Question

Trying to make a code to change output PWM signal from analog value. The frequency is to be 50kHz or greater. I can get a square wave to work fine when not using the analog reference, but when i try to make it work off the analog reference, the waveform gets all messed up and distorted. I am using arduino nano.

#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
pinMode(3, OUTPUT); // Output pin for OCR2B
int i=1;
int inVal = analogRead(A3);
int outVal = map(inVal, 0, 1023, 1, 10);
// Set up the 250 kHz output (but cro measures only 125 kHz)
TCCR2A = _BV(COM2A1) | _BV(COM2B1) | _BV(WGM21) | _BV(WGM20);
TCCR2B = _BV(WGM22) | _BV(CS20);
OCR2A = 160;
OCR2B = 0;
int n=outVal;

//

while (1) {
_delay_us(10);
if (OCR2B < 1)
OCR2B =OCR2A/outVal;
else
OCR2B = 0;

}
}

Answer 1

Description

Writes an analog value (PWM wave) to a pin. Can be used to light a LED at varying brightnesses or drive a motor at various speeds. After a call to analogWrite(), the pin will generate a steady square wave of the specified duty cycle until the next call to analogWrite() (or a call to digitalRead() or digitalWrite()) on the same pin. The frequency of the PWM signal on most pins is approximately 490 Hz. On the Uno and similar boards, pins 5 and 6 have a frequency of approximately 980 Hz.

On most Arduino boards (those with the ATmega168 or ATmega328P), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 - 13 and 44 - 46. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11.
The Arduino DUE supports analogWrite() on pins 2 through 13, plus pins DAC0 and DAC1. Unlike the PWM pins, DAC0 and DAC1 are Digital to Analog converters, and act as true analog outputs.
You do not need to call pinMode() to set the pin as an output before calling analogWrite().
The analogWrite function has nothing to do with the analog pins or the analogRead function.

Syntax

analogWrite(pin, value)

Parameters

pin: the pin to write to. Allowed data types: int.
value: the duty cycle: between 0 (always off) and 255 (always on). Allowed data types: int

Returns

Nothing

Example Code

Sets the output to the LED proportional to the value read from the potentiometer.

int ledPin = 9;      // LED connected to digital pin 9
int analogPin = 3;   // potentiometer connected to analog pin 3
int val = 0;         // variable to store the read value

void setup() {
  pinMode(ledPin, OUTPUT);  // sets the pin as output
}

void loop() {
  val = analogRead(analogPin);  // read the input pin
  analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023, analogWrite values from 0 to 255
}