LCD music display

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.

Project Logs

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Updated screen offerings
lion mclionhead • 12/07/2023 at 19:29 • 0 comments

https://us.espres.so/products/espresso-pro

This is a 17" 4k, portable display which would bring back the ability to directly write on music with the required accuracy. The height is 15.6". The historic height of staff paper is 12" but 15.6" is the smallest with 4k.

Of course, you'd have to be stupid to pay that much & it would take 2 monitors to fully to the job but it showed considerable improvement in portable monitor offerings.

There's 2560x1600 in a 16" without touch.

The pride of China is a 15.6" with touch & 4k.

Then for the same price of 2560x1600 is 4k from another brand. Lions doubt the truth of some of these chinese deals.

https://www.walmart.com/ip/XGaming-16-120Hz-Portable-Gaming-Monitor-2-5K-2560x1600p-QHD-IPS-Laptop-Monitor-Dual-Type-C-Mini-HDMI-HDR-PC-Mac-Phone-Xbox-PS4-PS5-Smart-Cover/2341421537

Then there's a Walmart deal. 2560x1600 might be the sweet spot.

Lions couldn't justify upgrading the current music display, given its level of use & how 1366x768 has been just good enough. 1366x768 would definitely be enough for composition. The higher resolution would only be needed for annotations, more serious playing, or maybe a more expensive instrument.
Annotation Busted
lion mclionhead • 06/14/2023 at 23:09 • 0 comments

Annotating music with this system has proven to be a dumpster fire. Despite every effort with the zoom feature & the stylus, it just doesn't work. The mane problem is the resolution is too low. Even 1080x1920 wouldn't be high enough resolution to simulate writing tiny numbers on paper. Every pixel has to count so cursor movements are real slow, trying to hit the exact pixel. Drawing accurate lines with fat pixels is real hard. Constraining to certain angles might be necessary.

The zoom level makes a slight difference, but it still feels like the cursor is always on the edge of 2 pixels & you have to move very slowly to hit the right pixel. The stylus isn't as smooth as hoped. It sticks & stutters along. It's not much better than drawing with a joystick in 1984.

The line tool is slow but accurate for drawing text. The pencil tool can draw slightly faster but very messy text. The circle tools are essential for drawing notes, but it's real hard with fat pixels. The pencil tool has only been useful for drawing dots. Hollow & filled ellipses for the pencil tool might make it faster for drawing notes than the circle tool. A virtual keyboard & a text tool seem to be the biggest need.

Maybe a capacitive touch screen should replace the track pad, but that's an expensive proposition. It might be time to reconsider a trackball. There's also going with a small mouse or using a phone screen as a track pad.

This system might still have potential for notation capture, since that doesn't involve any manual drawing. The sizes of all the symbols can be fixed, so the precise positioning of fat pixels can be automated.
Fixing NFS
lion mclionhead • 12/08/2022 at 00:02 • 0 comments

The immediate desire was getting rid of NFS & sending the score inside the load command. That way rebooting doesn't need to involve mounting NFS before starting the program. It would be simpler than configuring autofs. The raspberry pi's have to automatically start the reader & mount the filesystem, since they crash every time the LCD panels are unplugged & the power supply is a trashed 10 year old Dell. The problem with this is the annotations & score are separate files. They're both gzipped. The command packets are structured around single byte codes rather than sending a complete file.

This makes autofs the easiest way. Past experience making virtual filesystems showed it's always easier to use NFS for sharing files than trying to make a custom solution.

Autofs begins by editing /etc/auto.master. Uncomment the following line:

/misc /etc/auto.misc

Then edit /etc/auto.misc & add a line for the filesystem to mount

reader -rw,insecure,nohide,async,no_root_squash,anonuid=0 pi:/reader

Then restart autofs

service autofs restart

The problem with autofs is all the filesystems have to be mounted inside /misc. It can't mount anything inside /. You have to ln -s /misc/reader /reader to get a filesystem to appear under /

Sadly, despite this level of automation, it still takes several minutes for autofs to access the filesystem after a reboot of the server. The reader locks up for several minutes during that 1st load. Rebooting the client goes fast.

Using dual 800Mhz raspberry pi's has been less than ideal. The mane problem is it takes a real long time to load a score & save a score after annotating. Page turning is fast. The pi's also don't have a sleep mode, so they're getting expensive to keep on all day.
Wishlist
lion mclionhead • 02/24/2022 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 mclionhead • 12/27/2021 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 mclionhead • 12/08/2021 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 mclionhead • 06/25/2021 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 mclionhead • 06/22/2021 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 mclionhead • 06/20/2021 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 mclionhead • 06/18/2021 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.