Reliable rotary encoder (100%) using dtoverlay and python-evdev?

RebornLoophole · December 27, 2019 at 10:21 AM

I am trying to find a solution for a 100% reliable rotary encoder interface to control KODI running under LibreElec. My code (see below add-on.py code) is run as a simple add-on.

As the interface for my switches I used GPIO and later changed this to GPIOZERO in which I read the state of a select button and rotary encoder to navigate through the menu. The rotary encoder code sometimes gives a wrong direction (UP or DOWN) and the button sometimes gives a double SELECT. I have debounced all keys with external R-C filters and checked with my oscilloscope the quality of the signal which is stable. It seems to me that the overall timing and interrupt latency cannot be guaranteed maybe because of some higher (interrupt or process) priorities. I was looking into a alternative solution by using a rotary-encoder dtoverlay, which seems to be available as a standard part of LibreElec, but I do not have any experience on this yet. Examples on the Internet use dtoverlay in combination with python-evdev, but I am not sure if this is supported by LibreElec. Is there anyone who has experience with this on LibreElec?

As yet I do not believe I will find a good solution under LibreElec with my limited system and software knowledge. But I want to solve this problem and so I will also continue exploring external hardware implementations, in which the rotation direction is determined by means of a schmitt trigger and D-flip flop to identify the rotation direction; thereby making it less dependant on SW response and SW timing.

However should anyone of you have good experiences with a 100% reliable rotary encoder implementation in SW under LibreElec, then I look forward to your recommendations.

#!/usr/bin/python

#coding: utf8

import sys

import xbmcaddon

import xbmcgui

sys.path.append('/storage/.kodi/addons/virtual.rpi-tools/lib')

from gpiozero import LED

from gpiozero import Button

from signal import pause

from time import sleep

addon = xbmcaddon.Addon()

addonname = addon.getAddonInfo('name')

blue = LED(27)

btn = Button(17)

pin_a = Button(23,pull_up=True) # Rotary encoder pin A connected to GPIO23

pin_b = Button(24,pull_up=True) # Rotary encoder pin B connected to GPIO24

def pin_a_rising(): # Pin A event handler

if pin_b.is_pressed:

xbmc.executebuiltin('Action(Up)')

def pin_b_rising(): # Pin B event handler

if pin_a.is_pressed:

xbmc.executebuiltin('Action(Down)')

Button.was_held = False

Button.hold_time = 0.5

def held(btn):

Button.was_held = True

xbmc.executebuiltin('Action(ParentDir)') # Select was held for a long time

def released(btn):

if not Button.was_held:

pressed()

Button.was_held = False

def pressed():

xbmc.executebuiltin('Action(Select)') # Select was pressed shortly

while True:

btn.when_held = held

btn.when_released = released

pin_a.when_pressed = pin_a_rising # Register the event handler for pin A

pin_b.when_pressed = pin_b_rising # Register the event handler for pin B

meinnamehier · June 3, 2020 at 2:27 PM

Hi,

just saw this. I do not have a 100% reliable solution, but maybe some enhancements:

1) You can use "bounce_time" on our btn, which will do software debouncing.

2) I tried around with that topic for some time and ended up using a queue in which the events are written to and read again.

Check out my code below, I am trying to do basically the same stuff (with added horiztontal scrolling). Also take a look at the while loop - the way it is done it will close down properly and not hang on shutdown or so.

Code

#!/usr/bin/env python

# In Libreelec, gpiozero is located as below, must be in path
import sys
sys.path.append('/storage/.kodi/addons/virtual.rpi-tools/lib')


# Import libraries
import xbmc
import Queue

# Try to import gpiozero

import gpiozero as gpz


#Create Queue
q = Queue.Queue()
#Monitor for checking for aborts
monitor = xbmc.Monitor()
#No buttons were held at start
gpz.Button.was_held = False

def rotary_dt_rising():                    # rotary A event handler
    if rotary_button.is_pressed:
        if rotary_clk.is_active:             # rotary A rising while A is active is a clockwise turn
            q.put('Action(Right)')
    else:
        if rotary_clk.is_active:
            q.put('Action(Down)')  

def rotary_clk_rising():                    # rotary B event handler
    if rotary_button.is_pressed:
        if rotary_dt.is_active: 
            q.put('Action(Left)')
    else:
        if rotary_dt.is_active:
            q.put('Action(Up)')     # rotary B rising while A is active is a clockwise turn

def rotary_button_held(rotary_button):
    rotary_button.was_held = True

def rotary_button_release(rotary_button):
    if not rotary_button.was_held:
        q.put('Action(Select)')
    rotary_button.was_held = False
    
def close_the_buttons(): # need to be closed so KODI can exit
    rotary_dt.close()          
    rotary_clk.close()         
    rotary_button.close()     

#Create elements for rotary switch
rotary_dt = gpz.DigitalInputDevice(27)          # Rotary encoder rotary A connected to GPIO27
rotary_clk = gpz.DigitalInputDevice(22)         # Rotary encoder rotary B connected to GPIO17
rotary_button = gpz.Button(17, bounce_time=0.01, hold_time=0.5)     # Rotary button connected to GPIO22  

#Display Start Notification
#xbmc.executebuiltin('Notification(Boombox Skript gestartet, abortRequested FALSE, 1000)')

while not monitor.abortRequested():
    #Rotary
    rotary_dt.when_activated = rotary_dt_rising      # Register the event handler for rotary A
    rotary_clk.when_activated = rotary_clk_rising      # Register the event handler for rotary B
    rotary_button.when_held = rotary_button_held
    rotary_button.when_released = rotary_button_release

    # Start queue loop
    while not q.empty():
        message = q.get()
        xbmc.executebuiltin(message)
    if monitor.waitForAbort(0.1):
        break

close_the_buttons()
sys.exit()

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adarmalik · October 4, 2020 at 6:02 PM

Just in case someone is interested: I have build a solution utilizing dtoverlay and manual reading of the input device.

GitHub - adarmalik/service.rotdev: Kodi add-on to make a KY040 rotary encoder work as volume control

tobor · March 8, 2022 at 3:03 PM

adarmalik,

I know this is an old thread, but I want to thank you for this add-on. I have a question, and I ask it here for the benefit of anyone else who is interested in adding a rotary encoder to a LibreELEC installation.

I find that with each pulse out of the encoder the sound seems to mute before it resumes at the new level. Is this expected behavior? Is there a fix for this? I probably can live with this for my own use, but others may find this objectionable.

edit: I fixed it. Again, for the benefit of anyone else: I'm using a HiFiBerry Amp2, and the use of GPIO 4 will result in the symptom I described above, since that pin will mute the power stage when pulled low. The solution was to use GPIO 14 instead. The addon works beautifully.

tobor