A 4-oscillator wavetable synthesizer module for Eurorack modular synthesizers, built on the Electrosmith Daisy Seed platform. Features four related outputs, SD card-based wavetable loading, and comprehensive CV control.

• 4 Related Wavetable Oscillators with real-time morphing
• SD Card Wavetable Loading - Up to 12 banks × 8 pages of wavetables
• Comprehensive CV Control - V/Oct tracking, FM, sync, and wavetable morphing
• RGB LED Feedback - Visual indication of parameters and states
• Persistent Settings - Calibration data and user preferences stored in flash

• STM32H750IBK6 - ARM Cortex-M7 microcontroller (Daisy Seed)

• MCP3564R - 24-bit Delta-Sigma ADC for CV inputs
• MCP23008 - 8-bit I2C GPIO expander for button inputs
• TLC59116 - 16-channel LED driver for RGB LED control

• External SDRAM - Wavetable storage (via Daisy Seed)
• QSPI Flash - Persistent settings and calibration data

• ARM GCC Toolchain for embedded ARM development
  • Ubuntu/Debian: sudo apt-get install gcc-arm-none-eabi
  • macOS: brew install --cask gcc-arm-embedded
  • Windows: Download from ARM's website
• Make build system
  • Ubuntu/Debian: sudo apt-get install build-essential
  • macOS: Included with Xcode Command Line Tools
  • Windows: Use MinGW or WSL
• Git with submodule support

This project uses git submodules for dependencies. Clone with:

# Clone with submodules
git clone --recursive https://github.com/Ferry-Island-Modular/FourSeas.git
cd FourSeas

# OR if already cloned without --recursive:
git submodule update --init --recursive

Important: This project uses a forked version of libDaisy with FourSeas-specific modifications. The submodules are configured to use the correct repositories automatically.

# Standard build
make

# Build with custom wavetable sample count
make WAVE_SAMPLES=1024

• BOARD_REV - Hardware board revision (3 or 4, default: 4. If you need rev3, you'll already know)
• WAVE_SAMPLES - Samples per wavetable (default: 2048)

Flash the firmware to your Daisy Seed:

make program  # using ST-Link, or...

make program-jlink  # if you have a J-Link

Or use the Daisy Web Programmer for DFU flashing (no debugger required): https://electro-smith.github.io/Programmer/

Organize wavetable files on the SD card as follows:

/
├── 1/
│   ├── 1.wav
│   ├── 2.wav
│   └── ... (up to 8.wav)
├── 2/
│   ├── 1.wav
│   └── ...
└── ... (up to bank 12)

• WAV files containing wavetable data
• Each file: 8 waves × 8 columns of samples
• Default: 2048 samples per wave (configurable at compile time)
• Supports up to 12 banks with 8 pages each

• 5-position rotary switch
• Inverted output on channel A2

• 8-position rotary switch
• Standard output polarity

The FourSeas module includes a comprehensive calibration routine to ensure accurate V/Oct tracking, proper knob scaling, and correct rotary switch thresholds. Calibration data is automatically saved to flash memory.

To enter calibration mode:

1. Hold both OSC MODE buttons (SW_OSC_MODE_1 and SW_OSC_MODE_2) simultaneously
2. Keep holding for 5+ seconds until the LED light show begins
3. All LEDs will flash 3 times to indicate calibration has started

• LED Indicator: All LEDs turn red
• Action Required:
  • Unplug all CV cables
  • Turn all knobs fully counterclockwise (minimum position)
  • Ensure no CV signals are applied
• Purpose: Establishes zero-point offsets for all analog controls
• Next Step: Press OSC SYNC TYPE 2 button when ready

• LED Indicator: All LEDs turn green
• Action Required:
  • Turn knobs fully clockwise (maximum position)
  • Apply maximum CV signals to all CV inputs
• Purpose: Calibrates scaling for coarse tuning and frequency spread controls
• Next Step: Press OSC SYNC TYPE 2 button when ready

• LED Indicator: All LEDs turn blue
• Action Required:
  • Connect a 1.0V DC precision voltage source to the V/OCT input
  • Ensure accurate voltage (use a calibrated multimeter if needed)
• Purpose: Establishes the low reference point for V/Oct tracking
• Next Step: Press OSC SYNC TYPE 2 button when ready

• LED Indicator: All LEDs turn white (fully on)
• Action Required:
  • Change the voltage source to 3.0V DC (still connected to V/OCT input)
  • Ensure accurate voltage measurement
• Purpose: Establishes the high reference point for V/Oct tracking (2 octaves above C1)
• Next Step: Press OSC SYNC TYPE 2 button when ready

• LED Indicator: LEDs turn on individually as each position is calibrated
• Action Required:
  • Rotate the rotary switch through each position
  • Press OSC SYNC TYPE 2 button at each position
  • LEDs will light up sequentially to indicate progress
• Purpose: Calibrates threshold detection for rotary switch positions
• Completion: Process continues until all switch positions are calibrated

