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The Sony DIY Retro MP3 Player is a community electronics project built around Sony’s Spresense development boards—not a Sony Walkman or retail music player. Published by Shahariar on Hackster.io on March 15, 2019, it combines a microSD-based MP3 player with five physical buttons and a four-digit display. It is a useful embedded-audio project, but its old software dependencies, voltage-sensitive wiring, and known bugs make it a project to reproduce carefully rather than a turnkey 2026 build.
What the project does—and what it does not
The “Sony” in the name refers to the Spresense development platform. “Retro” describes the numeric seven-segment display and tactile controls; it is not an official Sony product category. The original build plays numbered MP3 files from a microSD card and provides play/stop, previous/next track, and volume up/down controls. The project author describes it as a starting point for audio-control applications, not a replacement for a commercial player. The original Hackster project includes its parts list, wiring, code, and version notes.
The published implementation does not provide Bluetooth, streaming, playlists, filename browsing, metadata display, or automatic track discovery. A microphone appears in the hardware list, but recording software was not implemented. USB mass-storage code is commented out because the author reported a play/stop bug when it was enabled.
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The build has several categories of components. The original project page is the authoritative source for its specific shopping list; it contains duplicate or differently described entries, so treat this as a functional checklist rather than a verified substitute-by-substitute bill of materials.
#1 Best Overall
- Large Capacity: This mp3 player is designed specifically for music enthusiasts. It has 64GB storage space, which can easily hold thousands of songs, and supports TF card expansion up to 128GB, so you don't need to change songs frequently or worry about insufficient storage space. (TF card is sold separately)
- The latest version of bluetooth : mp3 player Equipped with the latest version of Bluetooth 5.3 MP3 player, which has better compatibility, signal stability, lower power consumption, longer connection distance, and stronger anti-interference ability. (Note: Bluetooth function only supports Bluetooth headset and Bluetooth speaker connection)
- Easy to operate buttons: This reproductor mp3 has several intuitive buttons. Short press “One-Key Sound” can open the music mode, support breakpoint replay function, continue to play from the last exit position; independent volume key can be up and down toggle the precise adjustment of the volume; Short press “Lock Key” can lock the screen, simple and convenient.
- High quality speakers:MP3 player Equipped with high-quality speakers that deliver clear, undistorted sound. No need to wear headphones, you can enjoy music, listen to books or play recording files directly through the speakers. Whether you're relaxing at home, traveling outdoors or sharing music with friends, the speakers will meet your listening needs.
- Upgraded design: MP3 player Length 4.25 inches (10.85 cm), width 1.95 inches (4.96 cm), thickness 0.37 inches (0.95 cm), weight 80.7 grams, equipped with a 2.4-inch color screen to enhance the visual experience and ease of operation; metal alloy shell both durability and comfortable feel, fashionable appearance to adapt to the sports, commuting, travel and other scenarios, carry no burden.
| Category | What the build calls for |
|---|---|
| Core boards | Sony Spresense main board and extension board |
| Interface | Four-digit SparkFun seven-segment “bubble” display; five 12 mm momentary pushbuttons |
| Construction | Approximately 6 × 4 cm double-sided protoboard, male and female headers, soldering equipment |
| Button network | Resistors including approximately 1 kΩ, 2.2 kΩ, 4.7 kΩ, 10 kΩ, and 22 kΩ values; 1N4007 diode |
| Playback | microSD card, headphones or compatible audio output, USB 2.0 data cable, and 5 V / 500 mA USB power source |
| Optional input | Electret microphone breakout; the original code does not implement recording |
| Software | Arduino IDE, Spresense board support, the project code, and the referenced SevSeg library and BIN files |
The main board supplies the processing and GPIO; the extension board provides the microSD slot and headphone/audio interfaces used by the design. Sony’s current Spresense specifications describe the boards and interfaces. The main board is listed as a six-core ARM Cortex-M4F platform with a maximum 156 MHz clock, 1.5 MB SRAM, and 8 MB flash. Sony’s product listings direct buyers to regional resellers, so stock should be checked locally rather than assumed.
How the hardware is organized
The Spresense main board runs the control and playback code. The extension board handles the card and audio connections. The four-digit display is driven from 12 GPIO lines, while the five buttons share one analog input through a resistor network. That arrangement saves GPIO pins but makes button recognition dependent on measured voltage ranges.
