ATtinyx5: PWM on pin 4 (Arduino 1.0.6)

[ivazqueznet]

I couldn't get analogWrite(3, x) to work properly, but setting GTCCR[6:4] to 0x5 and OCR1B to x let it work.

[oddstr13]

After a few hours of pulling my hair, I've managed to figure this out.
Finally, three PWM outputs!
Here is a Random fading RGB LED, now finally fading also it's B from the Attiny85.
Based on the fade example sketch that comes with the Arduino.

/*
 Fade

 This example shows how to fade an LED on pin 9
 using the analogWrite() function.

 This example code is in the public domain.
 */

int ledR = 0;           // the pin that the LED is attached to
int ledG = 1;
int ledB = 4;

// the setup routine runs once when you press reset:
void setup()  { 
  // declare pin 9 to be an output:
  pinMode(ledR, OUTPUT);
  pinMode(ledG, OUTPUT);
  pinMode(ledB, OUTPUT);
  randomSeed(analogRead(0));
  //Serial.begin(115200);
  GTCCR |= 0b01010000;
  GTCCR &= 0b11011111;
} 

byte valueR = 0;
byte valueG = 0;
byte valueB = 0;
byte targetR = 0;
byte targetG = 0;
byte targetB = 0;

// the loop routine runs over and over again forever:
void loop()  { 
  // set the brightness of pin 9:
  analogWrite(ledR, valueR);
  analogWrite(ledG, valueG);
  //analogWrite(ledB, valueB);
  OCR1B = valueB;
  if (valueR == targetR && valueG == targetG && valueB == targetB) {
      //Serial.println("Change done.");
      //delay(30);
      targetR = (byte) random(255);
      targetG = (byte) random(255);
      targetB = (byte) random(255);

      /*
      Serial.print("0x");
      char hexR[3];
      char hexG[3];
      char hexB[3];
      sprintf(hexR, "%02x", targetR);
      sprintf(hexG, "%02x", targetG);
      sprintf(hexB, "%02x", targetB);
      Serial.print(hexR);
      Serial.print(hexG);
      Serial.print(hexB);
      Serial.println();
      */
  }
  if (valueR < targetR) {
      valueR += 1;
  } else if (valueR > targetR) {
      valueR -= 1;
  }
  if (valueG < targetG) {
      valueG += 1;
  } else if (valueG > targetG) {
      valueG -= 1;
  }
  if (valueB < targetB) {
      valueB += 1;
  } else if (valueB > targetB) {
      valueB -= 1;
  }

  // Adjust delay to change cycling speed
  delay(10);                            
}

I hope this saves the next poor soul coming along from a few hours of pulling their hair :)
Also please correct me if i missunderstood the GTCCR flags, but it seems to be working for me

[mrakuaku]

Thanks so much @oddstr13! Works great for me! and yes it saved me from going bald :) Which is the actual line that is activating PB4 as PWM? is it
" GTCCR |= 0b01010000;
GTCCR &= 0b11011111;"
or
"OCR1B = valueB;"
... or another one?

[oddstr13]

@mrakuaku the GTCCR activates PWM on the pin, OCR1B = value; is basicly analogWrite(ledB, value);

[damellis]

I fixed this for Arduino 1.5.x with 4284860

[mrakuaku]

@oddstr13, the red and green LEDs never seem to go on at the same time. Could this be because the PWM's are interfering with each other somehow? I tried another colour fading code, which I modified to include
"GTCCR |= 0b01010000;
GTCCR &= 0b11011111;"
and
"OCR1B = valueB;"
and noticed that they can fade in and out by them selves, and with the blue, but not with each other.
Do you have any suggestions on how to fix this?

Thanks

[damellis]

I believe Arduino 1.0.6 adds support for initVariant(), so it should be possible to get the third PWM working there too (along with 1.5.x). Anyone want to take a shot at it?

[oddstr13]

@mrakuaku First off, let me appologize for my late reply.
Make sure you use individual resistors for each of the colors, not one on the common lead. Using just one resistor results in erratic behavior. This puzzled me for a while, and I should probably have mentioned that in the original message.

I should also note that I have not worked on this since my initial experiments a year ago.

[damellis]

Fixed for 1.0.6 too.