People who follow me, know I’m a big fan of the Elecrow CrowPi, the little suitcase with a Raspberry Pi and a lot of electronic components included. I used it already a lot in my presentations at various conferences to demonstrate #JavaOnRaspberryPi.
One of the most “fancy” electronic components is definitely a LED strip. It’s really cool to control a long strip of lights with only a few lines of code… But, there is a problem. The timing of the signals is crucial to reliably control these strips. Both Python and Java on a Raspberry Pi can struggle with these timings as they are running on Linux, a non-real-time operating system. So, for instance, pauses in the garbage collection of the Java virtual machine, or any glitch in the operating system can cause unexpected effects on the LED strips. That’s why in most projects, a microcontroller (Arduino, Raspberry Pi Pico, ESP32,…) is used to drive the LED strip. In my search for a good solution to use LED strips with Java, I stumbled on the Pixelblaze Output Expander. This small device is controlled through a serial interface, and handles the control of the LED strip. As it turns out, this is a perfect solution to offload the timing-critical operations from the Raspberry Pi and have reliable output on a LED strip.
To make it as easy as possible to get started with Java on the Raspberry Pi to interact with electronic components, I started a new section on the Pi4J website with JBang examples.
More than two years ago, I blogged about the use of the Raspberry Pi as an HDMI camera for the ATEM Mini. Although I have been using such a camera since then as my main Zoom camera, I wasn’t always happy with the image quality. The main problem was that the previous Raspberry Pi cameras had a fixed focus and it was quite hard to find the perfect focus.
Exactly one year ago, in December 2021, I published three articles of MQTT messaging with Raspberry Pi, Raspberry Pi Pico and HiveMQ Cloud. On June 30th of 2022, Raspberry Pi released a new product, that is the subject of this post: the Pico W. Yes, a new version of the original Pico, but with Wi-Fi. The new board is for sale for 6$, compared to the 4$ of the original Pico.
As I’m becoming a senior developer in terms of age, I’ve transitioned from one language to another. One of my main interests has always been clean, easy-to-understand UIs (User Interface). That journey started for me with Director (to create multimedia CD-ROMs), Flash website animation, and Flex Rich Internet Applications (= “Flash on steroids”). When I started developing with Java over 10 years ago, we had some projects with the early versions of Vaadin and JavaFX. As I went on with serverside applications, I only continued with JavaFX for some personal and side projects, and loved the way you can create a UI both with XML (FXML actually) and code, exactly the same approach I loved with Flex. Since then, my love for Java and JavaFX only grew and it’s still my major programming environment.
Looking for an affordable camera with HDMI output? Build one yourself with a Raspberry Pi Zero 2!
In the previous two posts in this series, we used Java on the Raspberry Pi mini-computer to send sensor data to HiveMQ Cloud, and visualize it on a dashboard.
A topic which comes up from time to time in questions related to Java and the Raspberry Pi, is the support of the 4th version of this board in combination with Pi4J, “the friendly object-oriented I/O API and implementation library for Java programmers to access the full I/O capabilities of the Raspberry Pi “.
Based on multiple examples from my book “Getting started with Java on Raspberry Pi”, I created a touchscreen controller for the drum booth of my son. Combined with relays boards and an Arduino this allows to control LED strips and different lights with a touch screen interface.
In my book I explain the use of bits and bytes by using a shift register SN74HC595 IC and 5101AS LED number display.
Using the Java library I created (see previous post), it was a piece of cake to create a JavaFX UI on top of it!
Next step in my book progress, is getting more into the details of hardware components. And as always starting with the smallest most-used ones: resistors!
To be able to fully document this for the book and create a demo application, I started again with creating and sharing a Java library.
The best way to understand and learn something new, is to document it yourself. That’s what I’m doing in every step for my book-in-progress. And to fully get the pinnings and headers of the different Pi-boards, I decided to gather all info into a Java library with different enums to be able to auto-generate some content for the book and use in a few different example applications.
One of the example applications in my book “Getting started with Java on the Raspberry Pi” combines a JavaFX application with Mosquitto on the Raspberry Pi to control a LED strip with an Arduino. All wireless and independent of each other as the Mosquitto-queue is dealing with exchange commands between all applications.
My very first open source JavaFX library is now available in the Maven repository! A small step for mankind, one giant leap for myself ;-)
And another summer project got finished… ;-)
My sons drum corps teacher triggered me to build an Arduino Midi controller so he could practice his rhythm skills.
Some time ago I ordered a “Breadboard Pi Bridge - Pi Ports to Breadboard in Numerical Order” and reworked my Pi test setup from the previous blogs. And it looks really good!
See https://www.pi4j.com/1.2/index.html
This project is intended to provide a friendly object-oriented I/O API and implementation libraries for Java Programmers to access the full I/O capabilities of the Raspberry Pi platform. This project abstracts the low-level native integration and interrupt monitoring to enable Java programmers to focus on implementing their application business logic.
As I was learning Spring Boot myself, I thought the easiest way to learn was trying to build an example and write about it. So here we go… :-)
While trying out what Pi4J can do, I found it could easily be extended with a JavaFX application to provide info about the headers on a Pi board. This could later be extended to a remote/local (touch) User Interface using the REST interface from this post.
As a self-study project I experimented to create a Pong game + slide shown on a Raspberry PI with Tkinter, GPIO and physical buttons.