Uploading Custom Firmware

The NeuroPawn Arduino library keeps EEG acquisition, packet generation, and host commands running while your sketch performs its own non-blocking work. The smallest complete firmware is:

#include <NeuroPawn.h>

void setup() {
  neuropawn.setup();
}

void loop() {
  neuropawn.acquire_data();
}

Before Connecting Electrodes

Disconnect all electrodes and accessories while uploading firmware.
Never connect mains-powered or non-isolated equipment while electrodes are in contact with a person.
Use only an ATmega328P Arduino Nano target and keep the serial monitor at 115200 baud.
Read the firmware resource and pin limits before adding peripherals.

Arduino IDE

1. Install the library

In Arduino IDE, install NeuroPawn Knight Board from Library Manager. If you downloaded a release archive instead, choose Sketch > Include Library > Add .ZIP Library and select NeuroPawn-<version>-arduino.zip.

2. Create the sketch

Start with the minimal firmware above. To add application behavior, keep neuropawn.acquire_data() at the start of every loop and schedule work with millis():

#include <NeuroPawn.h>

unsigned long last_update = 0;

void setup() {
  neuropawn.setup(NP_DEFAULT);

  if (NeuroPawnBoard::pin_available(5)) {
    pinMode(5, OUTPUT);
  }
}

void loop() {
  neuropawn.acquire_data();

  if (millis() - last_update >= 250) {
    last_update = millis();
    digitalWrite(5, !digitalRead(5));
  }
}

3. Select and upload

Connect the board directly by USB.
Select Tools > Board > Arduino AVR Boards > Arduino Nano.
Select the ATmega328P processor and the board’s serial port.
Select Sketch > Upload.

After upload, the firmware begins streaming automatically. All EEG channels are powered down after setup(); activate the required channels from the host with the chon_<channel>_<gain> commands.

PlatformIO

Create a PlatformIO Arduino project with this platformio.ini:

[env:nanoatmega328]
platform = atmelavr
board = nanoatmega328
framework = arduino
monitor_speed = 115200

lib_deps =
    neuropawn/NeuroPawn@^1.0.0

Put the minimal firmware in src/main.cpp, then run PlatformIO: Upload or:

pio run --target upload

Build Firmware With IMU Data

IMU support is a build-time option. It adds about 13 kB of flash use and 640 bytes of RAM use, even before NP_IMU is selected at runtime.

PlatformIO IMU build

Add NEUROPAWN_IMU to the build flags and start the library in NP_IMU mode:

[env:nanoatmega328_imu]
platform = atmelavr
board = nanoatmega328
framework = arduino
monitor_speed = 115200
build_flags = -DNEUROPAWN_IMU

lib_deps =
    neuropawn/NeuroPawn@^1.0.0

#include <NeuroPawn.h>

void setup() {
  neuropawn.setup(NP_IMU);
}

void loop() {
  neuropawn.acquire_data();
}

Arduino IDE IMU build

Arduino IDE does not expose project build flags. In the installed library folder, usually Documents/Arduino/libraries/NeuroPawn_Knight_Board/:

Open src/NeuroPawn.h and uncomment #define NEUROPAWN_IMU near the top.
In library.properties, change the linker setting to ldflags=-lNeuroPawn_imu.
Restart Arduino IDE, then compile a sketch that calls neuropawn.setup(NP_IMU).

To return to an EEG-only build, comment out the define and restore ldflags=-lNeuroPawn.

Rules for Application Code

Call acquire_data() on every loop iteration. At 125 samples per second, blocking for roughly 8 ms can miss a sample.
Do not call delay() or perform long blocking reads. Use millis()-based scheduling and short state machines.
Never call Serial.print() or write unrelated bytes to Serial; it is the binary data link.
Use only pins reported as available by NeuroPawnBoard::pin_available(pin).
Keep interrupt service routines short.

Use neuropawn.quiet(true) before setup() when a host parser must receive only binary data. See Knight Board Firmware for the API, modes, status helpers, and complete hardware limits.