NAMPedal

A guitar amp modeler pedal for the Daisy Pod running Neural Amp Modeler (NAM) models. It loads .namb binary model files from an SD card and provides two knobs for gain (input level) and volume (output level).

Motivation

This was created as a helpful blueprint to guide the creation of embedded devices that can run NAM. For more information on the work that led to this, check this blog post.

Prerequisites

• DaisyToolchain — ARM cross-compiler and tools for the Daisy platform
• A Daisy Pod board with a micro SD card
• A USB cable and serial terminal application (see note above)

Important — USB serial terminal required: The firmware currently waits for a USB serial connection at startup (StartLog(true)). If no serial terminal is connected, the board will stall indefinitely and never reach the audio engine. You must open a serial terminal (e.g. screen, minicom, PuTTY, or the Arduino Serial Monitor) on the Daisy's USB port before powering on / resetting the board. See the Serial Monitor section for details.

Setup

1. Clone DaisyExamples and build libDaisy

git clone https://github.com/electro-smith/DaisyExamples
cd DaisyExamples
git submodule update --init --recursive
cd libDaisy
make
cd ..

2. Clone NAMPedal

cd seed
git clone --recursive https://github.com/tone-3000/NAMPedal
cd NAMPedal

The --recursive flag pulls in the two submodules:

• NeuralAmpModelerCore — DSP engine (LSTM, WaveNet, ConvNet architectures)
• nam-binary-loader — .namb binary model parser

Building

make

This cross-compiles for the STM32H750 (Cortex-M7) using BOOT_QSPI app type for the larger binary size NAM requires.

Flashing

Because this app leverages Daisy's QSPI flash memory to accommodate program size, a bootloader must be flashed before the main program.

To install a bootloader, put the Daisy Pod into DFU mode (hold BOOT, press RESET), then:

make program-boot

When the Daisy power-cycles (can trigger manually by pressing RESET), you will see the BOOT led sweep in and out, indicating a grace period during which the device can be flashed by running:

make program-dfu

The grace period can be extended indefinitely by pressing BOOT.

Usage

Serial Monitor

The firmware calls StartLog(true) at boot, which blocks until a USB serial terminal is connected. If you power on the board without a serial terminal attached, it will appear to do nothing — it is waiting for the USB connection.

Before powering on or resetting the board, open a serial terminal on the Daisy's USB serial port using one of the methods below.

macOS

The Daisy shows up as /dev/cu.usbmodem*. Find the exact name and connect:

ls /dev/cu.usbmodem*
screen /dev/cu.usbmodem12345 115200

To exit screen, press Ctrl-A then K and confirm with y.

Alternatively, if you have Homebrew you can install minicom:

brew install minicom
minicom -D /dev/cu.usbmodem12345 -b 115200

Linux

The Daisy shows up as /dev/ttyACM*. You may need to add your user to the dialout group for access (log out and back in after):

sudo usermod -aG dialout $USER

Then find the port and connect:

ls /dev/ttyACM*
screen /dev/ttyACM0 115200

Or using minicom:

sudo apt install minicom          # Debian / Ubuntu
minicom -D /dev/ttyACM0 -b 115200

Windows

1. Find the COM port: Open Device Manager and expand Ports (COM & LPT). The Daisy will appear as a USB Serial Device (e.g. COM3).

2. Connect with PuTTY:

   • Download PuTTY
   • Set Connection type to Serial
   • Enter the COM port (e.g. COM3) and speed 115200
   • Click Open

3. Or use the Arduino IDE: Open the Serial Monitor (Tools > Serial Monitor), select the correct port, and set the baud rate to 115200.

4. Or use PowerShell (no extra software needed):

   # Replace COM3 with your port
   $port = New-Object System.IO.Ports.SerialPort COM3,115200
   $port.Open()
   while ($true) { if ($port.BytesToRead) { $port.ReadExisting() | Write-Host -NoNewline } }

Once the serial terminal is connected you will see boot messages, model loading status, a one-shot benchmark, and a once-per-second diagnostics line:

NAMPedal: booting...
FS mount: OK
Loading model: nano_relu.namb
  file size: 1756 bytes
  read OK (1756 bytes)
  model ready (12 ms)
Benchmark: 142350 cycles for 48 frames (budget=480000)
  0.30 ms (deadline 1.00 ms)
Audio engine started
cb=48  cycles=142200  max=142350  gain=0.500  vol=0.750  BYPASS

Getting a NAM Model

The firmware loads a .namb (binary) model file from the SD card. Most NAM models are distributed as .nam (JSON) files, so you need to convert them first.

1. Download a model

Download the nano relu version of the Fender '65 Deluxe Reverb Boosted with Klon model from Tone3000. The nano relu architecture is small enough to fit within the 4 KB model buffer and fast enough to run in real time on the Daisy.

Note: Only nano (and some feather) models are small and fast enough for the Daisy's Cortex-M7. Larger architectures (standard, lite) will either exceed the file size limit or miss the 1 ms audio deadline.

2. Convert .nam to .namb

The nam-binary-loader submodule includes a converter tool. Build it from the repository root:

cd nam-binary-loader
mkdir build && cd build
cmake .. -DNAM_CORE_PATH=../../NeuralAmpModelerCore
make

Then convert your downloaded model:

./nam2namb /path/to/downloaded-model.nam nano_relu.namb

3. Copy to SD card

Copy the resulting nano_relu.namb file to the root of a FAT32-formatted micro SD card.

Running the Pedal

1. Insert the SD card (with nano_relu.namb at the root) into the Daisy Pod
2. Connect the Daisy Pod to your computer via USB and open a serial terminal (see above)
3. Power on or reset the board — the serial terminal must be open before this step
4. Wait for the Audio engine started message in the serial output
5. Connect your guitar to the audio input and an amp/headphones to the audio output

Controls

Control	Function
KNOB 1	Gain (input level)
KNOB 2	Volume (output level)
Button 1	Toggle bypass (red LED = bypass, green LED = active)

LED Indicator

• Red — Effect is bypassed (clean passthrough)
• Green — Effect is active (NAM model processing)

Troubleshooting

Symptom	Cause	Fix
Board appears dead after flashing	No serial terminal connected; firmware is waiting for USB	Connect a serial terminal, then reset the board
FS mount: FAILED in serial output	SD card not inserted, not FAT32, or bad contact	Re-format the SD card as FAT32 and re-insert
f_open failed	Model file missing or wrong filename	Ensure the file is named nano_relu.namb at the root of the SD card
file too large	Model exceeds the 4 KB buffer	Use a smaller model (e.g. a nano or feather variant exported with NAM)
Audio glitches / dropouts	Model inference exceeds the 1 ms per-block deadline	Use a smaller/simpler model architecture; check the benchmark output

How it Works

• Audio is processed mono — the left input channel is fed through the NAM model and the output is duplicated to both stereo channels
• The model is loaded once at startup from the SD card into RAM, then prewarm() is called to stabilize initial state
• NAM_SAMPLE is defined as float (via NAM_SAMPLE_FLOAT) to match Daisy's audio buffers and halve memory usage compared to double precision
• The audio block size is 48 samples at 48 kHz, giving a 1 ms processing deadline per block
• FPU Flush-to-Zero and Default-NaN modes are enabled to avoid costly denormal handling on the Cortex-M7