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@rallard

Try changing the I to i in the for loop.

for ( int i= 255; i >= 0; --i);

C++ is case sensitive and you apparently have not defined i anywhere.
Defining a variable means this,
int i; // define i as an integer
which I am guessing is the case when you set up the for loop with I when you meant i.

Welcome! I hope you enjoy your time here. By way of a tip, when pasting code for feedback / debugging help, a single line is not really sufficient context. There is also a "code" format block (the <> symbol above the text you're writing) that helps with readability - so assuming your code looks something like this:

for( int I=255;  I>=0; --i );
   analogWrite( enA, i);

 There are two issues - the first of which is that you have a mixed case, with the first two parts of the for loop conditions using capital I, and the pre-decrement operator (--i) using lower case. The int statement in the first bit of the for loop declares the I to be in scope for the loop, but not the lower case i.

The second issue is that the for loop ends with a semi-colon in your code, which means that the loop does nothing in it's body - it's a null loop. Stylistically, when writing a null loop, I would format it as such:

for( int i=255; i>=0; --i )
   ;

I recommend a couple different things - first, always declare your variables into existence on a separate line, and always indent your loop body, even if it's a null loop - and even better, always use braces for loop bodies, as it is explicitly clear in that case what is looped.

const int enA = 9; // Analog pin for motor
int i; // Loop index variable

for( i=255; i >=0; --i) {
   analogWrite( enA, i);
}

@rallard

Welcome to the forum 🙂

Besides the obvious error in upper/lower case mentioned, it seems extremely strange that you should be trying to set the enable pin to any value other than 0 (zero) or 1 (one).

This suggests that you have a logic or comprehension problem as well, so feel free to post your code and ask for help if you need more advice.

@will Thank You Will.

I don't think version of windows allows me to run sketches!

I will go over my sketch again to find out what else is wrong.

@binaryrhyme Thank You very much for your advice

@robotbuilder Thank you for your help.

#include <Servo.h>

//L298N Motor Control Demonstration with 2 Potentiometers
// L298N-Motor-Control- Demo-2pots.ino
// Demonstrates use of 2 potentiometer with Arduino and L298N Motor Controller

DroneBot Workshop 2017
http://dronebotworkshop.com
*/

// Motor A

int enA = 9;
int in1 = 8;
int in2 = 7;

// Motor B
int enB = 3;
int in3 = 5;
int in4 = 4;

//Speed control potentiometers

int SpeedControl1 = A0;
int SpeedControl2 = A1;

//Motor Speed Values - Start at zero

int MotorSpeed1 = 0;
int MotorSpeed2 = 0;

void setup()

{
// Set all the motor control pins to outputs
pinMode(enA, OUTPUT);
pinMode(enB, OUTPUT);
pinMode(in1, OUTPUT);
pinMode(in2, OUTPUT);
pinMode(in3, OUTPUT);

}

void loop() {
// Set Motor A Forward

digitalwrite(in1, HIGH);
digitalwrite(in2, LOW);

// Set Motor B Forward

digitalwrite(in3, HIGH);
digitalwrite(in4, LOW);

// Read the values from the potentiometers

MotorSpeed1 = analogRead(SpeedControl1);
MotorSpeed2 = analogRead(speed Control2);

// Convert to renge of 0-255

MotorSpeed1 = map(MotorSpeed, 0,1023, 0, 255;
MotorSpeed2 = map(MotorSpeed, 0,1023, 0, 255;

// Adjust to prevent 'buzzing' at very low speed

if (MotorSpeed1 = 0)MotorSpeed1 = 0;
if (MotorSpeed2 = 0)MotorSpeed2 = 0;

// Set the Motor speeds

analogwrite(enA, Motorspeed1);
analogwrite(enB, Motorspeed2);
}

@robotbuilder 

@robotbuilder

/*
L296N Motor Demonistration
L298N Motor-Demo.inoo
Demonisrtates functions of L298N Motor Controller

DroneBot Workshop 2017
http://dronebotworkshop.com <
*/

// Motor A

int enA = 9;
int in1 = 8;
int in2 = 7;

// Motor B

int enB = 3;
int in3 = 5;
int in4 = 4;

void setup()

{

// Set all the motor control pins to output

pinMode(enA, OUTPUT);
pinMode(enB, OUTPUT);
pinMode(in1, OUTPUT);
pinMode(in2, OUTPUT);
pinMode(in3, OUTPUT);
pinMode(in4, OUTPUT);

}

void demo0ne()

{

// This function will run the motors in both directions at a fixed speed

// turn on motor A

digitalWrite(in1, HIGH);
digitalWrite(in2, LOW);

// Set speed to 200 out of possible range 0-255

analogWrite(enA, 200);

