Author: Phil Birch

Posted on

Reskinning Max2play

Reskinning Max2play

Max2play is a great way to have an out of the box music server running on a Raspberry Pi with a touch screen. I’ve installed Max2play on a Raspberry Pi 3 and 7 inch touch screen. The only problem with it is that I would like to run other software on the Pi as well (such as control my Phillips Hue lighting). Out the box, the Pi now boots up and runs the full screen Jivelite app which controls the music.  There are two options I could think of: 1. Write a plugin for Jivelite to control the Hue lights, or 2, control the lighting with a separate app and have the ability to launch jivelite manually. I went for 2 since Jivelite is written in Lua which I don’t know.

The first problem is how to launch Jivelite manually. For this I added a Jivelite icon to the desktop.  I’m assuming Max2play is installed with Jivelite options and everything is working.

In the Jivelite plugin settings, disable autostart. In the Settings/Reboot tab, enable Autostart desktop (the desktop is normally started with the jivelite plugin so we need to enable it here).

In the Pi’s file manager go to Edit/Preferences – enable ‘Open files with Single click’ – it’s not easy double clicking with the touch screen. You might also want to increase the icon sizes whilst your there. These setting affect the desktop as well.

SSH into the Raspberry pi – either from the terminal or via the web plugin you can install. Go to the desktop folder and create a desktop launch shortcut. We will start by making one to launch jivelite. So create a text file with nano jivelite.desktop and add

[Desktop Entry]

Type=Application

Icon=/home/pi/music.png  <edit this to point to your own icon>

Name=Jivelite

Comment=Start the Jivelite music player

Exec=/opt/jivelite/jivelite/bin/jivelite

Save the file and that’s it. You should be now be able to launch jivelite from the desktop icon. The quit button does not quit the application (it seems to stop the music), so you have to quit from the menu options on Jivelite. (There appears to be a patch file that creates this behavior but I’ll investigate that at a latter date.)

To autostart at login, make a symbolic link to the .desktop file and place it in ~/.config/autostart

You may want to disable the screensaver which blanks the screen after 10 minutes as is. Remove the @xscreensaver -no-splash line from /etc/xdg/lxsession/LXDE/autostart and from ~/.config/lxsession/LXDE/autostart Stopping the screensaver server has no effect. I’m not sure what causes the screen to blank when running the GUI. It might be power saving in X. To disable the screensaver, the easiest method is to install a screensaver client and configure that not to run.

sudo apt-get install xscreensaver

After that’s completed there will be a screensaver option in the LXDE GUI menu. Run that and disable the screensaver from there.

 

Posted on

Connecting an LED to a single board computer

Just a few notes on powering LEDs from single board computers. I’ve just started playing with an Adafruit Feather Huzzah which has just turned up with with a starting kit containing LEDs, switches, resistors and interestingly no wires – but I suppose I’ve got plenty of those around.

The Huzzah powered by an ESP8266 which is actually a wi-fi chip with a full TCP/IP stack and integrate mirco-controller that can be programmed via PlatformIO or the Arduino IDE. It’s only 80MHz but has 4Mb of flash, 9 GPIO pins and a single 1V max ADC. The chip is 3.3V and max current per GPIO is only 12mA.

Many of the GPIO are dual purposed. #0, #2, #15 and #16 are used for boot-mode detection and boot loading. I would avoid these unless really needed.

That leaves #4,#5,#12,#13.

In the starter kit there is a red LED (1.85-2.5V forward voltage, at 20mV current). The longer of the wires is the anode (+ve).

LEDs are current controlled devices so if you just wire them to voltage source (as in a GPIO pin) they will draw as much current as they can and either your LED or your source will go bang. We need to put a current limiting resistor in place and its value is given by

\( R=\frac{V_s-V_f}{I_{max}} \)

So worse case forward voltage is 1.85V and the max current is 12mA. This requires a resistor of 121 Ohms. So anything larger than this should be ok, the larger it is the dimmer the LED will be.