Display pin map
The project code assigns the display pins as follows:
Rank #2
- 【64GB BUILT-IN LARGE STORAGE CAPACITY】Different from other large memory MP3 players on the market, the AGPTEK M3 boasts an impressive 64GB of internal storage, can expandable 128GB memory card (total up to 192G). [Other brands have no built-in memory and can only be used with TF card.]【Tip: The file size of a single transfer should not exceed 3GB to ensure the transfer speed and stability.】
- 【Bluetooth 5.3 & Automatic Reconnection】AGPTEK M3 MP3 music player adopts Bluetooth 5.3 technology, more stable connection, better compatibility, and lower consumption. You can pair the Bluetooth MP3 Player with wireless headphones or a Bluetooth speaker, automatically connects to the last Bluetooth device it was connected to, as soon as it is activated.
- 【HiFi Lossless Sound & Sports Partner】 With a professional audio decoding chip and smart noise reduction chip, AGPTEK MP3 player brings you original lossless music. With breakpoint resume function, perfect for doing sports, Yoga, exercise, running, travel, etc. Supports music formats like MP3/APE/FLAC/WMA/WAV/AAC [Note It does not directly support Audible, Apple music and iTunes.]
- 【Multi-function & Long battery life】 M3 MP3 player with Music Play, Video, Recording, Radio, Pictures, e-Books, Pedometer, A-B repeat, etc. Built-in 500mAh battery, it only takes 2.5 hours to fully charge and enjoy long hours of music. Perfect solution to replace mobile phone music, save mobile phone power. (To save power, the player will automatically power off after 5 minute of inactivity. You can turn it off in the settings.)
- 【 2.4'' SCREEN & LINE-IN FUNCTION】Features a 2.4-inch TFT color screen, bringing a clear and beautiful display. Metal middle frame with ABS plastic back shell,the size is approximately 4.4 inches × 2.06 inches × 0.39 inches, Weight: approximately 3.6 oz. And it supports Line-in recording and playback capabilities. Use a LINE IN cable to record from two MP3 players or connect with other devices for recording or play music.
| Display connection | Spresense pin |
|---|---|
| Digit 1 | D16 |
| Digit 2 | D25 |
| Digit 3 | D19 |
| Digit 4 | D21 |
| Segment A | D23 |
| Segment B | D24 |
| Segment C | D18 |
| Segment D | D27 |
| Segment E | D17 |
| Segment F | D26 |
| Segment G | D28 |
| Decimal point | D20 |
D22 is not used. The author selected a display intended for the main board’s 1.8 V I/O. Do not connect an arbitrary 5 V display or module directly: check its logic-voltage and current requirements and use suitable interfacing or a driver if needed. This is an electrical compatibility constraint, not just a matter of whether the display lights.
Five buttons on one analog input
Each button creates a different voltage through resistor combinations, and the code reads the resulting value from A3. The project describes an ADC range of 0–0.7 V represented by readings from 0 to 1023. Its approximate command windows are:
- 740–790: play/stop
- 400–450: volume up
- 240–300: volume down
- 650–700: previous track
- 550–600: next track
The circuit uses resistor values around 1 kΩ, 2.2 kΩ, 4.7 kΩ, 10 kΩ, and 22 kΩ, with a 10 kΩ pulldown. These code thresholds are build-specific, not universal ADC constants. Resistor tolerance, wiring, board behavior, and supply conditions can shift readings. Log actual analogRead(A3) values on your assembled device and tune the ranges rather than assuming the published windows will match exactly.
Rank #3
- ★【64GB Large Storage & HIFI Lossless Sound】 Each MP3 Player is equipped with a 64GB large-capacity TF card, which allows you to download thousands of your favorite music. And through the powerful DSP audio decoder chip, the most original sound is presented to you. It can ensure the high sound quality of HIFI.（Supports TF cards up to 256GB.）
- ★【Upgraded Bluetooth 5.2 & Support Multiple Formats】 Latest Version Bluetooth 5.2 means that faster transmission speed, longer connection distance and stronger anti-interference ability.Reduced power consumption for more power savings. And support APE / FLAC / WMA / MP3 / ACELP and other lossless formats.
- ★【Built-in HD Speaker & Easy to Carry】 The MP3 player has built-in HD speakers, which can play music without earphones, and no longer need to feel the pain of wearing earphones. MP3 player length is 3.6", width is 1.7" and thickness is 0.35". The body is made of hard and light zinc alloy and weighs only 70 grams. Lightweight and easy to carry.
