Claw machine controller on an Arduino Uno

// Claw machine controller: the working control electronics inside the cabinet.
//
// Drag the joystick to move the X and Y gantry motors. Press the blue arcade
// button, or press the joystick itself, to run one complete grab cycle:
// lower the winch, close the claw, lift, then release. The cabinet shows the
// claw doing it while Serial names each state. This controller lets go where
// it lifted; the arcade claw machine carries the prize home to the chute.

const int DROP_BUTTON = 2;

const int X_ENABLE = 3;
const int X_A = 4;
const int X_B = 5;
const int Y_ENABLE = 6;
const int Y_A = 7;
const int Y_B = 8;
const int Z_ENABLE = 9;
const int Z_A = 10;
const int Z_B = 11;
const int CLAW_SERVO = 12;

const int JOYSTICK_X = A0;
const int JOYSTICK_Y = A1;
const int DEAD_ZONE = 140;

enum GrabState { READY, LOWERING, CLOSING, LIFTING, RELEASING };
GrabState state = READY;
unsigned long stateStarted = 0;
unsigned long lastServoFrame = 0;
int clawAngle = 35;

void motor(int enable, int a, int b, int speed) {
  if (speed > 0) {
    digitalWrite(a, HIGH);
    digitalWrite(b, LOW);
    analogWrite(enable, speed);
  } else if (speed < 0) {
    digitalWrite(a, LOW);
    digitalWrite(b, HIGH);
    analogWrite(enable, -speed);
  } else {
    analogWrite(enable, 0);
    digitalWrite(a, LOW);
    digitalWrite(b, LOW);
  }
}

int axisSpeed(int reading) {
  int offset = reading - 512;
  if (offset > -DEAD_ZONE && offset < DEAD_ZONE) return 0;
  int magnitude = offset < 0 ? -offset : offset;
  int speed = map(magnitude, DEAD_ZONE, 512, 90, 255);
  if (speed > 255) speed = 255;
  return offset < 0 ? -speed : speed;
}

void servoFrame() {
  unsigned long now = micros();
  if (now - lastServoFrame < 20000) return;
  lastServoFrame = now;
  int pulse = map(clawAngle, 0, 180, 544, 2400);
  digitalWrite(CLAW_SERVO, HIGH);
  delayMicroseconds(pulse);
  digitalWrite(CLAW_SERVO, LOW);
}

void enter(GrabState next, const char *message) {
  state = next;
  stateStarted = millis();
  Serial.println(message);
}

void setup() {
  pinMode(DROP_BUTTON, INPUT_PULLUP);
  for (int pin = X_ENABLE; pin <= CLAW_SERVO; pin++) pinMode(pin, OUTPUT);
  motor(X_ENABLE, X_A, X_B, 0);
  motor(Y_ENABLE, Y_A, Y_B, 0);
  motor(Z_ENABLE, Z_A, Z_B, 0);
  Serial.begin(115200);
  Serial.println("Claw ready: move the stick, then press Drop");
}

void loop() {
  servoFrame();
  unsigned long elapsed = millis() - stateStarted;

  if (state == READY) {
    motor(X_ENABLE, X_A, X_B, axisSpeed(analogRead(JOYSTICK_X)));
    motor(Y_ENABLE, Y_A, Y_B, axisSpeed(analogRead(JOYSTICK_Y)));
    motor(Z_ENABLE, Z_A, Z_B, 0);
    clawAngle = 35;
    if (digitalRead(DROP_BUTTON) == LOW) {
      motor(X_ENABLE, X_A, X_B, 0);
      motor(Y_ENABLE, Y_A, Y_B, 0);
      enter(LOWERING, "1/4 lowering claw");
    }
  } else if (state == LOWERING) {
    motor(Z_ENABLE, Z_A, Z_B, 210);
    if (elapsed >= 1400) {
      motor(Z_ENABLE, Z_A, Z_B, 0);
      clawAngle = 135;
      enter(CLOSING, "2/4 claw closed");
    }
  } else if (state == CLOSING) {
    if (elapsed >= 700) enter(LIFTING, "3/4 lifting prize");
  } else if (state == LIFTING) {
    motor(Z_ENABLE, Z_A, Z_B, -210);
    if (elapsed >= 1400) {
      motor(Z_ENABLE, Z_A, Z_B, 0);
      clawAngle = 35;
      enter(RELEASING, "4/4 prize released");
    }
  } else if (elapsed >= 800 && digitalRead(DROP_BUTTON) == HIGH) {
    enter(READY, "Claw ready");
  }
}