M5Cardputer MP3 Player — EQ Fork

A fully featured, standalone MP3 player for the M5Stack Cardputer, forked from sanchitminda/MP3PlayerForM5Cardputer.

This fork adds a 7-band software equalizer with real-time DSP applied to every audio sample.

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What's new in this fork

7-Band Equalizer

Press E from the player screen to open the EQ:

┌──────────────────────────────────────┐
│             EQUALIZER        [ON]    │
│  60Hz [====|====]  0dB  <- selected │
│ 170Hz [====|====]  0dB              │
│ 310Hz [========|]  +5dB             │
│ 600Hz [====|====]  0dB              │
│  3kHz [====|====]  0dB              │
│  6kHz [==|======] -3dB              │
│ 12kHz [====|====]  0dB              │
│  ;/.:band   ,//:dB   R:reset  `:exit│
└──────────────────────────────────────┘

Band	Type	Frequency
Band 1	Low Shelf	60 Hz
Band 2	Peak	170 Hz
Band 3	Peak	310 Hz
Band 4	Peak	600 Hz
Band 5	Peak	3 kHz
Band 6	Peak	6 kHz
Band 7	High Shelf	12 kHz

EQ Controls:

Key	Action
E (player)	Open EQ screen
; / .	Navigate between bands
, / /	-1 dB / +1 dB (range: -12 to +12)
R	Reset all bands to 0 dB
T	Toggle EQ on/off
`	Save and return to player

Settings are persisted to NVS flash and survive reboots.

Implementation: Biquad IIR filters (direct form II transposed) — 5 multiplications per sample per band per channel. At 7 bands, ~70 operations per stereo sample pair, negligible on ESP32-S3 at 240 MHz.

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Original Features

• Split-screen playlist + Now Playing panel
• FFT visualizer (Classic Bars, Waveform, Circular Spikes, OFF)
• MP3, FLAC, AAC, WAV playback
• Shuffle, Loop (All / One / None)
• Fast-forward / rewind seek
• ID3 tag metadata display
• Wi-Fi Web UI (STA client or AP host mode) for streaming/downloading
• Power saver modes (160 MHz / 80 MHz CPU underclock)
• Display sleep timer
• Pocket Mode (Button A click combinations)
• Multi-theme UI (Gunmetal Blue, Cyberpunk, Retro Amber, Hacker Green)
• Folder-based playlist mode
• Song search
• i18n language file support
• Configurable UI font size

Hardware Requirements

• M5Stack Cardputer (ESP32-S3)
• MicroSD card (FAT32)
• Audio files (.mp3, .flac, .aac, .m4a, .wav)

Building with PlatformIO

The platformio.ini and all required configuration are included in the repository.

git clone https://github.com/silasgubi/MP3PlayerForM5CardputerEQ.git
cd MP3PlayerForM5CardputerEQ
pio run
# Binary: .pio/build/m5stack-cardputer/firmware.bin

The ESP8266Audio library is bundled in lib/ESP8266Audio/. The custom board definition is in boards/m5stack-cardputer.json.

Libraries

Library	Source
M5Cardputer	M5Stack
M5Unified	M5Stack
ESP8266Audio	Bundled in lib/ (Earle F. Philhower, III)

Full Controls

Key	Function
Enter	Play / Pause selected
; / .	Scroll playlist up / down
[ / ]	Volume - / +
N / B	Next / Previous song
/ / ,	Seek forward / backward
S	Toggle Search
F	Toggle Shuffle
L	Toggle Loop (All / One / None)
V	Toggle Visualizer
E	Open Equalizer
`	Open Settings
I	Open Help

Pocket Mode (Button A)

• 1 click: Play/Pause
• 2 clicks: Next
• 3 clicks: Previous

License

Open source. Original work by Sanchit Minda. EQ fork by silasgubi.