Nano Timer2 OCR2A & B could not work separately

Projects Programming
1

This is my first time using the Forum.
I have been trying for 2 days to get both works simultaneously but with independent compare match value (Timer2 OCR2A & B) and control its own output accordingly . Each OCR2A and OCR2B has different match compare value. Also each output pin (11 ,3) (OCR2A & B) would be active ( PWM) output for a duration and then OFF for a different duration. I just could not make this works. :tired_face: :disappointed:

Please help me.

The following is my sketch.

#include <Wire.h>

const int ocr2top = 255; //Mode 1 default top xFF.
float i = 0;
float j = 0;

//----------------------------------------------
void setup()
{
// OC2A arduino pin11 (PB3) OC2B arduino pin3 (PD3)

Serial.begin(9600);

// mode1 1 phasecorrection
TCCR2A = (1 << COM2A1)+(1 << COM2B1) + (0 << WGM21) + (1 << WGM20);
// WGM20 set -> Mode 1, phasecorrect xFF top
// COM2A1=1 and COM2B0 = 0 means clear OC2A n B compare match.

TCCR2B = (1 << CS22) + (1 << CS21) + (0 << CS20) + (0 << WGM22); // prescaler

//pinMode(3, OUTPUT); //OCR2B
//pinMode(11, OUTPUT); //OCR2A

delay ( 100);
}
//==================== LOOP ===========================
void loop()
{
// -------------------OCR2A--------------
if (i < 400)
{
i = i + 1;
}
else {
i = 0;
}
if (( i > 0 ) && (i < 4))
{
fun_OCR2A(140);
}
if ((i > 210) && (i < 214))
{
fun_FWDoff();
}
//--------------OCR2B------------
if (j < 600)
{
j = j + 1;
}
else {
j = 0;
}

if (( j > 0 ) && (j < 9 ))
{
fun_OCR2B(204);
}
else if ((j > 300) && (j < 308))
{
fun_REVoff();
}
}
//========= functions ==========================

//--------------------------------------------------------
void fun_FWDoff()
{
OCR2A = 0 ;
digitalWrite (11, LOW);
Serial.print(" OCR2A off= ");
Serial.println(OCR2A);
}
//------------------------------------

void fun_OCR2A(int val)
{
pinMode(11, OUTPUT); //OCR2A
OCR2A = val;
Serial.print(" OCR2A = ");
Serial.println(OCR2A);
}
//--------------------------------------------------------

void fun_REVoff()
{
OCR2B = 0 ;
digitalWrite (3, LOW);
Serial.print(" OCR2B off= ");
Serial.println(OCR2B);
}

//------------------------------------

void fun_OCR2B(int val)
{
pinMode(3, OUTPUT);
OCR2B = val;
Serial.print(" OCR2B = ");
Serial.println(OCR2B);
}

2

Please edit your post to add code tags (select code and use the "</>" editor button).

Please explain what you expect to happen, and what happens instead.

"could not make this works" tells us nothing.

3

It is difficult to tell from your Q, but is the symptom that after some stuff, the PWM part stops working?

If so, it could be in code like this:

Calling digitalWrite() on a timer pin disables the PWM control of the pin and it would need reconfiguring to work again.

Here's the source code of digitalWrite() where it checks to turn off PWM:
ArduinoCore-avr/cores/arduino/wiring_digital.c at 2cebe625833afcdb76cc941ccf90e5f5fefc27a9 · arduino/ArduinoCore-avr · GitHub

1 Like
4

You are using TC2 in Mode-1 to generate Phase Correct PWM signal.
1. Excute a simple program to see PWM signal at DPin-11 (OC2A) and DPin-3 (OC2B) simultaneously.

void setup()
{
    Serial.begin(9600);
    TCCR2A = 0x00;  //always reset 
    TCCR2B = 0x00; //always reset
    TCCR2A = (1<<COM2A1)|((1<<COM2B1) | (0<<WGM21)|(1<<WGM20); //Mode-1
    TCCR2B = (1<<CS22)|(1<<CS21)|(0<<CS20)|(0<<WGM22); //Mode-1 and prescale 256
    pinMode(11, OUTPUT);  //Ch-A
    pinMode(3, OUTPUT);     //Ch-B
    //-------------------------------
    OCR2A = 127;    //50% duty cycle
    OCR2B =  64;    //about 25% duty cycle
}

void loop()
{

}

2. Upload the above sketch and check that you have about 123 Hz (= 16MHz/(256*510) PWM signals at both DPin-11 and Dpin-3 with different duty cycles.

3. If you want to control the duty cycle of Ch-A manually, then connect a 5K pot with A0-pin of UNO and include the following codes in the loop() function. Slowly turn the pot and check that the brightness of a LED connected at DPin-11 changes (modulates).

OCR2A = map(analogRead(A0), 0, 1023, 0, 250);
delay (2000); //test interval
5

THANKS FOR ADVISE. I will repose and will separate the multiple issues with single issue/question. That will be better. The issues could be multiple.

6

thanks for your advise. I had tested with a sketch similar to your and both ports works with pwm ( continuous) and I scoped both and confirmed.

I will repose my question differently so my questions/issues will be address desperately.

7

Please see my other post only focus on one issue only for the time being.

Nano- TIMER2 OCR2A pwm in burst mode cannot control burst duration

8

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