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LCD music display

Legible notes that don't cost a fortune

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The battle to display music has ranged from originally printing & taping hundreds pages together.

To the ridiculously large full sized TV.

To the ridiculously small & expensive tablet.

To the ridiculously small & cheap portable monitor.

The lion kingdom's goal was always a cheap & large 2 page display, replicating the original book format.  The easiest way to get there was 2 monitors in portrait mode.  Cheap portable LCD monitors finally started appearing in 2019, but they weren't really cheap enough to dedicate to nothing but showing music.

The lion kingdom's stock of obsolete laptops finally reached an age where they were never going to be used again & cheap HDMI to LCD converters abounded.  They were the venerable LTN156AT24 & LP156WH4.  They both had 40 pin connectors & LED backlights.  They both ran on 6 bits per channel.  The point had arrived where a dual 15.6" 1366x768 display just might be possible for under $100. 

1366x768 might be just enough resolution to replace paper if the RGB channels were used as pixels & the text was cropped.  It still remaned a much cheaper option than 1920x1080 panels.

The mane problems with these panels are they're really tall & the electronicals take a lot of space.  Besides the HDMI converter, they would need a raspberry pi, HDMI cables, & power supply.

Finding a suitable LCD controller is manely about finding one with the right cable.  All LCD controllers seem to do the same basic conversion from HDMI to a certain number of LVD pairs & they all have a header for powering a backlight inverter.  None of the converters outside China had a 40 pin cable.  They all had 30 pin cables.  The goog finally came up with a bang good match.

https://www.banggood.com/LCD-Controller-Board-40P-8-bit-HD-DVI-VGA-Audio-PC-Module-Kit-For-B156XW02-15_6-Inch-Display-p-1045418.html

This is the same controller board sold by millions of sellers on amazon.com, but it's the only one which specifically shows a matching 40 pin connector & describes entering a 1366x768 6 bit mode.  They're all based on the same Novatek NT68676 chip.


https://www.banggood.com/14Pcs-Universal-FPC-or-LVDS-Display-Cable-Support-For-10-65-Inch-Screen-LCD-Controller-Board-p-1144074.html

https://www.banggood.com/40-Pin-1-Channel-6-Bit-LED-LCD-LVDS-Screen-Cable-For-Display-p-1140430.html

They also have different cables for connecting a converter board to a 40 pin or 30 pin panel.  Presumably they all connect to the same Novatek board.  Sadly, trying different cables by mail ordering from China could take years.

The lion kingdom got lucky & the 40 pin cable worked with the 40 pin connector on the LTN156AT24 & LP156WH4.

Very important information on setting the language of the Novatek menus.

It should be noted the raspberry pi 4B with dual HDMI doesn't work with 1366x768 panels.  It only does 1920x1080, so driving 2 panels took 2 older 1B's.  

A 3D printed stand, power cables, HDMI cables followed.

A highly efficient X11 program made the 1B's run as fast as 4B's.  Giant 14" tall pages from PDF finally returned.

A custom pointing device could be used without a table.

Custom software allows annotating on 1 screen.

It would have been more efficient but expensive to drive everything with a single PC instead of a bag of ancient raspberry pi's.

Page turning buttons.

  • Wishlist

    lion mclionhead02/24/2022 at 04:19 0 comments

    There is a desire to reduce the number of confusers.  3 confusers for audio processing & music display is overkill, taking a lot of space, & taking a lot of power.  The problem is the dual HDMI raspberry pi only supports 1920x1080.  

    It definitely would be better off with a full sized PC, but that's a lot of money for a lion.  Mini PC's with dual HDMI are only $200. 

    https://www.amazon.com/Beelink-MiniS-4-Cores-Processor-Computers/dp/B0B3DYQ693

    With no more raspberry pi's being made, the $200 mini PC is a compelling solution.