- ★【Multifunctional MP3 Player for Many Occasions】 Multiple functions in one, music play, FM radio (need to insert a wired headphones), voice recorder, e-book, Alarm clock. Touch buttons with backlight to solve the problem of button noise. Perfect for Sport, Sleeping, Reading, Leaning, Meeting etc.
- ★【Great Gift】Each package contains an MP3 player, wired earphones, a 64GB TF card, a card reader, and a Type-C data cable. It makes an ideal gift for your children, partner, parents, or family on birthdays, Christmas, Thanksgiving, and other special occasions. If you have any questions, feel free to contact us anytime.
How playback and track selection work
The code uses the Spresense SD and audio libraries along with SevSeg:
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#include <Audio.h>
#include "SevSeg.h"It initializes audio, selects the headphone/line-out path, opens a track from the microSD card, writes audio frames, and starts playback. Files are expected to be numbered consecutively—1.mp3, 2.mp3, 3.mp3, and so on. The code sets track_max to 6, so a larger library requires changing that limit or rewriting the file-selection logic. A missing number can lead to a failed open or invalid file handle; a limit set too low prevents later tracks from being reached, while one set too high points the player at nonexistent files.
The author recommends MP3 files encoded at 192 kbps and reports that lower bitrates played at faster tempo in this build. Treat that as a report about this project, not a general Spresense rule. Test the files you intend to use; the available project information does not establish universal behavior across constant and variable bitrate files, sample rates, stereo/mono encodings, or encoders. Track loading is reported to take about two seconds.
Rank #4
- 【32GB Large Storage】The portable MP3 player comes with a 32 GB memory SD card and support up to 128GB(not included). Play music with MP3/Voice record/FM Radio/E-book support TXT format/ photo view / video with AMV format.
- 【Easily to Operate 】Designed with Independent Volume Control, Give you a more user-friendly experience.Can also be used as a memory Card reader or for file storage;Built in high speed Mini USB 2.0 cables,Just drag and drop the music file or folder directly when connecting to computer.
- 【HIFI Lossless Sound Quality】It adopts professional intelligent digital noise reduction chip and superb circuit optimization technology to reduce noise, ensuring high sound sampling rate and providing high quality sound.
- 【Long Battery Life&Portable and Lightweight】MP3 player allows you enjoy real lossless music up to 10 hours. And it fully charged within 1-2 hours. Economy and fashion Noise canceling Voice Recorder; Simple files management.Fashionable and exquisite appearance,Perfect for your entertainment and learning,outdoor and gym fitness.
- 【12 Month Warranty】We have a professional after-sales service team. If you encounter any problems, please feel free to contact us directly and you will get a quick response and a satisfactory response. Your satisfaction is our only pursuit.
The source describes a 50-step volume control, with code adjusting the value in increments of 20. This is a stepped software setting, not a calibrated loudness scale or a guarantee of 50 perceptually even volume levels. The project author tested with headphones because the speaker was broken, so use headphones first and confirm output requirements before attaching a speaker.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Software setup and 2026 compatibility
The original instructions specify Spresense Board Library 1.1.3 and recommend bootloader 1.1.3 or earlier; the author warns that bootloader 1.2.0 was buggy for this project. These are historical project requirements, not confirmation that the old setup is Sony’s current recommendation. Sony’s current Spresense site has updated development-environment information and notes that Windows support is moving toward Windows 11 after Windows 10 support ends. A present-day reproduction may require version pinning or code/toolchain changes; it has not been established here as a copy-and-upload build on current tools.
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The original software package references the project code, BIN.zip, SevSeg.zip, and a bootloader package. The project says to copy the extracted BIN folder to the microSD root alongside the MP3 tracks. Follow the original page’s board setup and file instructions if reproducing its exact version, and consult Sony’s current documentation separately before selecting a current development environment.
Best Value
- 🎧[128G High Capacity Storage]: This MP3 music player supports up to 128GB Micro TF card (128GB memory card included), which can store up to 4000+ songs and books. Greatly satisfy your need to store songs, videos, audiobooks, let you enjoy music all the time. Support MP3, WMA, WAV, APE, FLAC, AAC-LC, M4A, OGG and other music formats.
- 🎧[Wireless Bluetooth 5.3 and Lossless Sound Quality]: This MP3 player is built-in with the latest Bluetooth 5.3 chip, which provides a more stable and fast connection, better compatibility, and easy connection to remote Bluetooth headphones or Bluetooth speakers. In addition, this MP3 music player has a powerful built-in recording function, HIFI-level sound, clear reproduction of the human voice, so that you feel like immersed in the concert scene.
