Gained experience, additional details appeared and, most importantly, time!
I decided to make a portable, wearable, audio player.
To begin with, I decided on the case - in my case, the case from the “power bank”, which I am, acted as its role.
Soldered the USB connector and installed it in a regular place in the case, connecting it with a wire.
I installed the microUSB connector in the regular place of the case, soldering to the plus and minus with an enameled wire from the transformer (I will often use it). 
I cut a hole with a drill for the headphone jack and soldered it with enamel. 
I installed a suitable, in size, battery from a 900mAh dialer and determined a place for a charge / discharge control scarf. I installed an LED to indicate the process of charging the battery (green heat shrink). I drilled holes for the speaker and glued the cover with aluminum. I installed a speaker from the dialer in the case cover (the sound is not very good, and the place was back to back, you can’t install a good speaker, but this speaker is more of an indicator that the player is working and reading songs, because it will be listened to all the time in headphones). I cut a groove and installed a microswitch to turn the player on / off. 
It is not visible in the photo, but I will say in my own words - the MP3 board comes from the factory with disgusting output capacitors. For a good sound in headphones, you need to replace them with more capacious ones - 10-200 microfarads, which I did.
I thought about the buttons for a long time, as a result, I came to this option (I made the holes for the conclusions with a heated needle, and then filled it with superglue. 
View from the headphone output side: 
View from above: 
Front view: 
View while charging (I installed a difficult LED and a slow flash LED that changes colors) 
TOTAL: The result is a light, compact, long-playing MP3 player. For convenience, I use a tiny usb flash drive (does not stick out, sticks out a little, but not critical). The slot for memory cards did not install, because. there wasn't enough room.
Operating time at medium volume ~ 30 hours.
Used components:
-$0.50
-$1.61
-$4.59
(did not buy, was from an old phone)
Unfortunately, I didn’t find the case ... I can’t find it on Ali anymore (maybe I was looking badly). But in this review, I wanted to show that you can literally make a portable player from improvised means, and the case in your case can be absolutely anything.
This mp3 player, not quite the usual design, was made from improvised means.
A good solution for giving and at minimal cost. In the course of the general harvest, a lot of rubbish was collected to be thrown away and something that I decided to put into action). The case is made of cardboard from household appliances glued in half, which gives the structure good rigidity. Why cardboard? It is easier to work with it and a lot of it remains after buying household appliances, and in this homemade cardboard is well suited for creating a case.
Step-by-step assembly and demonstration of the mp3 player in a video for review
Was used:
1. Cardboard box from household appliances;
2. Copper wiring from old electronics;
3. 2 speakers from old computer speakers;
4. Keyboard from an old cell phone;
5. Rechargeable battery from an old cell phone;
6. Switch ();
7. 4 screws;
8. Battery charge module ();
9. Mp3 player without case ();
10. Adhesive decorative film;
11. Hot glue, super glue, electrical tape.
From tools:
1. Pliers;
2. Scissors;
3. Stationery knife;
4. Screwdriver;
5. Glue gun;
6. Soldering iron (, very convenient);
7. Third hand.
Making a player
We cut the cardboard into paired pieces, 4 pieces of each size.
1. 4cm x 8cm, 3.6cm x 7.6cm;
2. 4cm x 6.5cm, 3.6cm x 6.1cm;
3. 6.5cm x 8cm, 6.1cm x 7.6cm.
And glue them together. This will give the structure rigidity.
Electronics that will be used in homemade.
Cheap mp3 player with USB and microSD connectors (). Powered by 5v or 3.7v battery. A 3W signal amplifier is already built into it. A voltage stabilizer is also built in. Power connection via microUSB and two battery terminals.
Lithium battery charger module 18650 on TP4056 5V 1A with micro USB interface (). It is suitable for charging batteries from cell phones.
Rechargeable battery Philips 1100mAh. Pulled from a broken phone.
Speakers from old computer speakers.
I recently ordered good quality switches () for the repair of a table lamp. Just one was left.
And a few buttons from the keypad of a broken phone.
We cut out a place for the speaker so that it sits tightly in place.
We glue the base of the case, the side wall with hot glue and try on the future location of the battery.
We glue on the inside with hot glue for reliable fastening.
Considering the future placement of the charge module.
The charge module and the battery will be located in the case of the second column. The player's board and control buttons will be located in the case of the first column.
Cut out holes for USB and microSD connectors on the top of the case.