    The HDMI to LVD converters take an analog SVGA signal, but this would not allow addressing the RGB cells.  There are ways to go from USB to HDMI output & from SPI to HDMI output but they're all more expensive than a raspberry pi or a full sized PC.

    https://github.com/techtoys/HDMI-Shield/tree/master/Ra8876_Lite

    The lion kingdom was sort of grateful it didn't buy a trackball.  There might be some accuracy to be gained from it, but the mane problem has proven to be space for the trackpad.   1 solution is not to play anything in the upper octaves & use that part for the trackpad.  Another desire with the trackpad is a reset button.

  • The limitations of 1366x768

    lion mclionhead12/27/2021 at 04:15 0 comments

    The limitations of 1366x768 only became obvious in denser Liszt music.  Only by previously knowing what it should sound like is it legible.  The original PDF isn't very legible either.  Maybe there's a smarter way to preserve more details than thresholding & using RGB channels as pixels.  The x dimension is what kills it.  There would have to be a translation of common symbols in the PDF to a library of vector graphics, then precisely positioning & scaling the vector graphics.  Quite an effort with little gain in an age of 4k panels.  If the input pixels alternate horizontally between light & dark between the output pixels, it could force the output pixels to alternate horizontally without regard for position.

    Upgrading to 1920x1080 panels is tempting & would allow everything to run on a single raspberry.  16x9 is not as ideal as 4x3, but there aren't any 4x3 panels.  It would also entail ordering 2 sets of LVD cables.

  • Trackball users

    lion mclionhead12/08/2021 at 20:49 0 comments

    Another strange photo from N Korea of the commander & chief with the cheapest trackball & a 1960's era confuser console.  That just about covers lions ever getting a $25 Logitech trackman, although a $32 Kensington Orbit may happen someday.  The home made touchpad has been just good enough.  It's mane problem is water sensitivity.  It's always been paw held.  Lions have never used the stylus.  The mane trackball need now is a slippery desk which a mouse pad has trouble sticking to.  Having said that, the mouse does work on the bare fake woodgrain.

    A 3rd LCD controller arrived with a balky cable.  The connector has to be pressed just right.  This was the last of the lion kindgom's 1366x768 laptop screens from 2012.  The laptops since then were macbooks & an expensive Asus GL502V with a 1920x1080 panel.

    Another 1 of the LCD panels frequently blacks out & recovers.  All the lion kingdom's HDMI displays occasionally black out & recover.  The internet says this is a problem with the HDMI signal path rather than the LCD driver.

    In order to boost profits, the non profit raspberry pi foundation removed all discussion of 1366x768 not being supported on the 4, but archive.org still has it.

    https://web.archive.org/web/20210228194634/https://www.raspberrypi.org/documentation/configuration/config-txt/pi4-hdmi.md

  • Trackballs won't die

    lion mclionhead06/25/2021 at 21:57 0 comments

    Trackpad finally got its surface mount conversion.  Only 3 bodges were required.

    A bit smaller.  Without a top section, lions tend to grab around the button area to hold it.  How best to hold it is the next problem.  The right paw tends to interfere with the trackpad.  It has evolved into a pawheld trackpad for which there are no commercial examples.  Even the mighty $130 trackpad requires a table.

    The trackball dream still isn't dead.  Finally noticed Ross Guy doesn't use a trackpad but a cheap trackball on his easy chair.

    Thumb scrollers seem to be their most popular model.  Not sure if the smaller trackball is as accurate as the pool ball ones.  The home made trackpad glitches a lot from body parts getting near it.  Any water screws it up.  Keeping the stylus around has been a pain.

  • Zoom function

    lion mclionhead06/22/2021 at 18:07 0 comments

    After a heroic set of pixel manipulation programming, a 3x zoom function was done.  It's toggled by a new right button.

    The zoom can be dragged just like the gimp.  It directly scales everything.  The previews & cursors don't turn into a single pixel outline when they're zoomed.  Drawing is much easier in the zoomed mode.

    Being a low res 1366x768 bitmap of early 1990's vintage requires more accurate pointing.  When lions freepaw text on a PC, they always use a zoom feature.

    The math required to draw arcs was the 1 thing keeping 10 year old lions from ever finishing a paint program. The slope intercept function required to draw lines might have been accessible, but connecting the pythagorean therum to how a confuser draws an arc was impossible.  It's surprising since then how many people encounter a need to write bitmap editors as part of their programming career.