- 🎧[Multi-functional MP3 Player]: This portable MP3 player is not only a music player, but also a collection of many practical functions, the internal compact body can also play video and pictures, support for one-touch recording, FM radio, reading e-books (TXT format only), alarm clock, calendar, folders, built-in speakers, time screen saver and other functions.
- 🎧 [Compact and Portable, Easy to Use]: This MP3 player is lightweight and portable, you can take it with you anywhere. He is also a companion to accompany your sports, you can take the MP3 running, jogging, cycling, climbing, hiking and so on. 2-3 hours fully charged, up to 45 hours playback time via wired earphones, great for a long trip. Simple operation is easy to use even for the elderly and children!
- 🎧[What You Can Get] You can get an MP3 player, a manual, a 128GB storage card, and a pair of headphones. In addition, this portable MP3 player also comes with a one-year warranty service. If you encounter any problems during use, please contact the seller at any time.
Build sequence
This sequence summarizes the original assembly path; it is not an independently hands-on verified procedure.
- Obtain a Spresense main board and extension board, and identify a compatible four-digit display and the specified button and resistor components.
- Install the historically specified Spresense Arduino support and library version 1.1.3 if reproducing the original code. Observe the author’s bootloader warning.
- Prepare the protoboard and fit headers so it mates with the Spresense board. Keep the GPS antenna area clear.
- Wire the display to the listed GPIO pins and build the five-button resistor network to A3, including the diode and pulldown arrangement in the project diagram.
- Add the microphone breakout only if desired; the published player does not record audio.
- Before powering up, inspect solder joints and shorts and verify the display’s 1.8 V compatibility and current requirements.
- Attach the interface shield to the main board and the main board to the extension board.
- Format the microSD card as directed by the original project, copy
BINto the card root, and add contiguous numbered MP3 files. - Upload the code, connect headphones, and test each button individually. Log A3 readings and recalibrate ranges if any command is misread.
- Test track changes and sustained playback; the project reports roughly two seconds to load a track.
Common problems and how to diagnose them
| Symptom | Likely cause and response |
|---|---|
| A button triggers the wrong command | The ADC value falls outside or near a threshold. Log raw A3 readings, add debouncing and stable-read checks, retain deadbands between ranges, and recalibrate for the actual resistor network. Avoid simultaneous presses. Use separate digital inputs if reliability matters more than conserving pins. |
| No track starts | Check that the card is recognized, the BIN directory is at its root, and the requested numbered file exists. Confirm that track_max matches the contiguous files available. |
| Playback tempo sounds wrong | The project author recommends 192 kbps and reported faster tempo with lower-bitrate files. Try a known-good file at the reported setting, then test other encoding options individually. |
| Display stays dark or behaves erratically | Check the GPIO map and soldering, then verify the display’s electrical compatibility. A 5 V display should not be wired directly to the 1.8 V GPIO without appropriate interfacing. |
| Build fails or board will not behave as expected | Compare the installed Spresense library and bootloader with the project’s historical version notes. Current Sony tooling may not match its 2019 setup. |
| Play/stop behaves badly when USB storage code is enabled | The author disabled the mass-storage code after observing an approximately three-second play/stop problem. The original version should not be treated as reliable USB music-transfer support. |
| Track switching feels slow | The author reports about a two-second loading delay. The published project does not describe this as a setting that can simply be eliminated. |
What is worth modernizing?
The original design is a reasonable base for a control panel, talking instrument, annunciator, or interactive-art installation—the author names these as possible applications. Its compact interface and available I/O invite experimentation, but the playback code is demonstration-scale rather than a maintainable media library.
- Scan a directory and validate files instead of relying on contiguous numbered names and a manually set track count.
- Debounce the ADC buttons, average or stabilize readings, and make thresholds configurable.
- Store settings such as volume and last track across restarts.
- Add recording code before treating the microphone as a feature.
- Design a suitable enclosure and a separately engineered battery and charging circuit if portability is a goal; the original specifies USB power but no battery runtime or charging design.
- Consider a different display, metadata, playlist, or file-transfer system only after checking hardware voltage compatibility and writing the required software.
Who should build it?
Build it if the goal is to learn embedded audio, GPIO, ADC resistor ladders, microSD handling, and physical-interface design on a Sony development platform. It is a poor fit if the goal is simply dependable music playback, Bluetooth headphones, streaming, drag-and-drop library management, or a finished battery-powered device. Sony’s current board listings can help establish regional availability, but the original architecture still requires the extension board and a collection of additional parts.
Quick Recap
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