HOW TO INCREASE THE PWM FREQUENCY OF THE ARDUINO ON PINS 10, 11(OC1B, OC2A)

 

This post explains about how to increase the pwm frequency of digital pins 10 and 11 on Uno, Nano, mini. The default frequency is nearly 500 Hz this trick helps to increase to 31.3 kHz.

Now 500 Hz is ok for many speed and analog controls but we need more frequency for high speed controlling and high speed switching like buck and boost, switch mode power supply, RF etc. Applications.

That being said how do we do that…? Well the pwm pins are actually wired internally to timer circuits. The Arduino (Uno, Mini and Nano) have 3 timers Timer 0, 1, 2.

[NOTE: this technique will helps to increase frequency not the bit rate, the bit rate is only 8-bit no matter what (MAX 256bits)]

Here we need to change those timers1 “B” (OC1B or 10 pin), timer2 “A” (OC2A or 11pin). By changing the Pre-scaler value, changing the registers value we can accomplish that.

Timer2 (8bit) PWM:

PWM output 2A = pin11 = PORTB_bit3: PWM duty register = OCR2A
Fast PWM (TOP=0xff), and pre-scaler= 1 are as follows:

“TCCR2B = TCCR2B & B11111000 | B00000001; // put this line in void setup () for 31.37 kHz on pin 11 and 3“

Down below the register of the TCCR2B:

7                6            5            4            3            2            1        0

FOC2A

FOC2B

WGM20

WGM21

WGM22

CS22

CS21

CS20

Don’t touch 7 and 6 bits if so they disable pwm mode to compare mode.

We need to change WGM20, 21, 22 registers value for pre-scaler, I’m setting to pre-scaler 1. Hence the math goes like this:

Period T = (1/16 MHz/1)*256 = 0.016ms => Freq F = 1/T = 1/0.016ms = 62.5 KHZ

 

Timer1 (16bit) PWM:

TCCR1B = TCCR1B & B11111000 | B00000001; // put this in void setup () for generating pwm frequency of 31.383 KHZ

The above line of code helps you to change the TCCR1B register
TCCR1B:
7                 6             5          4            3               2        1           0

ICNC1

ICES1

WGM13

WGM12

CS12

CS11

CS10

 
We need to change CS12, 11, 10 bits to 001 to set pre-scaler 1

Down below an example sketch for Arduino PWM :

further more of register manipulation see this article

 

       

           
void setup() 
{

    Serial.begin(9600);

    Serial.print(TCCR1B,BIN); //tests what is default in TCCR1B and returns inbinary

     TCCR1B = TCCR1B & B11111000 | B00000001;
      // put your setup code here, to run once:
      //put this in void setup () for generating pwm frequency of //31.383 KHZ

      pinMode(10, OUTPUT);
    }

void loop() 
{

  //for(int i=0; i<256 0.9="" 255="" analogwrite="" delay="" for="" i="" int="" j="">=0 ; j-=5){

      analogWrite(10, j);

     delay(30);
     }
  */
}