• All LEDs turn off
• Calibration data is automatically saved to flash memory
• Module returns to normal operation
• V/Oct tracking, knob scaling, and switch detection are now calibrated

1. Use a precision voltage source for V/Oct calibration steps
2. Allow the module to warm up for 5-10 minutes before calibrating
3. Work in a stable temperature environment
4. Use a quality multimeter to verify your reference voltages
5. Take your time - accuracy in calibration affects long-term performance

• Calibration won't start: Ensure both OSC MODE buttons are held for full 5+ seconds
• Inaccurate V/Oct tracking: Re-run calibration with verified precision voltage sources
• Switch positions not detecting: Ensure rotary switch is moved to distinct positions during step 5

• J-Link debugger support
• SWO output available for printf debugging
• GPIO toggle points for oscilloscope timing analysis

The FourSeas project supports real-time performance profiling using J-Link's SWO (Serial Wire Output) and the Orbuculum toolchain. This workflow enables detailed analysis of CPU usage, function call patterns, and performance bottlenecks.

1. J-Link debugger with SWO support
2. Orbuculum toolchain - Build from source: https://github.com/orbcode/orbuculum
3. ITM-Tools for data processing - Build from source: https://github.com/orbcode/itm-tools
4. ARM GCC toolchain with GDB

/usr/local/bin/JLinkGDBServerCL -singlerun -nogui -if jtag -port 50000 -swoport 50001 -telnetport 50002 -device STM32H750IB

Parameters:

• -singlerun: Terminate after one GDB session
• -nogui: Run without graphical interface
• -if jtag: Use JTAG interface
• -port 50000: GDB server port
• -swoport 50001: SWO data port
• -telnetport 50002: Telnet port
• -device STM32H750IB: Target MCU

arm-none-eabi-gdb build/FourSeas_rev4_2048.elf -x fs_ocd.cfg

The fs_ocd.cfg configuration file:

• Connects to J-Link GDB server on port 2331
• Configures SWO for 480MHz system clock with 100kHz output
• Enables DWT (Data Watchpoint and Trace) for PC sampling
• Sets up ITM (Instrumentation Trace Macrocell) for printf output

In a separate terminal, run the real-time profiler:

../../orbuculum/build/orbtop -e build/FourSeas_rev4_2048.elf -s localhost:2332 -c 25 -E -v3

Parameters:

• -e: ELF file with debug symbols
• -s localhost:2332: SWO data source (orbuculum server)
• -c 25: Update interval in Hz
• -E: Enable PC sampling
• -v3: Verbose output level

For offline analysis, stream SWO data to a file:

nc localhost 2332 > swo_file_Ofast

Convert raw SWO data to human-readable format:

../../itm-tools/target/debug/pcsampl -e build/FourSeas_rev4_2048.elf swo_file_Ofast 2>/dev/null > pcsampl_Ofast.log

The processed pcsampl_*.log files contain:

• Function call frequencies - Which functions consume the most CPU time
• Call stack analysis - Function call patterns and relationships
• Performance hotspots - Areas of code that may need optimization
• Timing statistics - Execution time distributions

1. Build with optimization: Use -O2 or -O3 for realistic performance measurements
2. Warm-up period: Allow the system to stabilize before capturing data
3. Sufficient sample duration: Capture 30+ seconds of data for meaningful statistics
4. Compare configurations: Profile different build configurations to measure optimization impact
5. Focus on audio callback: Pay special attention to AudioCallback function performance

• No SWO data: Verify J-Link connection and SWO pin configuration
• Garbled output: Check SWO clock speed matches system frequency
• Missing symbols: Ensure ELF file includes debug information (-g flag)
• High CPU usage: SWO data collection itself can impact performance

Generated profiling files follow this naming convention:

• swo_file_*: Raw SWO data captures
• pcsampl_*.log: Processed profiling results
• fs_ocd.cfg: GDB configuration for SWO setup

• FourSeasHW - Hardware abstraction layer
• Ui - User interface and parameter management
• WavetableOscillator - Synthesis engine
• Settings/AppState - Persistent storage management

This project includes the following libraries as git submodules:

• libDaisy - Daisy Seed hardware abstraction
  • Uses Ferry-Island-Modular fork with FourSeas-specific modifications
  • Modifications include: I2C4 peripheral fixes, SDRAM timing, audio SAI handling, crash logging
• DaisySP - Digital signal processing library (upstream)
• stmlib - Parameter interpolation and utilities (upstream)
• FatFS - SD card file system support (included via libDaisy)

MIT License - See LICENSE file for details.

FourSeas is built on top of:

• libDaisy (MIT License) - Ferry-Island-Modular fork
• DaisySP (MIT License) - Electrosmith
• stmlib (MIT License) - Mutable Instruments

Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.

• Follow the existing code style (clang-format configuration included)
• Test on hardware before submitting PRs
• Document any new features or changes to existing behavior
• Keep commits focused and atomic