sort of a problem with JavaMail and openjdk-11 on a Pi0 or 1. To run Java 11 on a Pi0 or 1 you have to include the -zero command line option since openjdk-11 java won't run on a Pi0 or 1. The fix is to install the package openjdk-11-jre-zero which will run on a Pi0 or 1. But I'm ha...
by knute
Wed Jul 17, 2019 3:53 pm
Forum: Java
Topic: java is not supported any more on Pi0 with OS buster
Replies: 6
Views: 959

Re: java is not supported any more on Pi0 with OS buster

So there is an interesting fault when openjdk-11 is installed on a Pi0 or Pi1. The script that sets the ca-certificates doesn't run because it call java without the -zero option and fails. This causes it to fail doing some things that require use of the certificate (eg. java.mail). Today I'm going ...
by knute
Wed Jul 17, 2019 2:13 pm
Forum: Java
Topic: java is not supported any more on Pi0 with OS buster
Replies: 6
Views: 959

Re: java is not supported any more on Pi0 with OS buster

So there is an interesting fault when openjdk-11 is installed on a Pi0 or Pi1. The script that sets the ca-certificates doesn't run because it call java without the -zero option and fails. This causes it to fail doing some things that require use of the certificate (eg. java.mail). Today I'm going t...
by knute
Fri Jun 28, 2019 10:22 pm
Forum: Raspbian
Topic: Suggestion: Reporting ip address in /boot/boot.ip
Replies: 37
Views: 1129

Re: Suggestion: Reporting ip address in /boot/boot.ip

I do a lot of development on a Windows 10 machine. I use it to burn my SD cards. I've installed Bonjour but for the life of me can't get it to find other computers on the network with their hostname. ... Can you find other computers by name from a Pi or other computers on the network? Newer updates...
by knute
Fri Jun 28, 2019 9:14 pm
Forum: Raspbian
Topic: Suggestion: Reporting ip address in /boot/boot.ip
Replies: 37
Views: 1129

Re: Suggestion: Reporting ip address in /boot/boot.ip

I do a lot of development on a Windows 10 machine. I use it to burn my SD cards. I've installed Bonjour but for the life of me can't get it to find other computers on the network with their hostname. What I think would be the slickest setup for people that have lots of Pis running headless using DHC...
by knute
Fri Jun 28, 2019 3:34 pm
Forum: Troubleshooting
Topic: Raspbian Buster Java8 error
Replies: 1
Views: 112

Re: Raspbian Buster Java8 error

I don't think there is any going back. What's the error?
by knute
Thu Jun 27, 2019 9:05 pm
Forum: Java
Topic: java is not supported any more on Pi0 with OS buster
Replies: 6
Views: 959

Re: java is not supported any more on Pi0 with OS buster

Buster, openjdk-11-jdk, openjdk-11-jre-zero and the -zero command line option is all that's needed. It is really slow in a Zero though.
by knute
Sun Jun 16, 2019 4:24 pm
Forum: Automation, sensing and robotics
Topic: How do I take a monitor screen and have the Pi be able to "watch it"
Replies: 1
Views: 301

Re: How do I take a monitor screen and have the Pi be able to "watch it"

I know that you can capture an image of a portion of the screen with Java. I assume that other languages have methods to do that as well.
by knute
Sat Jun 15, 2019 5:52 pm
Forum: Java
Topic: Having Trouble Stopping Audio Capture with Java
Replies: 1
Views: 350

Re: Having Trouble Stopping Audio Capture with Java

You don't say what device the TargetDataLine is connected to. If connected to a device such as a microphone, drain() will never return because the mixer connected to the microphone will continue to send data to the TargetDataLine's buffer which drain() will attempt to empty but never succeed. Just c...
by knute
Thu Jun 13, 2019 8:56 pm
Forum: Java
Topic: JavaFX application not working on Raspbian Stretch/Raspberry Pi Zero W 1.1
Replies: 8
Views: 6943

Re: JavaFX application not working on Raspbian Stretch/Raspberry Pi Zero W 1.1

ralphcorrales wrote:
Tue Jun 11, 2019 7:18 am
Have you succeeded in building OpenJFX for ARM Hard Float? Or don't you need anymore? Apparently, I lack skills to do that...
You don't have to build it, just install it:

apt install openjdk-8-jdk openjfx

and you are good to go.
by knute
Wed May 15, 2019 9:54 pm
Forum: Advanced users
Topic: Raspberry pi socket connection delay for receiving message.
Replies: 4
Views: 314

Re: Raspberry pi socket connection delay for receiving message.