    Annotation routines could be a lot faster.  The circle routine should draw circles from the top down instead of left to right, so the confuser doesn't have to look up a row for every pixel in the circle.  The line routine should fill the outline of the line instead of copying a complete brush image to every point on the line.

    In practice, lions only ever use 1 pixel & 2 pixel brushes.  The biggest impact users see is the speed of the XOR previews.  Row lookups are negligible when drawing XOR previews, compared to the overhead of the X protocol.  They impact final oval drawings, but those are always very small notes.

  • Using the Elan 33059 trackpad over USB

    lion mclionhead06/20/2021 at 20:14 0 comments

    After 2 full days of hacking, the lion kingdom's recycled trackpad successfully communicated with the X server, thus becoming the world's 1st Elan 33059 to communicate with an X server with a PIC2450 as a bridge.

    The USB driver was originally ported from C to assembly by a younger lion when MPlab was for windows only.  Then it was heavily optimized & documented.  The mane effort was porting the improved driver back to C.  

    For the USB driver to work in C, it has to be interrupt driven.  The assembly language version only got away with polling because it was more efficient.  The source code is in  the elan.X directory of the repository, but it's probably not going to be used for annotations.

    It's obviously pretty large with the microcontroller board.  It would need a long 4 wire cable to move the micro somewhere else, but the pad  just senses motion.  To detect button presses, it would need a bundle of extra wires to the micro.  The micro could be moved to a surface mount board so it just has a USB cable.

    The T14_L pin shares the tapping bit so it can't be used.  The T19_RR, T20_RU,  T21_RL, T22_RD pins aren't sent to the status variable at all.  The 1 pin with exclusive use of a status bit is T13_R, so there could be 1 button.  Another idea for zoom is to use the page turn buttons for zooming when in annotation mode.  The GPIO buttons can't be sent to the X server though.

    It's still really clumsy to draw with.  It needs to be covered with a layer of plastic & placed on a table to be functional at all.  It glitches if any body parts get near it.  Using a stylus helps keep body parts away.

    The 1st enclosure was a big old sheet of coroplastic with everything on it.  Connected a button to the PIC18F2450's programming header.

    This could be used without a table.  With a stylus & the right acceleration setting, it was better than a mouse & probably equivalent to a trackball.  A trackball this accurate couldn't be paw held like the Elan.

    The crosshatch pattern on the Elan made it impossible to freepaw straight lines.  Sometimes, it starts permanently glitching until it gets a drop kick.  Freepawing text might have been slightly easier than a mouse, but it definitely needs a zoom feature.  

    The button 

    https://www.banggood.com/Wendao-R13-507-125V-3A-16mm-No-Lock-Self-reset-Switch-Push-Button-OFFON-10pcs-p-1060608.html

    is real bang terrible.  

    The lion kingdom recommends the MHPS2283V for a momentary pushbutton 

    https://www.mouser.com/ProductDetail/Apem/MHPS2283V

    & the MHPS2283 for a manetained pushbutton

    https://www.digikey.com/en/products/detail/apem-inc/MHPS2283/1795387

    They also make a MHPS2283N which is a momentary pushbutton with no click.  It's terrible.

    The trick with the MHPS line is they require a custom button & board mount instead of the screw mount of the bang terrible ones.  That's why they make 3D printers.

  • Annotation attempt 2

    lion mclionhead06/18/2021 at 19:17 0 comments

    So the circular & hollow brushes proved useless & implementing XOR previews for a circular brush was more trouble than it was worth, so in keeping with minimalism, everything went back to a square brush.  Lions seem to recall PC Paint just supporting square brushes.  Helas, the hollow circles don't follow the contours of the XOR preview.

    Circle, disc, box, & line tools arrived.  Lions can appreciate why the Gimp doesn't have XOR previews of all the tools as PC Paint did.  The fast XOR preview entails writing every tool twice, handling corner cases for showing & hiding the XOR previews, making sure the XOR preview matches what's drawn.

