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  1. #1
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    May 2008
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    Melbourne, Australia
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    Preamplifier project - Help with PcP to display images

    Hi,
    Hoping for some help (linux noob) not sure if this should be posted in "DIY" or here, but as it's PCP related...
    I'm planning a building a stereo preamp with built in PCP on RPi 4b running Jivelite and display.

    Control of PCP will be through iPeng/Web/Duet so not looking to add touch screen or encoder/buttons (well maybe...)
    I have succesfully managed to get PCP working on RPi 4b with a number of displays so good there.

    What I would like is when the preamp input selector is on an input that is not PCP to display a "PNG" file stored on the SD card (i'e CD, Phono, Casette etc).
    These could be pretty simple (2 tone) or possibly low depth colour, or even animated (rotating cassette hubs?)

    For the selector I plan to use a BCD encoded switch driving a BCD controlled relay PCB to switch the audio inputs.
    I think this is a neat solution and provides a BCD input that can be wired to the Pi GPIO pins.
    Volume would be in the analog domain (that's easiest for me).

    I don't have the Linux skills to add the required packages and scripts to the PCP 8.0 image I have running.
    However I'm sure it can be done with the requisite skills.

    Possible enhancements I've already thought of...
    I use digital radio a lot and the images that are associated with some stations are either missing - or I would rather create a logo.
    I store my radios under "favorites" so if the same concept - to display a PNG (or other graphic) according to favorite selected?

    Also, speaking of favorites. Maybe I do want an encoder added - to select favorites from the front panel.

    Also, there are USB controlled relay boards as well as RS485 etc. These are all options.

    Here's a mock up of what I'm thinking:
    Name:  MFW6.png
Views: 348
Size:  11.3 KB

    Very grateful for any ideas/help.

    thanks,
    Matt Walker
    Melbourne, Australia
    piCore Player 7 on Raspberry pi 4b

  2. #2
    Senior Member
    Join Date
    Jul 2020
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    299
    Quote Originally Posted by mfwalker1 View Post
    Hi,
    I don't have the Linux skills to add the required packages and scripts to the PCP 8.0 image I have running.
    However I'm sure it can be done with the requisite skills.
    Maybe somebody with better skills might disagree, but I don't think what you'r trying to do is possible like this. Your first challenge would be to get PcP to somehow sense the position of your switch (can you add an output to connect to the Pi?) but then getting JiveLite to display something based on that info strikes me as rather complicated...

    Would a different design be an option? Using a second Pi as a controller that takes the input from the switch and then triggers the relay and displays the images? If the controller Pi runs a browser you could then also have it display the Material now playing screen when the input is set to LMS. Though still not an easy project that seems more doable to me..

  3. #3
    Senior Member
    Join Date
    Feb 2011
    Location
    Cheshire, UK
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    6,234
    Quote Originally Posted by mfwalker1 View Post
    Hi,
    Hoping for some help (linux noob) not sure if this should be posted in "DIY" or here, but as it's PCP related...
    I'm planning a building a stereo preamp with built in PCP on RPi 4b running Jivelite and display.

    Control of PCP will be through iPeng/Web/Duet so not looking to add touch screen or encoder/buttons (well maybe...)
    I have succesfully managed to get PCP working on RPi 4b with a number of displays so good there.

    What I would like is when the preamp input selector is on an input that is not PCP to display a "PNG" file stored on the SD card (i'e CD, Phono, Casette etc).
    These could be pretty simple (2 tone) or possibly low depth colour, or even animated (rotating cassette hubs?)

    For the selector I plan to use a BCD encoded switch driving a BCD controlled relay PCB to switch the audio inputs.
    I think this is a neat solution and provides a BCD input that can be wired to the Pi GPIO pins.
    Volume would be in the analog domain (that's easiest for me).

    I don't have the Linux skills to add the required packages and scripts to the PCP 8.0 image I have running.
    However I'm sure it can be done with the requisite skills.

    Possible enhancements I've already thought of...
    I use digital radio a lot and the images that are associated with some stations are either missing - or I would rather create a logo.
    I store my radios under "favorites" so if the same concept - to display a PNG (or other graphic) according to favorite selected?

    Also, speaking of favorites. Maybe I do want an encoder added - to select favorites from the front panel.

    Also, there are USB controlled relay boards as well as RS485 etc. These are all options.

