Translated from English, device is just a device. But in Russian, devices are mainly called pocket devices: players, smartphones and the like. Some of them can be made by yourself.
Instructions
Step 1
One of the most suitable devices for making at home is the minimalist pocket player. Its only control is a button, and there is no display at all. To manufacture it, purchase an ATTINY25, ATTINY45 or ATTINY85 microcontroller. Follow the link indicated in the additional materials, then download the sd8psrc.zip archive from this page using the Firmware link (Source files + HEX files). Find the HEX file in this archive and program the microcontroller with it.
Step 2
Use the included adapter as a Micro SD card holder. Connect the microcontroller pins to the holder pins in the following order (the first digit is the controller pin, the second is the adapter pin): 2 - 2; 6 - 3; 8 - 4; 7 - 5; 4 - 6; 5 - 7.
Step 3
Connect the compartment for two AA batteries with the positive pole to pin 8 of the microcontroller, and the negative pole to pin 4. Shunt the compartment with a ceramic capacitor of any capacity.
Step 4
Connect the push-button and a few kilo-ohms resistor in series. Connect this chain between the minus of the power supply and pin 5 of the microcontroller.
Step 5
At the headphone jack, connect the terminals corresponding to the left and right channels in parallel and connect through a capacitor with a capacity of about 100 μF (minus to the jack) to pin 3 of the microcontroller. Connect the common contact of the socket to the minus of the power supply. Headphones must have a built-in volume control.
Step 6
The audio files that you want to listen to on the player, transcode into WAV format and rewrite them to a card using a card reader that allows installing microSD cards without using an adapter (it is already used in the player). Immediately after you insert the card and batteries (in the correct polarity) into the player, music will play. Use the button to select the next file. Remove the batteries to stop playback.