    10 year old lions had no clue how to program an oval drawing routine & drawing ovals is still hard, in middle age.  Even the mighty koala paint didn't have an oval drawing routine, only circles.  The easiest way nowadays is to solve the pythagorean therum for every X to get Y on a circle, then scale the Y to get an oval.  To speed it up, it's done with a floating point lookup table.

    The result is the kind of blinking XOR cursors & line filled brush strokes that lions remember of PC Paint on an 8 Mhz Olivetti 24, but on all off 700Mhz.  Maybe it would have been faster on the framebuffer or using SDL.  The brush stroke routine is suboptimal in the limit.  Brush stroke & hollow circle definitely need improvements.  The XOR cursors are all Xorg routines drawing to the frame buffer.

    Instead of a full screen clear button, it has a filled box tool with 1 of the colors being erase.  That has greatly improved erasing to the point of almost completely replacing the erase tool.

    The line, oval tools improved annotating but it's still manely a nightmare.  The low resolution makes precision a lot more important, like it was in the days of 640x400.  Either it needs a zoom function, a way to lock lines on the axes, or a way to selectively decelerate the pointer.  A trackpad won't do the job if it's already hard with a mouse.  Lions believe a trackpad with stylus could be the best pointing device.

  • Annotation attempt 1

    lion mclionhead06/17/2021 at 03:41 0 comments

    A pretty frustrating experience, to be sure.  It's nowhere near as easy with a mouse on a music desk as it was with a pencil or a mouse on a normal desk.  Line, oval, zoom tools might help, but drawing text without a keyboard is hopeless.  Another idea besides writing a paint program from scratch is to boot up the gimp every time the user wants to annotate, but it requires a keyboard & it's even slower.  It's pretty frustrating to not be able to go to a store & try out a trackball.

    The annotation system is a minimal drawing program based on PC Paint.  Vintage software has once again proven useful as the basis for a modern application.  Drawing programs have been the nemesis of lions ever since they tried to program one in childhood but never could finish it.

    The mane showstopper is event compression on the pi is non existent.  It seemed like a good idea to have PC Paint's XORed brush augmented with a crosshair, but it just sits & redraws single pixel mouse movements without event compression.

    The color palette ended up being the 16 original Commodore 64 colors rather than a modern color picker.  The rest is a simplified version of what lions remember of PC Paint.  Drawing is bitmap based.  There's draw & erase with different brush sizes.  There's no lasso, selection, fill, or polygon tool.  There is a foreground & background layer while the original scanned music is untouched.  There are a certain number of undo levels.

    Erasing large areas is pretty rough without a selection tool.  There is a large eraser brush to try to compensate.  The user has to hit the save button to make new annotations appear on both monitors.  It automatically saves when the user exits or loads a new file.

    Despite every effort, it composites the 2 annotation layers in every single page turn.  It would be pretty involved to make it selectively composite the annotation layers only if they're used.  The page turns have dropped back to 13 per second, with annotations & the background pixmaps required for any useful menu system.

  • Software

    lion mclionhead06/13/2021 at 05:37 0 comments

    Making a minimal confuser actually do minimal confusing is a lot harder than it used to be.  For decades, the raspberry pi foundation has labored to run as much as possible as slowly as possible.  With much coercing, it can be made to just run fvwm on X11.  The key commands are

    apt install fvwm

    xinit /usr/bin/fvwm2&

    /usr/share/fvwm/system.fvwm2rc has to be copied from somewhere else.  It needs an option in system.fvwm2rc to disable the reader's window border.

    Style "Reader" NoTitle, HandleWidth 0

    Sadly, the current versions of fvwm no longer support keeping a window on top.  That has to be done in the program.

    Then, there are commands to try to slow down the mouse speed.

    xinput
    xinput --list-props "PixArt USB Optical Mouse"
    xinput --set-prop "PixArt USB Optical Mouse" "libinput Accel Speed" -1

    The lion kingdom believes the mouse speed still needs a kernel hack to be slow enough.

    The server pi needs to export NFS to the client pi so they can access the music files.