We solder the standard buttons from the player board. We will place them on the same upper part of the case for ease of management.
Solder the wires to the buttons. I took 4 pairs of wires of different colors, so that later it would be more convenient to solder on the player's board.
We take a decorative film on an adhesive basis (I still have black) and glue parts of the body with it.
It should turn out like this.
We cut a hole for the button on the upper part of the body of the first column and place the control button there.
On the reverse side, we fix it with hot glue for reliability.
We do the same with the rest of the buttons. The top 2 buttons will be responsible for switching tracks and volume, the bottom left is play / pause, and the bottom right is the track repeat button.
It turned out like this.
Now you can solder the wires from the buttons to the player board.
We fill the soldering points with hot-melt adhesive to securely fix the wires. You can collect them in a heap and wrap them with electrical tape so that they do not interfere.
Observing the polarity, solder one pair of wires from the charge module to the battery.
We fasten the speakers to the case with self-tapping screws and fix the self-tapping screws on the back side with hot glue.
We glue the upper part of the case and fix the charge module with hot glue for reliability.
We make slots for the wires going to the first column, fix them with hot glue on the inside and check the operation of the module before attaching the back of the case.
We twist the wires of the two speakers and solder them to the player board, observing the polarity.
Solder the power wires to the player board and to the switch. Observe polarity!
Dangling parts and wires are fixed inside with hot glue. We check the operation of the player before attaching the back of the case.
To fix the speakers to each other and protect the wires, we glue a wide strip of decorative film on both sides.
The result was a book-shaped design, which gives stability and an unusual appearance to this homemade product.
We glue the buttons from the keyboard of the old phone with super glue. Be careful not to glue the control buttons.
You can start the test.
Indication.
- tutorial
This article will tell you how to make a video player from items that can be found in the pantry of any IT specialist. Arduino, Vogue magazine, and the display from Nokia 3310 can be left alone - we won't need them. The presence of a soldering iron is welcome, but you can do without it.
Judging by the speed of technological development, in ten years there will be a generation that has never seen cathode ray tubes. Meanwhile, the history of video displays began with completely different devices ...
History
In 1884, a few years before the invention of radio, a German student, Paul Nipkow, patented the world's first television system. With electronics at that time it was unimportant, therefore, an electromechanical approach was used to build an image: the brightness of a pixel was set by an electric lamp, and its position was set mechanically, using a rotating disk. Holes were made in the disk, arranged in a spiral; thus, when the disk rotated, the holes flying one at a time "scanned" a fixed field of view. And although the inventor himself never created such a system, until the 1930s, the Nipkow disk was popular with other television developers.
On the transmitting side, behind the disk, there was a photocell that estimated the brightness of each point in the image. Rochelle photodetectors of that time had a low sensitivity, so the studio had to be flooded with bright light, and the faces of the announcers were made up with purple paint, just to improve the image quality. In another version, the light sources and detectors changed places: a bright arc lamp was placed behind the disk, and a darkened studio was placed behind the luminous dot; reflected light was captured by a set of photocells.
The viewers, in turn, looked through the Nipkow disk at a neon lamp, the brightness of which was determined by the readings of photocells transmitted from the studio. The picture turned out to be the size of a postage stamp, so a magnifying lens was placed in front of the disk. It is interesting that these images fit into the sound spectrum, and were received by the most ordinary radio receiver. In fact, the TV was a simple set-top box that a village radio amateur could assemble. The main problem was to get neonka - everything else, from marking the disk to winding the electric motor, was done by hand. (In especially neglected cases, instead of an electric motor, a handle was placed, which the viewer had to rotate at a speed of strictly 50 rpm.)
Of course, technology has come a long way in the past eighty years, and no one is surprised by devices like the "3D HD Active Matrix OLED Display" (in the 1930s, by the way, the average person would have understood only the word "organic"). On the other hand, this means that a modern engineer in a pile of old rubbish can find at least a bright “neon” (LED), even a precision stepper motor (in an old CD-ROM), not to mention light and perfectly balanced compact discs...
Assembling a mechanical TV
Although our device will work on recorded signals, and it would be more appropriate to call it a video player, nevertheless, it can also be used to display NBTV TV programs broadcast by some radio amateurs.We need four components:
- Nipkow disc
- Disc rotation motor
- Adjustable light source
- Video source
Nipkow disc
In the thirties, discs were made of cardboard, thin aluminum, or even a paper ring on a wire frame. We will take advantage of the charms of progress and take an unnecessary CD, since there are a lot of them. If there is a choice, it is better to take a disc with a dark surface - this will improve the contrast of the image.
