A pocket player using a memory card does not have to have a color screen and complex graphical interface. Some models do not have a display at all and are controlled by "blind" buttons. They also find many adherents.
Instructions
Step 1
Take any microcontroller from the following list: ATtiny23, ATtiny45, ATtiny85. Find the archive with the firmware on the page whose address is indicated at the end of the page, and then write to the controller the one that is designed for the usual monophonic version (the stereophonic, as well as the improved monophonic versions take up more microcircuit pins, and therefore require a special version of the programmer while for an ordinary monophonic one, any suitable programmer is enough, even the simplest one).
Step 2
Pin 4 of the microcontroller connect to the common wire, pin 8 - with the power supply plus, pin 2 - with pin 2 of the microSD card holder, pin 6 - with pin 3 of the holder, pin 7 - with pin 5, pin 5 - with pin 7. Pin 6 of the holder connect to the common wire, pin 4 - to the positive of the power supply.
Step 3
Between the common wire and pin 5 of the microcontroller, connect a chain of 4, 7 kOhm resistors and buttons connected in series.
Step 4
Connect a blocking ceramic capacitor of any capacity in parallel with the power supply.
Step 5
Headphones (with parallel-connected emitters and a built-in volume control) connect between the common wire and pin 3 of the microcontroller through a 100 μF electrolytic capacitor connected in series (plus to pin 3, minus to the headphones). For a domestic capacitor, the positive terminal is marked with a plus sign on the body or at the bottom (if it is K50-16), and for the imported one, next to the negative terminal, a strip of minus signs is applied to the plastic shell.
Step 6
Use a card reader to write WAV files to a Micro SD memory card with FAT file system. To convert OGG, MP3, WMA files to it, use Audacity or similar.
Step 7
Connect two AA cells in series with the circuit breaker in correct polarity.
Step 8
Unmount the card, set the volume control on the headphones to minimum, transfer the card to the player and turn it on. It will start playing the first file automatically), then gradually increase the volume to a comfortable level. Press the button to select the next file. To return to the first file, turn off the power briefly.
