Mixing 2 channels from an RC hobby controller for arcade drive

two_channel_receiver.ino

/**
 * Two Channel Receiver
 * Author: Shawn Hymel (SparkFun Electronics)
 * Date: Aug 24, 2017
 * 
 * Connect a TB6612FNG and RC (PWM) receiver to the Arduino.
 * Mixes two channels for arcade drive.
 * 
 * This code is beerware; if you see me (or any other SparkFun 
 * employee) at the local, and you've found our code helpful, 
 * please buy us a round! 
 * Distributed as-is; no warranty is given.
 */

// Controller pins
const int CH_1_PIN = 10;
const int CH_2_PIN = 11;

// Motor driver pins
const int STBY_PIN = 9;
const int AIN1_PIN = 2;
const int AIN2_PIN = 4;
const int APWM_PIN = 5;
const int BIN1_PIN = 7;
const int BIN2_PIN = 8;
const int BPWM_PIN = 6;

// Parameters
const int deadzone = 20;  // Anything between -20 and 20 is stop

void setup() {

  // Configure pins
  pinMode(STBY_PIN, OUTPUT);
  pinMode(AIN1_PIN, OUTPUT);
  pinMode(AIN2_PIN, OUTPUT);
  pinMode(APWM_PIN, OUTPUT);
  pinMode(BIN1_PIN, OUTPUT);
  pinMode(BIN2_PIN, OUTPUT);
  pinMode(BPWM_PIN, OUTPUT);

  // Enable motor driver
  digitalWrite(STBY_PIN, HIGH);
}

void loop() {

  // Read pulse width from receiver
  int y = pulseIn(CH_2_PIN, HIGH, 25000);
  int x = pulseIn(CH_1_PIN, HIGH, 25000);

  // Convert to PWM value (-255 to 255)
  y = pulseToPWM(y);
  x = pulseToPWM(x);

  // Mix for arcade drive
  int left = y + x;
  int right = y - x;

  // Drive motor
  drive(left, right);

  delay(5);
}

// Positive for forward, negative for reverse
void drive(int speed_a, int speed_b) {

  // Limit speed between -255 and 255
  speed_a = constrain(speed_a, -255, 255);
  speed_b = constrain(speed_b, -255, 255);

  // Set direction for motor A
  if ( speed_a == 0 ) {
    digitalWrite(AIN1_PIN, LOW);
    digitalWrite(AIN2_PIN, LOW);
  } else if ( speed_a > 0 ) {
    digitalWrite(AIN1_PIN, HIGH);
    digitalWrite(AIN2_PIN, LOW);
  } else {
    digitalWrite(AIN1_PIN, LOW);
    digitalWrite(AIN2_PIN, HIGH);
  }

  // Set direction for motor B
  if ( speed_b == 0 ) {
    digitalWrite(BIN1_PIN, LOW);
    digitalWrite(BIN2_PIN, LOW);
  } else if ( speed_b > 0 ) {
    digitalWrite(BIN1_PIN, HIGH);
    digitalWrite(BIN2_PIN, LOW);
  } else {
    digitalWrite(BIN1_PIN, LOW);
    digitalWrite(BIN2_PIN, HIGH);
  }

  // Set speed
  analogWrite(APWM_PIN, abs(speed_a));
  analogWrite(BPWM_PIN, abs(speed_b));
}

// Convert RC pulse value to motor PWM value
int pulseToPWM(int pulse) {
  
  // If we're receiving numbers, convert them to motor PWM
  if ( pulse > 1000 ) {
    pulse = map(pulse, 1000, 2000, -500, 500);
    pulse = constrain(pulse, -255, 255);
  } else {
    pulse = 0;
  }

  // Anything in deadzone should stop the motor
  if ( abs(pulse) <= deadzone ) {
    pulse = 0;
  }

  return pulse;
}

For anyone having an issue with only one channel working I have a solution. Add a delay(5); between reading the first and second channel. I think I have a delay(5); after the two pulsein() and the drive() and its working pretty sweet.

pls send the code for arduino uno also

Shawn/anyone: Why the map from -500 to 500? Why not map -255-255? It seems that you'd only get half the range of the joystick in response. Half of the PWM input range would always map above 255 and get truncated by constrain. Grateful to understand what I'm misunderstanding here.
re:
pulse = map(pulse, 1000, 2000, -500, 500);
pulse = constrain(pulse, -255, 255);