In the last century, marking holes required great accuracy, the ability to handle a protractor, and a special compass for drawing a spiral. We will mark the disk virtually in a graphics editor (for example, Inkscape) and print the finished drawing on a printer. Then we fold the paper along the edges of the printed circle (see photo), and wrap the disk in the resulting paper envelope. The printed image should remain outside, it will serve as a guide for drilling. Happy owners of LightScribe /LabelFlash-enabled drives can print a mask with holes directly on the surface of the disc.
Finally, we take a micro-drill with a 0.6-0.8 mm drill and drill the disk according to the markings. Don't have a micro drill? No problem! The fact is that CDs (but not DVDs!) have an aluminum layer with data protected only by a thin layer of varnish, so they can be carefully scratched with a sharp metal object, such as a screwdriver. There is no need to scratch through, the disc substrate is transparent.
Engine
To be honest, this article was originally conceived as a way to somehow use an old DVD-ROM lying around idle: there is both an engine and a convenient disc holder. However, digging into the topic showed that the drive motor is far from being as simple as we would like: it is multi-phase, uses Hall sensors for feedback, and is controlled by a special microcircuit. Therefore, it was decided to leave experiments with the drive for the future, and use something simpler and more understandable: a computer fan, also known as a cooler.
A USB fan from the famous NoName company turned up as a cooler. A pleasant moment was the dome-shaped cap with blades: the diameter of its base was 22 mm, while the diameter of the central hole of the CD was 15 mm. If you direct the fan vertically upwards, you can put a disc on top, almost like on a gramophone, and most importantly, it does not fall off. To improve grip, a couple of strips of double-sided tape were pasted into the inner hole of the disc (see photo). Unfortunately, the flimsy motor is clearly not designed for a 15-gram load, so it gets quite hot in a couple of minutes of operation. With a larger cooler, this shouldn't be a problem.
Attention: despite its smooth shape and light weight, a broken disc can cause some trouble. And if you overdo it with engine power, the disk may burst, and the fragments will have to be not only collected around the room, but, possibly, picked out of the body. So consult with common sense - the author is not responsible for possible injuries.
Light source
Oddly enough, in 2011 it is no easier to get a neon lamp than in 1930: they are practically not used anymore. Fortunately, one of the LEDs that can be found in any old peripheral device, from a mouse to a printer, is quite suitable for us.
Unfortunately, the LED cannot be connected directly to the audio output: most likely, there will be no glow even at the maximum volume. Therefore, you will have to build a simple amplifier on a single transistor (see diagram). The power source can be either a pair of ordinary batteries (then the resistor can be removed), or USB (red wire - plus, black - minus; a resistor of 500 ohms or less, selected according to brightness). Transistor - any n-p-n type.
If the transistor is plucked out of some device, you can determine its type and pinout using a multimeter: try different combinations of pins until the device shows a number in the range of 30-1000. When this happens, spell next to the pins to determine the location of the legs of the transistor.
If the length of the leads allows, the circuit can be made on twists, although, of course, for the reliability and aesthetics of the connection, it is better to solder. Either way, the exposed leads should be shrink wrapped or wrapped with Blue Tape™ for added durability.
There is one negative point in using an LED instead of a gas lamp: the glow of the semiconductor is “pointy”, and we need to highlight (if possible evenly) a 15x15 mm square. The problem is easily solved by placing a translucent piece of paper over the LED, onto which a spot of light will be projected.
The assembled optical part looks like this: 
The third hand tool is very handy for fixing all the components in the right positions. The lens is optional, it just came with the kit. Instead of a "third hand" you can use the surrounding objects, glue, or the help of colleagues.
Video source
The most accessible signal generator for an IT specialist is a computer sound card. We will use it. Of course, no one bothers to then burn the generated file to an MP3 player and argue with friends that your one-button iPod can play video.To debug the system, I wrote a simple Java program that displays a 22 by 32 pixel image on the sound card. The source can be taken from
Making an mp3 player!
Hi all!!
Today I want to offer you a not quite familiar scheme for this site.
Everyone who reviewed the articles here must have noticed that most of the devices are various lighting installations, which, for the most part, are based on microcontrollers and a bunch of LEDs.