// Turn on motor B

digitalWrite(in3, HIGH);
digitalWrite(in4, LOW);

// Set speed to 200 out of possible range 0-255

analogWrite(enB, 200);

delay(2000);

// Now change motor directions

digitalWrite(in1, LOW);
digitalWrite(in2, HIGH);
digitalWrite(in3, LOW);
digitalWrite(in4, HIGH);

delay(2000);

// Now turn off motors

digitalWrite(in1, LOW);
digitalWrite(in2, LOW);
digitalWrite(in3, LOW);
digitalWrite(in4, LOW);

}
void demoTwo()

{

// This function will run the motors acrossthe range of possible speeds
// Note that maximum speed is determined by the motor itself and the operating voltage

// Turn on motors

digitalWrite(in1, LOW);
digitalWrite(in2, HIGH);
digitalWrite(in3, LOW);
digitalWrite(in4, HIGH);

// Accelerate from zero to maximum speed

for (int i = 0; i = 256; i++)

[

analogWrite(enA, i);
analogWrite(enB, i);

delay(20);

]

// Decelerate motors from maximum speed to zero
for(int i = 255; i >= 0; i--);

[

analogWrite(enA; i);
analogWrite(enB; i);

delay(20);

}

// Now turn off motors

digitalWrite(in1, LOW);
digitalWrite(in2, LOW);
digitalWrite(in3, LOW);
digitalWrite(in4, LOW);

}

void loop()

{

demo0ne()

delay(1000);

demoTwo()

delay(1000);

}

Sorry, binaryrhyme; This is the sketch that would not compile

@rallard Looks like you are missing the includes, let me check.

@rallard There are a number of simple errors that the compiler is pointing out. I fixed those and now it compiles. It almost looks like you have a keyboard issue, or a char-set issue as a few things like {} were displayed as [] and caused an error. If you are unable to fix the errors that the compiler points out let us know, I have a working copy.

@rallard Did you select the UNO board?

@rallard Here is the corrected code

// Motor A

int enA = 9;
int in1 = 8;
int in2 = 7;

// Motor B

int enB = 3;
int in3 = 5;
int in4 = 4;

void setup()

{

// Set all the motor control pins to output

pinMode(enA, OUTPUT);
pinMode(enB, OUTPUT);
pinMode(in1, OUTPUT);
pinMode(in2, OUTPUT);
pinMode(in3, OUTPUT);
pinMode(in4, OUTPUT);

}

void demo0ne()

{

// This function will run the motors in both directions at a fixed speed

// turn on motor A

digitalWrite(in1, HIGH);
digitalWrite(in2, LOW);

// Set speed to 200 out of possible range 0-255

analogWrite(enA, 200);

// Turn on motor B

digitalWrite(in3, HIGH);
digitalWrite(in4, LOW);

// Set speed to 200 out of possible range 0-255

analogWrite(enB, 200);

delay(2000);

// Now change motor directions

digitalWrite(in1, LOW);
digitalWrite(in2, HIGH);
digitalWrite(in3, LOW);
digitalWrite(in4, HIGH);

delay(2000);

// Now turn off motors

digitalWrite(in1, LOW);
digitalWrite(in2, LOW);
digitalWrite(in3, LOW);
digitalWrite(in4, LOW);

}
void demoTwo()

{

// This function will run the motors acrossthe range of possible speeds
// Note that maximum speed is determined by the motor itself and the operating voltage

// Turn on motors

digitalWrite(in1, LOW);
digitalWrite(in2, HIGH);
digitalWrite(in3, LOW);
digitalWrite(in4, HIGH);

// Accelerate from zero to maximum speed

for (int i = 0; i == 256; i++) /* Equality check is == assignment is = */

{ /* Wrong bracket, sb { */

analogWrite(enA, i);
analogWrite(enB, i);

delay(20);

} /* Wrong bracket, sb } */

// Decelerate motors from maximum speed to zero
for(int i = 255; i >= 0; i--) /* The ; ends the loop and also the scope of i causing error re undeclared in line 103 */

{ /* Wrong bracket, sb { */

analogWrite(enA, i); /* , between args, not ; */
analogWrite(enB, i); /* , between args, not ; */

delay(20);

}

// Now turn off motors

digitalWrite(in1, LOW);
digitalWrite(in2, LOW);
digitalWrite(in3, LOW);
digitalWrite(in4, LOW);

}

void loop()

{

demo0ne(); /* Missing ; */

delay(1000);

demoTwo(); /* Missing ; */

delay(1000);

}

@zander Thank You Very Much Ron.

I am very new at writing sketches as you can see.

You have been very helpful.

I do not know how to fix errors at all thank you