***4 days to deadline*** (PWM & tone()function interference problem???)

Hi everyone,

I'm working on a rather simple project for school and it's due in 4 days. Your help would be greatly appreaciated.

So basically I'm controlling two LED's via PWM lines from 2 Potentiometer inputs. The output of the potentiometers are map() from 0 - 1023 to 0-255.

Then, I have a potentiometer controlling an 8 ohm speaker via the tone() function. The potentiometer just cycles through different notes on a simple musical scale depending on the position of the pot.

The problem is that after turning the pot for the speaker fully right then fully left a few times the speaker emits a high pitched sound and the musical scale is not controllobale by the pot until arduino is reset(by pressing the button on the board.) I think it is due to PWM interference from the LED's because when I remove the code for PWMed Led's, the time until the problem occurs is greatly extended(up to around 60 fully left and fully right turned on the potentiometer).

Here is my code(there is also a seperate pitches.h page that just lists the frequencies for each note e.g. NOTE_C3 etc.):

/*
 2 PWM controlled LED's
 1 PWM controlled 8 Ohm speaker(stereo)

 LED's controlled by 2 potentiometers
 Speaker controlled by 1 potentiometer

 Variables for pin numbers, brightness, and values
 */


 #include "pitches.h"
 //just different notes on a scale
int melody[] = {0,NOTE_C3, NOTE_CS3,NOTE_D3 ,NOTE_DS3,NOTE_E3 ,NOTE_F3, NOTE_FS3,NOTE_G3, NOTE_GS3,NOTE_A3 ,NOTE_AS3,NOTE_B3, NOTE_C4 };

int led1 = 5;
int led2 = 6;

int brightnessled1 = 0;
int brightnessled2 = 0;

int potval1 = 0;
int potval2 = 0;
int potvalforspeaker;

void setup() {
  pinMode (led1, OUTPUT);
  pinMode (led2, OUTPUT);
}

void loop() {
  //for speakers
  potvalforspeaker = analogRead(5);
  int thisPitch = map(potvalforspeaker, 0, 1023, 0, 13);
  tone(8, melody[thisPitch], 15);

 //for LED's
  potval1 = analogRead(1);
  potval2 = analogRead(2);
  brightnessled1 = map(potval1, 0, 1023, 0, 255);
  brightnessled2 = map(potval2, 0, 1023, 0, 255);
  analogWrite(led1, brightnessled1);
  analogWrite(led2, brightnessled2);
  
}

Just a thought, have you checked to see that the PWM pins you are using and your pitch.h/tone code are using conflicting hardware timers?

Lefty

retrolefty: Just a thought, have you checked to see that the PWM pins you are using and your pitch.h/tone code are using conflicting hardware timers?

No I haven't, where I can I find which pwm pins are for which timers??

Thanks

Numex106:

retrolefty: Just a thought, have you checked to see that the PWM pins you are using and your pitch.h/tone code are using conflicting hardware timers?

No I haven't, where I can I find which pwm pins are for which timers??

Thanks

http://www.arduino.cc/playground/Main/TimerPWMCheatsheet

You will have to check the tone code to see which timers it uses.

Lefty

controlling an 8 ohm speaker

Connected directly to an Arduino pin?

Well, I researched the "pitches.h" file and it doesn't specify any timers. In fact, all "pitches.h" contains is a list of defined constants that are linked to note names. So the "pitches.h" doesn't deal with the use of timers directly. That is still handles by the Tone() function.

To make the pitches.h file, click on the "new Tab" button in the upper right hand corner of the window. It looks like this:

The paste in the following code: /************************************************* * Public Constants *************************************************/