    The decision was made to finally make the Cinelerra toolkit a standalone library with the ability to strip out all its video editing features.  It works quite well as a minimal retro interface, only taking 18 minutes to compile on a 1B.  As simple as it is, it's still takes a beast to do all the listbox, textbox, & menu operations a toolkit has to do.

    Since it's not a dual head confuser, the mouse only works on 1 monitor.  It's a bit contorted to have a mouse 3 octaves away from the screen.  It definitely needs a mouse stand on top of the panel.

    Despite all the hype about a pointing device which can draw, annotations are going to slow page turns way down.  In its simplest form, every page would optionally have 2 annotation layers, a foreground & background.  Each layer would have 16 possible colors, including transparent.  The resolution wouldn't be able to use RGB subdivisions.  Annotations would go in a separate file with flat images & flags saying if an image was used.

    It needs to support 1/2 a page turn so every page can be shown on the screen with the pointer.  The client confuser needs to poll the annotation file for updates.  The annotation file needs to be in RAM along with all the music images.  The client would have to reload the entire file when it changed.  To speed this up, the annotation file can start with a table of contents, showing what revision each page is on.  The client can reload just the latest revision of 1 page.

    Then of course, the server needs a full paint program, 1/2 page turn buttons, draw, erase, color palette, layer, save file, brush size, brush type, but no undo is required.  The 2 layers need different color palettes.

    There's still a dream of just running it without RGB subdivisions, on the dual head 4B, with its horrible aliasing.  Page turns with annotations would be a lot faster.  The mouse would work on both screens.  The networking protocol, NFS, half page turns would go away.

  • Stand version 3

    lion mclionhead06/10/2021 at 18:06 0 comments

    A new batch of stands came off the printer.

    Featuring all new latches

    Much easier access to the electronicals.  Farther placement back.  Flaps to keep it from sliding forwards.

    New confuser placement.

    Plans continued for a pointing device.  All attention turned from trackballs back to an old fashioned mouse in the short term, eventually being replaced by a trackpad.

    So the Elan 33059 isn't documented anywhere, but it's similar to a more common Synaptics described on 

    https://www.hackster.io/frank-adams/laptop-touchpad-conversion-to-usb-d70519


    The ribbon cable pinout doesn't match, but the Elan version otherwise has the same signals as the Synaptics.  The test points are even labeled 

    TD - PS2 data

    TC - PS2 clock

    T13_R - right button

    T14_L - left button

    T19_RR - scroll right

    T20_RU - scroll up

    T21_RL - scroll left

    T22_RD - scroll down

    TN - ?

    TP - ?

    Source code is scarce.  The best example was 

    https://www.hackster.io/frank-adams/laptop-touchpad-conversion-to-usb-d70519

    There were comments about the source code working with an Elan chip.  It bit bangs the PS2 pins.  Sadly, a quick test showed TN & TP are not USB pins.  

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Arya wrote 05/25/2021 at 04:52 point

>>> The point had arrived where a dual 15.6" 1366x768 display just might be possible for under $100

Very much so! I'm compiling information on general reuse of these displays here: #All About Laptop Display Reuse , drop by our chatroom anytime!

>>> All LCD controllers seem to do the same basic conversion from HDMI to a certain number of LVD pairs

Yep! The controllers that you mention specifically, M.NT68676 boards, also need to be programmed with the right firmware to drive 1366x768 panels.

>>> describes entering a 1366x768 6 bit mode.

That sounds good, I didn't know that's what "LVDS mode" meant for these controllers, but it makes sense!

What I'd typically recommend is punching your panel number into the eBay search bar, in your case, you'd get this: https://www.ebay.com/itm/353425194982 . I went and checked - both of your panels have the same pinout, driving requirements and color bit mapping scheme, so if you buy 2pcs of this same controller, it should work with both of the panels. Searching for a panel-specific controller helps you avoid cable troubles, and in case of the eBay link I'm sending, it's also going to come out cheaper!

The second cable you're showing seems like the right deal - you definitely don't need a set of 14 different ones! =D However, you don't even need that cable if you're getting a panel-specific controller, since a panel-specific kit will be coming with the right cable already!

Nice project! Added it to #Laptop Display Things list =)

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