Cassette Flow Firmware

This project is a custom firmware for ESP32-based audio boards, originally designed for the ESP32-LyraT v4.3 and ported to the Ai-Thinker ESP32-A1S-AudioKit.

Supported Boards

• Ai-Thinker ESP32-A1S-AudioKit (ES8388 Codec Version) - Default Configuration
• ESP32-LyraT v4.3

Building for Ai-Thinker ESP32-A1S-AudioKit

The project is currently configured by default for the Ai-Thinker board using a custom component in components/audio_board.

Prerequisites

• ESP-IDF v4.3+ (v4.3.2 is verified)
• ESP-ADF

Build Steps

1. Navigate to the project directory.
2. Clean the build (optional but recommended):

   idf.py fullclean

3. Build the project:

   idf.py build

4. Flash and Monitor:

   idf.py -p <PORT> flash monitor

Key Board Modifications

• MCLK Generation: MCLK is force-enabled on GPIO 0 within board.c initializtion to support the ES8388 codec.
• SD Card: Configured for 1-Line mode (SD_MODE_1_LINE) to match the hardware connections.
• LEDs: The standard display service for LEDs is stubbed out as this board uses simple GPIOs.

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Building for ESP32-LyraT v4.3

To target the original LyraT board, you must disable the custom board component and revert to the standard ADF definition.

Steps to Switch

1. Disable Custom Component: Rename or remove the local components/audio_board directory so the build system doesn't find it.

   mv components/audio_board components/audio_board_disabled

2. Configure Menuconfig:
   • Run idf.py menuconfig
   • Go to Audio HAL > Audio Board
   • Select ESP32-LyraT V4.3
   • Save and Exit.
3. Clean and Build:

   idf.py fullclean
   idf.py build

Troubleshooting

• No Audio (Ai-Thinker): Ensure GPIO 0 is not being used by other peripherals, as it is required for the MCLK signal to the codec.
• SD Card Mount Failed: Ensure the card is formatted FAT32. The A1S board only supports 1-Line mode securely on most revisions.

Hardware Buttons

The buttons on the Ai-Thinker AudioKit are mapped as follows:

Button	Label on Board	Function
REC	KEY1 (GPIO 36)	Select Side A (Switch pipeline to use Side A tape file)
MODE	KEY2 (GPIO 13)	Select Side B (Switch pipeline to use Side B tape file)
PLAY	KEY3 (GPIO 19)	Play / Passthrough Toggle - In Decode/Play mode: Switch to Passthrough (Live Input) - In Passthrough: Switch back to Playback - In Encode mode: Start/Stop Recording
SET	KEY4 (GPIO 23)	EQ Toggle (Cycle Equalizer presets)
VOL+	KEY5 (GPIO 18)	Volume Up
VOL-	KEY6 (GPIO 5)	Volume Down

WiFi Configuration

The device connects to WiFi using credentials loaded from the SD card.

1. Create a file named wifi_config.txt in the root of your SD card.
2. Add your SSID and Password separated by a tab character.

   YourSSID	YourPassword
   

3. If this file is missing, the firmware uses fallback credentials.

To set your own default credentials (if you prefer not to use the SD card), edit main/config.h and recompile:

#define CONFIG_WIFI_SSID "YourSSID"
#define CONFIG_WIFI_PASSWORD "YourPassword"

To access the web interface or API, find the IP address via the serial monitor (idf.py monitor).

Web API Reference

The board runs an HTTP server on port 80.

URI	Method	Description	Parameters
/	GET	Set operation mode	mode: encode, decode, or pass
/play	GET	Start playback	side: a or b
/stop	GET	Stop pipeline	None
/vol	GET	Set volume	value: 0-100
/output	GET	Set audio output	device: SP (Speaker) or BT (Bluetooth) Optional btdevice: Name of BT device
/eq	GET	Set Equalizer	band: comma-separated list of 10 integer values
/mp3db	GET	List MP3 database	None
/tapedb	GET	List Tape database	None
/info	GET	Get status info	None
/raw	GET	Stream raw data	None
/dct	GET	Enable DCT mapping	Optional offset: integer seconds
/create	GET	Create tape config	side (a/b), tape (length), mute, data
/start	GET	Start encoding	side: a or b

Examples

General Control

• Set Mode to Encode: http://<IP>/?mode=encode
• Set Mode to Decode (Play): http://<IP>/?mode=decode
• Set Mode to Passthrough: http://<IP>/?mode=pass
• Stop All Operations: http://<IP>/stop
• Get System Info: http://<IP>/info
• Set Volume to 80%: http://<IP>/vol?value=80

Playback

• Play Side A: http://<IP>/play?side=a
• Play Side B: http://<IP>/play?side=b
• Switch Output to Bluetooth: http://<IP>/output?device=BT&btdevice=MySpeaker
• Switch Output to Speaker: http://<IP>/output?device=SP
• Set Equalizer: http://<IP>/eq?band=-2,0,2,4,2,0,-2,-4,-2,0 (10 bands)

Tape & Database

• List MP3 Database: http://<IP>/mp3db
• List Tape Database: http://<IP>/tapedb
• Create Tape Config: http://<IP>/create?side=a&tape=60&mute=5&data=0001,mp3_1,mp3_2...
• Start Encoding Side A: http://<IP>/start?side=a

Data Streaming

• Stream Raw Line Data: http://<IP>/raw
• Enable DCT Mapping: http://<IP>/dct
• Enable DCT Mapping with Offset: http://<IP>/dct?offset=1800 (Shift mapping by 30 mins)

Monitoring CPU Usage

To view real-time CPU usage statistics per task on the serial monitor:

1. Run idf.py menuconfig.
2. Navigate to Component config -> FreeRTOS.
3. Enable Enable FreeRTOS to collect run time stats.
4. Save and Exit.
5. Rebuild and flash: idf.py build flash monitor.

The console will output a table every second showing task runtimes and CPU percentage.