Teensy 4.0 MP3 Player

Features

• Supported audio codec
  • MP3: 16bit / 44.1KHz, 48KHz
  • AAC: 16bit / 44.1KHz, 48KHz
  • WAV: 16bit, 24bit / 44.1KHz, 48KHz, 88.2KHz, 96KHz, 176.4KHz, 192KHz
  • FLAC: 16bit, 24bit / 44.1KHz, 48KHz, 88.2KHz, 96KHz, 176.4KHz, 192KHz
• Supported tag
  • ID3/ID3v2.2/ID3v2.3/ID3v2.4 tag for MP3, WAV
  • MP4 tag for AAC (m4a)
  • LIST chunk for WAV
  • FLAC tag (Vorbis comment) for FLAC
  • JPEG, PNG Cover Art embedded in Tag (multiple images supported)
• Audio output to I2S DAC and/or S/PDIF (Toslink)
• exFAT format microSD by SDIO (confirmed up to 1TB UHS-I Speed Class 3 card)
• Sorted folder/File navigation by UTF16 with unicode font
• User Interface by Android Headphone button (3 buttons)
• Volume Control by utilizing DAC 24bit/32bit range for playing 16bit Audio data
• Album unit Sequential/Repeat/Random play by time out when play finished (Assuming [Artist Folder]/[Album Folder] structure)
• Resume playback
• Battery voltage check (Optional: external circuit needed)

Note

• Progressive JPEG Cover Art not supported
• Fast Forward / Fast Rewind not supported
• Gapless playback not supported

Supported Board and Peripheral Devices

Main board

• Teensy 4.0

LCD module

• ST7789 1.3" LCD (240x240 pix) without CS type
• IL9341 2.2" LCD (240x320 pix)
• ST7735 1.8" LCD (128x160 pix)

I2S DAC

• ES9023 24bit I2S Audio DAC
• PCM5102 32bit I2S Audio DAC

S/PDIF Tx (Optional)

• DLT1160A-T-1 (or equivalent module)

Pin Assignment

In addition to original connection

Teensy4.0 Pin	Function	Connection
2	OUT2	to S/PDIF Tx
3	GPIO	to S/PDIF Power
6	GPIO	to ES9023 MUTE_B (15) / to PCM5102 XSMT (17)
7	OUT1A	to ES9023 SDI (3) / to PCM5102 DIN (14)
8	GPIO	to LCD DC
9	GPIO	to LCD RST
10	CS	to LCD CS
11	MOSI	to LCD MOSI
13	SCK	to LCD SCK
14	A0	from Battery Voltage
15	GPIO	to LCD Backlight control (Optional)
16	GPIO	to Power Keep (DC/DC)
18	GPIO	to Battery Check
20	LRCLK1	to ES9023 LRCK (2) / to PCM5102 LRCK (15)
21	BCLK1	to ES9024 BCK (1) / to PCM5102 BCK (13)
22	A8	from Android Head Phone MIC (Button)
23	MCLK	to ES9023 MCLK (13)
34	DAT1	from/to microSD DAT1
35	DAT0	from/to microSD DAT0
36	CLK	to microSD CLK
37	CMD	from/to microSD CMD
38	DAT3	from/to microSD DAT3
39	DAT2	from/to microSD DAT3

tie PCM5102 SCK (12) to low

Schematic

Teensy40_MP3_Player_schematic.pdf

I2S DAC

Both ES9023 and PCM5102 are supported without code definition change.

PCM5102 Board Setting

• tie PCM5102 SCK (12) to low
• open H3L

LCD Module

• ST7735 1.8" LCD (128x160 pix)

* ST7789 1.3" LCD (240x240 pix) without CS type

* IL9341 2.2" LCD (240x320 pix)

microSD

Drive strength configuration for SDIO

Please set SDIO_CTL_PAD_DSE_VAL in platformio.ini depending by microSD Card connection condition.

• Direct Connection on Teensy 4.0 Board such as Hinged type microSD connector: SDIO_CTL_PAD_DSE_VAL = 1
• Connect through Flexible cable less than 5cm: SDIO_CTL_PAD_DSE_VAL = 1~2
• With longer cable and/or more load than above cases: SDIO_CTL_PAD_DSE_VAL = 2~4

It is recommended to check microSD access stability in advance by SdInfo and bench projects with Arduino environment.

Confirmed microSD Cards

• SanDisk microSDXC Ultra A1 64GB (UHS-I Speed-class 1)
• SanDisk microSDXC Ultra A1 512GB (UHS-I Speed-class 1)
• SanDisk microSDXC Extreme A2 1TB (UHS-I Speed-class 3)

Unicode Font File

Place resource/unifont.bin on microSD root folder

How to build

Build using Docker image (recommended):

docker run --rm -v $(pwd):/project -w /project elehobica/teensy40-docker:1.0.0 pio run -e ST7789_240x240

Select your LCD type by specifying the PlatformIO environment variable with -e:

Environment	LCD Module
ST7735_128x160	1.8" ST7735 128x160
ST7789_240x240	1.3" ST7789 240x240
ILI9341_240x320	2.2" ILI9341 240x320

Alternatively, install Visual Studio Code with the PlatformIO IDE extension and select the environment from the status bar.

How to upload firmware

You can upload a pre-built firmware.hex (e.g. from Releases or CI artifacts) using Teensy Loader CLI.

teensy_loader_cli --mcu=TEENSY40 -wvs firmware-xxx.hex

• Press the button on Teensy 4.0 board to enter bootloader mode before running the command, or use -s option to wait for a soft reboot
• Teensy Loader CLI is also bundled in PlatformIO package at ~/.platformio/packages/tool-teensy/teensy_loader_cli
• Alternatively, Teensy Loader (GUI application) can be used to open and upload .hex files

Button Control Guide

Connect MIC pin of Android headphone remote control with 3 buttons to A8 pin of Teensy 4.0. A8 also needs to be pulled-up by 2.2Kohm from 3.3V. See schematic for detail.

FileView Mode

• Up/Down button to go up/down for file selection
• Center 1 click to get into the folder
• Center 1 click to play WAV file (go to Play Mode)
• Center 2 clicks to go parent folder
• Center 3 clicks to Random album play (go to Play Mode)
• Long push Center button to go to Config Mode
• 1 min passed without any button: Sequential/SequentialRepeat/Repeat/Random album play (go to Play Mode)

Play Mode

• Up/Down button for volume up/down
• Center 1 click to pause/play
• Center 2 clicks to stop (go back to FileView Mode)
• Center 3 clicks to Random album play
• Long push Center button to go to Config Mode

Config Mode

• Up/Down button to go up/down to select config items
• Center 1 click to determine config values
• Center 2 clicks to go back to previous Mode (FileView or Play)
• Long push to Power Off (Optional: external circuit needed)

Power On (Optional: external circuit needed)

• Long push Center button

Prototype Example

• with ST7789_240x240_WOCS and ES9023

• with ILI9341_240x320 and ES9023

• with ST7735_128x160 and ES9023

• with ST7735_128x160 and PCM5102