In this article I will tell you how you can assemble a compact, autonomous and fully functional mp3 player at home, without the use of professional equipment.
So, a little about the device:
Pros:
+ reads mp3 files from SD/MMC/MicroSD cards up to 2 gigabytes (all existing bitrates (up to 320 kbps inclusive));
+ The sound quality is very good for me. There may not be an equalizer per se (only one button that boosts the bass by 15 decibels), but it's enough;
+ consumption of 5-6 mA, that is, with a regular Li-Po battery 1000 mAh, it will work 16-20 hours;
Minuses:
- no rewind and track time is not displayed;
- the battery charge level does not always work correctly;
- it may seem to some that it is not so compact;
P.S. - yes, forget about all these minuses, because no matter how "imperfect" the player is, you will make it yourself and let someone just try to tell you something!
So, more to the point. Let's study the diagram:
At first glance, everything is not so simple. Here I "conjured" a little on this picture in Paint and here is the very scheme, but with my comments and corrections:
By the way, who does not know, AGND and DGND are grounds that need to be connected directly near the power source - that is, right next to the wire that comes from the battery.
I think everything else is clear.
So what do we need:
All microcircuits, microcontrollers, resistors, capacitors, coils, quartz (at 16m and 20 MHz), diodes, as well as USB mini and 3.5mm (for headphones) connectors. Also, do not forget about the screen (ls020). To do this, we need to buy any Siemens phone of the 65th series (s65; m65; cx65); 
Personally, I bought a used cx65 phone (it even turned out to be working). Removing the screen was not difficult. 
2. We also need a soldering iron 30-40 watts, liquid and solid rosin;
3. For soldering ATmega128, VS1011E, you can use a hot air gun, or you can solder it manually, using a screen from an old antenna wire. This soldering method is clearly demonstrated in this video:
That seems to be all. Although ... I forgot the most important thing that you need is 2-3 days of free time, patience and direct hands: D
Well, let's get started. We cut out a rectangular piece ~ 74x70 mm in size from a double-sided textolite. BUT! This is a printable version with a MAX756 power supply and a 3.3 volt power regulator (LM1117). Later, I decided to use lp2981 (3.3), because it is much smaller and cheaper and the efficiency is almost 100%. Therefore, if you wish, you can redo the board (but do not forget that you will need to mount the battery somewhere else! Using the Layout 6.0 program, open the file "mp3 on ATMega128 and VS1011E (with an adapter) Under print.lay" press "Print" and select the following print options:
We print on a laser printer using paper from some kind of calendar or magazine (generally, glossy)
The next step is to drill any 3-4 holes (preferably near the edges of the board). Then we take a piece of paper with the left board and with a needle we pierce those holes that correspond to the holes on the textolite. And we try to compare them as accurately as possible. We transfer the other side of the board to the PCB using the same method. By the way, if the layers almost coincide, it's not scary. There, according to the situation, it will be possible to slightly shift the jumper or something like that.
After that, we hook the board for those holes and poison it. After etching, we wash off the powder from the printer with acetone and get a board. We tin it (I personally tinned it with liquid rosin with a soldering iron, and then washed it with alcohol, but it is also possible with the help of Rosé's alloy).
We solder ATmega128, quartz 16MHz, 22 peaks from the legs of the quartz to the ground. You also need to ground the output of the reset through 0.1 microfarads and connect it to the plus after 10k. Make sure that + and - are applied to all the necessary legs. Check out my diagram.
We connect the programmer, stick it into the computer. Open PonyProg or CodeVision and use them to open the firmware file "MP3_PLAYER_BETA.hex". We are sewing. We set the fuses like this: we do not program anything, except for SUT0, BOOTSZ1, BOOTSZ0.
Got it sorted out. Now we need to take care of the backlight. The backlight here is assembled on the ATtiny25 microcontroller (originally it was ATtiny15l, but now it is no longer available ... if you already have one, write to me by mail, I will send you the firmware for it). It is already easier to connect it to the programmer: we connect MISO, MOSI, SCK, RESET, VCC, GND according to the datasheet. We flash the file "DCDC25.hex". ATTENTION! We do not touch fuses at all! We leave the factory settings.
We solder it to the board with diodes and conduits and check the backlight:
Well, now a few words about soldering vs1011E. For you to understand, the adapter will be on the side of the ATmega128.
