10 bit PWM on Arduino UNO

Question

I am using this code to make 10 bit PWM on port number 9, it seems like everything printed is 0,1022 rather than printing 0, 512, 1023. Is there a problem in my code ?

I wired pin9 to A3 to get the output and print it.

 void setup() {
 Serial.begin(9600);
 pinMode(A3,INPUT);
 // Set PB1/2 as outputs.
 DDRB |= (1 << DDB1) | (1 << DDB2);
 TCCR1A =
 (1 << COM1A1) | (1 << COM1B1) |
 // Fast PWM mode.
 (1 << WGM11);
 TCCR1B =
 // Fast PWM mode.
 (1 << WGM12) | (1 << WGM13) |
 // No clock prescaling (fastest possible
 // freq).
 (1 << CS10);
 OCR1A = 0;
 // Set the counter value that corresponds to
 // full duty cycle. For 15-bit PWM use
 // 0x7fff, etc. A lower value for ICR1 will
 // allow a faster PWM frequency.
 ICR1 = 0x03ff;
}
void loop() {
 // Use OCR1A and OCR1B to control the PWM
 // duty cycle. Duty cycle = OCR1A / ICR1.
 // OCR1A controls PWM on pin 9 (PORTB1).
 // OCR1B controls PWM on pin 10 (PORTB2).
 OCR1A = 0x0000;
 delay(500);
 Serial.println(analogRead(A3));
 OCR1A = 0x0200;
 delay(500);
 Serial.println(analogRead(A3));
 OCR1A = 0x03ff;
 delay(500);
 Serial.println(analogRead(A3));
}

The output looks like that:

 0 0 1022 1021 0 1022 1021 0 0 1021 0 1021 1021 0 0 1021 0 0 1022

no data between 0 and 1022 are presented.

thanks.

• Majenko: Do you know even what PWM is...?
• Mostafa Khattab: If you want, you can teach me
• Majenko: Or you could ask Google...

Answer 1

On your code, you using analogRead but declaring the pin (A3) as output. Change it to pinMode(A3,INPUT);

Aside from that, PWM is basically a digital output which changing (HIGH and LOW) at specified frequency. When the result you got is

0 0 1022 1021 0 1022 1021 0 0 1021 0 1021 1021 0 0 1021 0 0 1022

There's nothing wrong. 0 --> LOW, and 1021++ --> HIGH
If you want "measure" something from the PWM, use pulseIn() instead, you can check the documentation here.

If you want to measure the PWM value, I suggest you read:
Can I connect a PWM pin on one Arduino to an analog input on another?

• Mostafa Khattab: Thanks for your note, I just got output like that, which is wrong I guess. 0 0 1022 1021 0 1022 1021 0 0 1021 0 1021 1021 0 0 1021 0 0 1022
• duck: I update my answer
• Mostafa Khattab: Thank you, does that allow me to make arduino output analg data like a potentiometer ?
• duck: Based on @Russell answer from the link above, yes.
• Mostafa Khattab: but, why I don't write that code when I use a potentiometer for example ?