    Here's a mock up of what I'm thinking:
    Name:  MFW6.png
Views: 348
Size:  11.3 KB

    Very grateful for any ideas/help.

    thanks,
    Matt Walker
    Answering only the question about images for favourites.
    Look at favourites.opml (when LMS is off). The img= bit will accept a url or you can drop a png into the LMS file store.
    Canĺt recall the locations of either file or image location off the top of my head but they are easy to find
    Jim
    https://jukeradio.double6.net


    VB2.4 storage QNAP TS419p (NFS)
    Living Room Joggler & Pi4/Khadas -> Onkyo TXNR686 -> Celestion F20s
    Office Joggler & Pi3 -> Denon RCD N8 -> Celestion F10s
    Dining Room SB Radio
    Bedroom (Bedside) Pi Zero+DAC ->ToppingTP21 ->AKG Headphones
    Bedroom (TV) & Bathroom SB Touch ->Denon AVR ->Mordaunt Short M10s + Kef ceiling speakers
    Guest Room Joggler > Topping Amp -> Wharfedale Modus Cubes

  4. #4
    Member
    Join Date
    May 2008
    Location
    Melbourne, Australia
    Posts
    33
    Quote Originally Posted by d6jg View Post
    Answering only the question about images for favourites.
    Look at favourites.opml (when LMS is off). The img= bit will accept a url or you can drop a png into the LMS file store.
    Canĺt recall the locations of either file or image location off the top of my head but they are easy to find
    Thanks, I'll try looking at the favorites.opml to see if I can associate an image with a favorite.

    As for the controller bit. I'm changing thoughts on it.
    Maybe not a BCD output rotary switch, but a plain old 6T2P rotary switch grounding the input relays, with the second pole connecteds to GPIOs to drive the image display.
    I am assuming geting an image to display (for inputs 2-5) would be outside of Jivelite (which may or may not be running) and more to do with a TinyCore script.
    Position 1 would display the Jivelite output.

    Perhaps. Sorry it's above my knowledge.

    Regards,
    Matt Walker
    Melbourne, Australia
    piCore Player 7 on Raspberry pi 4b

  5. #5
    Senior Member
    Join Date
    Aug 2012
    Location
    Austria
    Posts
    1,236
    I'm not aware of anything supporting this out of the box.
    The first basic building block you'll need is a component which can execute actions based on events (key press, position change) from your input devices (e.g. switches, selectors).
    If the input device is supported by the Linux input subsystem (e.g. a rotary encoder), you can use something like triggerhappy. USB devices are usually simpler to work with (e.g. I use a USB DAC with HW volume buttons, which send USB keyboard events, which triggerhappy can process)
    If it isn't, you'll probably have to script something yourself (example) to read e.g. the selector position and execute an action.
    Various SW: Web Interface | Text Interface | Playlist Editor / Generator | Music Classification | Similar Music | Announce | EventTrigger | Ambient Noise Mixer | DB Optimizer | Image Enhancer | Chiptunes | LMSlib2go | ...
    Various HowTos: build a self-contained LMS | Bluetooth/ALSA | Control LMS with any device | ...

  6. #6
    Senior Member
    Join Date
    Apr 2006
    Location
    Oxfordshire, UK
    Posts
    114
    I too have been thinking of something like this. I┬ĺm a big fan of traditional controls even if they are digital behind the scenes.

    Although you have mentioned control via ipeng etc. If you implement a touchscreen it makes navigation very simple while standing in front of the unit so a no brainer.

    I see the Pi as the control system for external audio, not to digitise sources and feed them through the system although I can see some wanting to digitise it at source.

    source selection. Hw = relay selector, pCP icons on front screen, SW to link it together
    volume control. Hw = electronic volume control, pCP has fixed output with volume controls redirected to electronic volume control.

    Hw interfacing there are a lot of I2C interfaces out there

    I┬ĺd also love for the visual meters to be mapped but I guess that would be very hard as the incoming audio from other sources would have to be digitised by the Pi.

  7. #7
    Junior Member
    Join Date
    Oct 2021
    Posts
    1
    I wanted something similar and came up with a "ghetto style solution" ;-) using the screensaver function for displaying a cassette image, when the player is not in use. This can be used for several images as a screen show as well.

    I put one of my players with a 3,5" display into a stripped mid size technics case and another one into a Kenwood Tape Deck I picked out of a recycling box. Using knobs and dials would be nice, but I didn't manage (so far ;-)) how to do that. I was thinking of using an USB game controller for basic functions like play, stop, skip.

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