I'm not sure what is causing your problem but you could send some dummy messages every so often and maybe that would keep things tuning along nicely when you need it?
by knute
Fri May 10, 2019 9:44 pm
Forum: General discussion
Topic: Execute Java code with inputs
Replies: 1
Views: 83

Re: Execute Java code with inputs

Take a look at the java.io.Console class.
by knute
Thu May 09, 2019 9:34 pm
Forum: Troubleshooting
Topic: enabling perl
Replies: 18
Views: 631

Re: enabling perl

... if you follow the instructions I gave above. Some of those instructions are unsafe. The script should not be owned by www-data, in the group www-data, or in any way writable by the account www-data. You could make the script readable and executable and not writable by the owner www-data but it ...
by knute
Thu May 09, 2019 5:11 pm
Forum: Troubleshooting
Topic: enabling perl
Replies: 18
Views: 631

Re: enabling perl

It seems that CGI in other directories is disabled by default in Apache 2.4! apache can't access files that it doesn't own or have permission to access. You can put the cgi files anywhere you want as long as apache can read and/or execute them. sudo a2enmod cgi and Options +ExecCGI Addhandler cgi-s...
by knute
Tue May 07, 2019 1:32 pm
Forum: C/C++
Topic: GCC 9.1 released
Replies: 26
Views: 3036

Re: GCC 9.1 released

Is there an uninstall script in case one doesn't like it?
by knute
Mon May 06, 2019 8:10 pm
Forum: Troubleshooting
Topic: enabling perl
Replies: 18
Views: 631

Re: enabling perl

I didn't compile it myself but I got it running with the info here: https://perl.apache.org/docs/2.0/user/i ... _fast.html

There is however an error in their configuration file and it won't work with it. That took me a while to figure out. If you want instructions let me know.
by knute
Thu May 02, 2019 7:54 pm
Forum: Other programming languages
Topic: Perl module Rpi::PIGPIO?
Replies: 0
Views: 445

Perl module Rpi::PIGPIO?

So I found this webpage: https://metacpan.org/pod/RPi::PIGPIO and wondered if there is a package for the Pi to get this Perl module or if I have to download it with CPAN?
by knute
Thu May 02, 2019 7:37 pm
Forum: Troubleshooting
Topic: enabling perl
Replies: 18
Views: 631

Re: enabling perl

DougieLawson wrote:
Thu May 02, 2019 6:23 pm
libcgi-pm-perl is an excellent module that makes writing Perl common gateway interface programs easier. It's not the stuff to get Perl running under Apache2.
Can you point me to some documentation on libcgi-pm-perl? I'm clearly not looking in the right place.

Thanks!
by knute
Thu May 02, 2019 6:20 pm
Forum: Troubleshooting
Topic: enabling perl
Replies: 18
Views: 631

Re: enabling perl

You don't need either file. sudo apt install apache2 sudo a2enmod cgid sudo systemctl restart apache2 create your perl script and put it in /usr/lib/cgi-bin set owner and group to www-data: sudo chown www-data:www-data set executable: sudo chmod 750 point your browser to: localhost/cgi-bin/test.pl i...
by knute
Thu May 02, 2019 3:35 pm
Forum: Graphics, sound and multimedia
Topic: Low level sound API documentation
Replies: 3
Views: 348

Re: Low level sound API documentation

I wrote a simple point to point intercom for the Pi and Windows using JavaSound. It is simple to program and has the advantage of running the same code on both systems. You can see the code here: pi.knutejohnson.com.

Go to advanced search