int E1 = 10;  
int M1 = 12;
int E2 = 11;                        
int M2 = 13;                          

void setup()
{
    pinMode(M1, OUTPUT);  
    pinMode(M2, OUTPUT);
}

void loop()
{
    {
        int value;
        for(value = 0 ; value <= 255; value+=5)
        {
            digitalWrite(M1,HIGH);  
            digitalWrite(M2, HIGH);

            analogWrite(E1, value);   //PWM调速
            analogWrite(E2, value);   //PWM调速
            
            delay(30);
        }
    
        delay(1000);
    }

    { 
        int value;
        for(value = 0 ; value <= 255; value+=5)
        {
            digitalWrite(M1,LOW);  
            digitalWrite(M2, LOW);      

            analogWrite(E1, value);   //PWM调速
            analogWrite(E2, value);   //PWM调速
            
            delay(30);
        }
        
        delay(1000);
    }
}