Skip to main content
Version: FILS English

DIY Embedded Music Player

A hardware digital audio player built on STM32 using Rust and internal DAC audio processing.

info

Author: Alexandru Marioara
GitHub Project Link: https://github.com/UPB-PMRust-Students/fils-project-2026-StrumfoAlex

Description​

This project implements a standalone, fully functional digital music player. It reads audio files from a MicroSD card and outputs sound using the microcontroller's internal DAC (Digital-to-Analog Converter) combined with an external PAM8403 analog amplifier. The system features a graphical interface on an OLED display and allows hardware control via a rotary encoder, IR remote, and tactile buttons.

Motivation​

Music is an essential part of my daily life, and listening to it is a habit I enjoy every single day. This inspired me to build a digital music player from scratch, turning an everyday activity into a complex engineering challenge. From a technical standpoint, this project allows me to combine multiple communication protocols (SPI, I2C) and core microcontroller peripherals (Timers, DMA, DAC) into a single, cohesive product. Instead of using off-the-shelf "smart" modules that do the decoding automatically, I want the STM32 to handle the raw data stream and precisely output it through the internal DAC. This forces me to step out of my comfort zone and tackle real-time asynchronous data streaming using Rust's embassy framework.

Architecture​

The system architecture is centralized around the STM32 microcontroller which handles data fetching, UI updates, and audio signal generation.

                    [POWER & DEBUGGING SECTION]

+-----------------------+             +--------------------------+
|       Host PC         |             |       Host PC            |
|    (USB Power 5V)     |             |    (Serial Debugging)    |
+-----------+-----------+             +------------+-------------+
            |                                      ^
            | (5V & 3.3V)                          | [UART / USB]
            v                                      v
+----------------------------------------------------------------+
|                                                                |
|                     NUCLEO STM32U545RE-Q                       |
|                   (Main Microcontroller)                       |
|                                                                |
+-------+---------------+---------------+---------------+--------+
        |               |               |               |
      [SPI]           [I2C]       [GPIO / EXTI]       [DAC]
        |               |               |               |
        v               v               v               v
+---------------+ +-------------+ +-------------+ +--------------+
|               | |             | |             | |              |
| MicroSD Card  | | 0.96" OLED  | | Buttons &   | |   PAM8403    |
| Module        | | Display     | | Rotary Enc. | |  Amplifier   |
|               | |             | |             | |              |
+---------------+ +-------------+ +-------------+ +-------+------+
 (Stores Audio)     (UI/Visuals)  (User Controls)         |
                                                          | [Analog]
                                                          v
                                                  +--------------+
                                                  |              |
                                                  | 52mm 4 Ohm   |
                                                  | 5W Speaker   |
                                                  +--------------+

The system architecture revolves around the STM32U545RE microcontroller:

  1. Input: Data is read asynchronously from the MicroSD card via SPI. User input is captured via a Rotary Encoder, an IR sensor (for remote control), and tactile buttons.
  2. Processing: The STM32 parses the WAV file format and feeds the raw PCM audio data into memory buffers.
  3. Output: The data is pushed via DMA to the internal DAC to generate an analog audio signal. This signal is then boosted by a PAM8403 amplifier to drive the speaker. The UI state (current song, volume) is updated on the I2C OLED display.

Log​

  • Week 1 - 9: Finalized component list, established architecture using the internal DAC to avoid I2S complexity, and set up the documentation website.
  • Week 9 - ...: (soon...)
  • Week ... - ...: (...)

Hardware​

The project uses a mix of digital sensors and analog amplification to achieve audio playback.

Schematics​

(KiCAD schematic here later)

Bill of Materials​

DeviceUsagePrice
STM32 Nucleo-U545REMain microcontroller (Brain)126 RON
PAM8403 AmplifierAmplifies the analog signal from the STM32 DAC~6 RON
52mm 4 Ohm SpeakerAudio output~20 RON
MicroSD Card ModuleSPI storage for music files~5 RON
0.96" OLED DisplayI2C UI Display~17 RON
IR Receiver & RemoteWireless user interface control~7 RON
Rotary Encoder & ButtonsPhysical user interface controls~15 RON

Software​

The project is built entirely in Rust (no_std) utilizing the asynchronous Embassy framework.

LibraryDescriptionUsage
embassy-stm32Hardware Abstraction LayerControls peripherals (SPI, I2C, DAC, DMA, Timers, GPIO)
embedded-sdmmcFAT32 File SystemReading WAV files from the SD Card
ssd1306Display DriverControlling the OLED screen
embedded-graphics2D GraphicsRendering text and the audio visualizer UI
  1. Rust Embassy Documentation