129 lines
4.8 KiB
Markdown
129 lines
4.8 KiB
Markdown
# mpdlistenpy
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This python script is supposed to run on a rpi and does the following :
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* Relay trigger : Watches a MPD instance for play/pause/stop states and activates a relay via GPIOs accordingly ; the usecase for this is powering on/off a pair of speakers only when something is running.
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* OLED display : Drives a 0.96" OLED display (ssd1306) to display MPD status (volume, current artist, album, title...)
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* Button input : watches GPIOs for button input ; I'm using 5 push buttons for controlling playback (previous, next, toggle playback, stop, menu) or browse the database and add stuff to the playlist.
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* Potentiometer input : Watches a GPIO for estimating the resistance of a rotary potentiometer and set volume accordingly.
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## Setup
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### Software
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1. Install the latest **light** version of Raspberry Pi OS and run it on the RPI model of your choice.
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2. Install the following dependencies
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### Hardware
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#### Overall GPIOs usage
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| FUNCTION | GPIO # |
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| --- | --- |
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| OLED | GND, 3.3V, 2(SDA), 3(SCL) |
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| 5 BUTTONS | GND, 7, 8, 9, 11, 25 |
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| POTENTIOMETER | GND, 3.3V, 23 |
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| RELAY | GND, 5V, 17 |
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You can check these here : [https://pinout.xyz/](https://pinout.xyz/)
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#### Oled screen
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Using the SSD1306 OLED screen involves a few steps described here :
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[https://luma-oled.readthedocs.io/en/latest/hardware.html](https://luma-oled.readthedocs.io/en/latest/hardware.html)
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and here :
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[https://luma-oled.readthedocs.io/en/latest/software.html](https://luma-oled.readthedocs.io/en/latest/software.html)
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Once you've gone through these steps, you should be good to go.
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#### Relay circuit
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We're using the circuit described on projects-raspberry.com :
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##### Components
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* 5V DC coil relay
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* BC337 NPN transistor
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* 1N4002 [diode](https://en.wikipedia.org/wiki/1N400x_general-purpose_diodes)
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* 1KΩ resistor
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##### Diagram
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*source: [https://projects-raspberry.com/raspberry-pi-driving-a-relay-using-gpio/](https://web.archive.org/web/20240217011938/https://projects-raspberry.com/raspberry-pi-driving-a-relay-using-gpio/)*
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#### Buttons circuit
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Dead simple way described here, using a common GND, and 1 GPIO/button :
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[http://razzpisampler.oreilly.com/ch07.html](https://web.archive.org/web/20240121074741/http://razzpisampler.oreilly.com/ch07.html)
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The only difference is the addition of a resistor on the GND rail.
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If you're short on GPIOs, there is a way to use a single GPIO for multiple buttons based on resistance described here :
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[https://www.instructables.com/RaspberryPi-Multiple-Buttons-On-One-Digital-Pin/](https://www.instructables.com/RaspberryPi-Multiple-Buttons-On-One-Digital-Pin/)
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#### Potentiometer circuit
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Using the 'step response' method described [here](http://razzpisampler.oreilly.com/ch08.html#Discussion) (It's the same principle as in the link above),
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we can use an analog potentiometer to control volume.
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The solution described in the previous link is not very accurate though, so we'll be using an alternative solution offered by abyz.me.uk :
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[https://abyz.me.uk/rpi/pigpio/examples.html#Python_pot_cap_py](https://abyz.me.uk/rpi/pigpio/examples.html#Python_pot_cap_py)
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##### Components
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* 100nf Ceramic capacitor
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* 5KΩ Potentiometer
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##### Diagram
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```
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3V3 ----- Potentiometer --+-- Capacitor ----- Ground
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+-- GPIO 23
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```
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Instructions for use are in the source file. The library ('pot_cap.py') is included in this project for convenience.
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You might have to install the 'pigpio' library though :
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```
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sudo apt install python3-pigpio
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```
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You can find out more about installing 'pigpio' here :
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[https://abyz.me.uk/rpi/pigpio/download.html](https://abyz.me.uk/rpi/pigpio/download.html)
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## Optional steps
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### Installing the systemd service
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* Copy the provided service file 'mpdlistenpy.service' to '~/.config/systemd/user/mpdlistenpy.service'.
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* Update, enable and start the service as a user :
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```
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# If you need to edit the path to the script (should be in ~/mpdlisten by default)
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# systemctl --user --full edit mpdlistenpy.service
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systemctl --user daemon-reload
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systemctl --user enable mpdlistenpy.service
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systemctl --user start mpdlistenpy.service
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```
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### Automounting Samba shares on startup
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[](gist)
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*source :* [https://root.nix.dk/en/utility-scripts/mount-samba-share-as-user](https://root.nix.dk/en/utility-scripts/mount-samba-share-as-user)
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### Automounting USB
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[https://gist.github.com/zebrajaeger/168341df88abb6caaea5a029a2117925](https://gist.github.com/zebrajaeger/168341df88abb6caaea5a029a2117925)
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