Parkinson’s Tremor Detection Pen

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

constexpr int I2C_SDA_PIN = 21;
constexpr int I2C_SCL_PIN = 22;
constexpr int START_BUTTON_PIN = 25;
constexpr int MARK_BUTTON_PIN = 26;
constexpr int BUZZER_PIN = 27;
constexpr int FSR_PIN = 34;
constexpr uint8_t OLED_ADDRESS = 0x3C;
constexpr int SCREEN_WIDTH = 128;
constexpr int SCREEN_HEIGHT = 64;
constexpr uint32_t SAMPLE_INTERVAL_MS = 20;
constexpr uint32_t DISPLAY_INTERVAL_MS = 250;
constexpr uint32_t DEBOUNCE_MS = 35;

Adafruit_MPU6050 mpu;
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

bool recording = false;
bool mpuReady = false;
float ax = 0.0f, ay = 0.0f, az = 0.0f, gx = 0.0f, gy = 0.0f, gz = 0.0f;
int fsrRaw = 0;
uint32_t lastSampleMs = 0;
uint32_t lastDisplayMs = 0;
uint32_t sampleNumber = 0;

bool lastStartReading = HIGH;
bool stableStartState = HIGH;
uint32_t startChangedMs = 0;
bool lastMarkReading = HIGH;
bool stableMarkState = HIGH;
uint32_t markChangedMs = 0;

void beep(uint16_t frequency, uint16_t durationMs) {
  ledcWriteTone(BUZZER_PIN, frequency);
  delay(durationMs);
  ledcWriteTone(BUZZER_PIN, 0);
}

void drawStatus() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("Parkinson's pen");
  display.drawLine(0, 10, SCREEN_WIDTH - 1, 10, SSD1306_WHITE);
  display.setCursor(0, 16);
  display.print("MPU: ");
  display.println(mpuReady ? "ready" : "not found");
  display.setCursor(0, 28);
  display.print("Grip: ");
  display.println(fsrRaw);
  display.setCursor(0, 40);
  display.print("USB CNN: JSON lines");
  display.setCursor(0, 52);
  display.print(recording ? "REC  #" : "READY");
  if (recording) display.print(sampleNumber);
  display.display();
}

void sendHeader() {
  Serial.println("{\"type\":\"smart_pen\",\"format\":\"jsonl\",\"sample_hz\":50,\"units\":{\"accel\":\"m_s2\",\"gyro\":\"rad_s\"},\"fields\":[\"t_ms\",\"ax\",\"ay\",\"az\",\"gx\",\"gy\",\"gz\",\"fsr\"]}");
}

void sendSample(uint32_t now) {
  Serial.print("{\"t_ms\":"); Serial.print(now);
  Serial.print(",\"ax\":"); Serial.print(ax, 5);
  Serial.print(",\"ay\":"); Serial.print(ay, 5);
  Serial.print(",\"az\":"); Serial.print(az, 5);
  Serial.print(",\"gx\":"); Serial.print(gx, 5);
  Serial.print(",\"gy\":"); Serial.print(gy, 5);
  Serial.print(",\"gz\":"); Serial.print(gz, 5);
  Serial.print(",\"fsr\":"); Serial.print(fsrRaw);
  Serial.println("}");
}

bool pressedEvent(int pin, bool &lastReading, bool &stableState, uint32_t &changedMs, uint32_t now) {
  const bool reading = digitalRead(pin);
  if (reading != lastReading) changedMs = now;
  if ((now - changedMs) >= DEBOUNCE_MS && reading != stableState) {
    stableState = reading;
    lastReading = reading;
    return stableState == LOW;
  }
  lastReading = reading;
  return false;
}

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  pinMode(START_BUTTON_PIN, INPUT_PULLUP);
  pinMode(MARK_BUTTON_PIN, INPUT_PULLUP);
  ledcAttach(BUZZER_PIN, 2000, 8);
  ledcWriteTone(BUZZER_PIN, 0);

  Wire.begin(I2C_SDA_PIN, I2C_SCL_PIN);
  mpuReady = mpu.begin(0x68, &Wire);
  if (mpuReady) {
    mpu.setAccelerometerRange(MPU6050_RANGE_8_G);
    mpu.setGyroRange(MPU6050_RANGE_500_DEG);
    mpu.setFilterBandwidth(MPU6050_BAND_21_HZ);
  }

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDRESS)) {
    Serial.println("{\"type\":\"error\",\"message\":\"OLED not found at 0x3C\"}");
  }
  if (mpuReady) {
    Serial.println("{\"type\":\"status\",\"message\":\"MPU6050 ready\"}");
    beep(2200, 70);
  } else {
    Serial.println("{\"type\":\"error\",\"message\":\"MPU6050 not found at 0x68\"}");
    beep(450, 250);
  }
  sendHeader();
  drawStatus();
}

void loop() {
  const uint32_t now = millis();
  if (pressedEvent(START_BUTTON_PIN, lastStartReading, stableStartState, startChangedMs, now)) {
    recording = !recording;
    if (recording) {
      sampleNumber = 0;
      Serial.println("{\"type\":\"recording\",\"state\":\"started\"}");
      beep(1800, 70);
    } else {
      Serial.println("{\"type\":\"recording\",\"state\":\"stopped\"}");
      beep(900, 120);
    }
    drawStatus();
  }
  if (pressedEvent(MARK_BUTTON_PIN, lastMarkReading, stableMarkState, markChangedMs, now)) {
    Serial.print("{\"type\":\"event\",\"t_ms\":");
    Serial.print(now);
    Serial.println(",\"name\":\"user_mark\"}");
    beep(2600, 45);
  }
  if (recording && now - lastSampleMs >= SAMPLE_INTERVAL_MS) {
    lastSampleMs = now;
    fsrRaw = analogRead(FSR_PIN);
    if (mpuReady) {
      sensors_event_t acceleration, gyroscope, temperature;
      mpu.getEvent(&acceleration, &gyroscope, &temperature);
      ax = acceleration.acceleration.x;
      ay = acceleration.acceleration.y;
      az = acceleration.acceleration.z;
      gx = gyroscope.gyro.x;
      gy = gyroscope.gyro.y;
      gz = gyroscope.gyro.z;
    } else {
      ax = ay = az = gx = gy = gz = 0.0f;
    }
    sendSample(now);
    ++sampleNumber;
  }
  if (now - lastDisplayMs >= DISPLAY_INTERVAL_MS) {
    lastDisplayMs = now;
    if (!recording) fsrRaw = analogRead(FSR_PIN);
    drawStatus();
  }
}