Therefore, we need to drill only those holes into which the "leg" of the DIP package will be inserted, which goes to the other side of the board. These are 4, 16, 20, 21, 22, 39, 42 and 46 conclusions. Solder all other jumpers directly to the tracks from the side of the adapter. To unused legs, the jumper will not be inserted into the adapter at all. After that, solder the vs1011E decoder into the adapter and insert it so that the corresponding jumpers go where they need to. Further very fast but careful solder the adapter. Why fast? Because you can heat the jumper too much and it will fall off the board. It will probably be hard to fix...
After that you can turn it on. In general, the player can also work from 16 MHz .. but then it will not play mp3 with a bit rate of more than 256 kbps. To do this, the microcontroller needs to be overclocked. This is pretty easy to do. The first option: gradually increase the frequency (first 16 MHz, turned on, turned off, then 17 ... and so on up to 20.). Another method tested by me: I did not have only three quartz frequencies: 16, 18 and 20. 16 - the player works, 18 - the player works, 20 - nothing. At first I thought that everything more than 18 would not work ... but here's an idea: I turned on the player at 18 megahertz quartz, turned on the song, it plays .. and I solder 18 right on the go and fix 20 - voila, after rebooting the player plows !! At the same time, it would not hurt to remove the matching conduits (from the quartz legs to the ground), because personally they only caused interference for me, and with 20 MHz quartz, the player did not turn on at all. Well, one more remark to the "primitive" bp circuit. The quartz was replaced before its change, and with the advent of the new operating frequency, the player began to experience a bunch of glitches - from white squares on the screen to a complete stop of work ... everything went away with lp2981) Well, I seem to have told everything I wanted))
By the way, important announcement. Immediately I say that the author of the firmware is not me. It has already been featured here:
https://service4u.narod.ru/html/mp3.html
It's just that when I got to that site, I immediately wanted to assemble it, but ... the problem was that I had never collected such complex schemes and for me there was a lot of incomprehensible ... I climbed Google for a long time, looking for topics about microcontrollers, created forums, asked this and that ... also corresponded with the author of the above site. In short, there were worries. Here I "chewed" everything for you and I think that after this article you will have no questions left. Well, if they do, then write to the mail [email protected]. And one more thing I wanted to say... anyone can collect such an mp3. After all, at the moment I am only 14 years old and this is only my second circuit on a microcontroller, and the first one was not successful ... it was also the first time I worked with such small microcircuits and details, in general. After all, here I soldered a microcircuit less than 1x1cm in size and with 48 pins, given that before that the most complex microcircuit that I met was a 20-pin DIP package. That's it.
So go ahead, collect, the result will be stunning: DD
P.S. (all seals and firmware in the archive below)
Well, what kind of article would it be without a photo of the final type of device and a video presentation of assembly and work)) 
Video presentation of assembly-work (not with the newest photos):
My cat appreciated it, I hope you will be satisfied too! 
Good luck!
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A typical schematic diagram of industrial and homemade MP3 players is shown in the figures below.
According to the block diagram, information entering the player in analog form is fed to an analog-to-digital converter (ADC), with the help of which the analog signal is converted into digital form in real time, after which it is written to the flash memory chip. In addition to analog form, audio information can be entered into the audio player in digital form from a computer. To control the built-in memory block, appropriate microcircuits are used, which carry out the necessary transformations related to information compression. The recorded information is stored in the player indefinitely, regardless of the state of the batteries, thanks to the use of non-volatile memory.
The basis of the scheme of any MP3 player is the processor and the memory unit. Under the control of the processor core, information is received in analog form to the ADC, which is part of the processor chip. Before entering the ADC, to ensure the correctness of the conversion, the analog signal is filtered. After conversion, the signal is digitally recorded in a memory module represented by flash memory chips. The same analog signal comes from a microphone or FM radio.
Audio information can be entered into the audio player and in digital form from a computer via the USB interface. When playing music, the digitally recorded data with the memory controllers is read from the media being used. They go to the DAC, where the analog signal is restored from the digital form of representation. The signal is then amplified to the desired level, sufficient to be played through headphones or a speaker.
The quality of the reproduced music is determined by information processing algorithms. A typical MP3 player is controlled by miniature buttons (sometimes touch sensitive) and has a built-in LCD display. Memory capacity - 1 - 16 GB, all models support USB2 interface. Power is supplied either from a standard AAA battery, or most often from a built-in lithium ion (polymer)
