IBT-2 BTS7960 big motor driver on an Arduino Uno

// A big brushed motor on an IBT-2 (two BTS7960 half bridges), from an Uno.
//
//   IBT-2 RPWM -> pin 5    LPWM -> pin 6    R_EN, L_EN -> pin 7
//   IBT-2 VCC -> 5V        GND -> GND
//   IBT-2 B+ / B- -> a 12 V battery,  M+ / M- -> the motor
//
// Each half bridge runs while its EN pin is high: RPWM drives M+, LPWM drives
// M-. PWM on one side with the other side low runs the motor one way; swap
// them for the other. Both low brakes, and the enables low let it coast.
// The IBT-2's inputs go through a 74HC244 on 5 V, so they want 5 V logic.

const int RPWM = 5;
const int LPWM = 6;
const int EN = 7;

void drive(int speed) {
  // speed from -255 (full reverse) to 255 (full forward)
  if (speed >= 0) {
    analogWrite(LPWM, 0);
    analogWrite(RPWM, speed);
  } else {
    analogWrite(RPWM, 0);
    analogWrite(LPWM, -speed);
  }
}

void setup() {
  pinMode(EN, OUTPUT);
  digitalWrite(EN, HIGH);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: IBT-2 ramps the motor forward, then back");
}

void loop() {
  for (int s = 0; s <= 255; s += 51) {
    drive(s);
    Serial.print("forward ");
    Serial.println(s);
    delay(400);
  }
  drive(0);
  delay(500);
  for (int s = 0; s <= 255; s += 51) {
    drive(-s);
    Serial.print("reverse ");
    Serial.println(s);
    delay(400);
  }
  digitalWrite(EN, LOW);
  Serial.println("coast");
  delay(1000);
  digitalWrite(EN, HIGH);
}