define NOTE_B0 31

define NOTE_C1 33

define NOTE_CS1 35

define NOTE_D1 37

define NOTE_DS1 39

define NOTE_E1 41

define NOTE_F1 44

define NOTE_FS1 46

define NOTE_G1 49

define NOTE_GS1 52

define NOTE_A1 55

define NOTE_AS1 58

define NOTE_B1 62

define NOTE_C2 65

define NOTE_CS2 69

define NOTE_D2 73

define NOTE_DS2 78

define NOTE_E2 82

define NOTE_F2 87

define NOTE_FS2 93

define NOTE_G2 98

define NOTE_GS2 104

define NOTE_A2 110

define NOTE_AS2 117

define NOTE_B2 123

define NOTE_C3 131

define NOTE_CS3 139

define NOTE_D3 147

define NOTE_DS3 156

define NOTE_E3 165

define NOTE_F3 175

define NOTE_FS3 185

define NOTE_G3 196

define NOTE_GS3 208

define NOTE_A3 220

define NOTE_AS3 233

define NOTE_B3 247

define NOTE_C4 262

define NOTE_CS4 277

define NOTE_D4 294

define NOTE_DS4 311

define NOTE_E4 330

define NOTE_F4 349

define NOTE_FS4 370

define NOTE_G4 392

define NOTE_GS4 415

define NOTE_A4 440

define NOTE_AS4 466

define NOTE_B4 494

define NOTE_C5 523

define NOTE_CS5 554

define NOTE_D5 587

define NOTE_DS5 622

define NOTE_E5 659

define NOTE_F5 698

define NOTE_FS5 740

define NOTE_G5 784

define NOTE_GS5 831

define NOTE_A5 880

define NOTE_AS5 932

define NOTE_B5 988

define NOTE_C6 1047

define NOTE_CS6 1109

define NOTE_D6 1175

define NOTE_DS6 1245

define NOTE_E6 1319

define NOTE_F6 1397

define NOTE_FS6 1480

define NOTE_G6 1568

define NOTE_GS6 1661

define NOTE_A6 1760

define NOTE_AS6 1865

define NOTE_B6 1976

define NOTE_C7 2093

define NOTE_CS7 2217

define NOTE_D7 2349

define NOTE_DS7 2489

define NOTE_E7 2637

define NOTE_F7 2794

define NOTE_FS7 2960

define NOTE_G7 3136

define NOTE_GS7 3322

define NOTE_A7 3520

define NOTE_AS7 3729

define NOTE_B7 3951

define NOTE_C8 4186

define NOTE_CS8 4435

define NOTE_D8 4699

define NOTE_DS8 4978

Lefty, you said "check the tone code to see which timers it uses" ... I would like to be able to do that but I don't have any idea just HOW I could do that. Where/how do I find a listing of that code?

Well it doesn't appear to be a timer conflict. From the Arduino reference for tone:

Use of the tone() function will interfere with PWM output on pins 3 and 11 (on boards other than the Mega).

http://arduino.cc/en/Reference/Tone

Lefty

Hiya!

Strange this hasn't been asked yet, but what board are you using? It will be helpful in tracking things down. As well, what version of the IDE are you using?

Next, if I understand correctly, you're saying that the code goes wonky when the pot controlling the tone() values is moved to its extents repeatedly? And you say that regardless of whether the PWM (analogWrite()) code is in place, that the code goes wonky - just the length of time to failure is different?

If the board you are using is a Duemilanove or an Uno, then retrolefty is correct, that there will be no "interference" between tone() and analogWrite().

I've tested the code on a rEDI board, and the sketch works fine.

As I think CodingBadly has asked - are you connecting the speaker directly to a pin? If so, this can be seriously dangerous to the controller. If you do not put a resistor (and preferably a flyback diode - although not strictly necessary as long as you use a high enough series resistor) in series with the speaker, you will have large voltages being sent back into the controller potentially causing latchup - i.e. causing the controller to stop working.

More references: http://www.wiring.org.co/learning/basics/tonemelody.html http://code.google.com/p/rogue-code/wiki/ToneLibraryDocumentation

Strange this hasn't been asked yet, but what board are you using? It will be helpful in tracking things down. As well, what version of the IDE are you using?

Duemilanove + latest IDE 0022

Next, if I understand correctly, you're saying that the code goes wonky when the pot controlling the tone() values is moved to its extents repeatedly? And you say that regardless of whether the PWM (analogWrite()) code is in place, that the code goes wonky - just the length of time to failure is different?

Correct, when i remove the analogWrite() code for the LED's time until failure is increased from around 3 extents to 20.

are you connecting the speaker directly to a pin?

yes, I'm using a resistor as stated by the tone() example diagram on arduino.cc>learning>tone()

A slight update: If you look at my code you will see I have an array with the frequencies in order. the first thing(forgot what it's called) in the array is stated 0 frequency it seems that if I just this to 1 then it seems to be working except every second a pulse is generated on the speaker which is about as annoying as the high pitched squeel it emits when not working. Also, if I do not turn the pot fully left so it doesn't reach that 0Hz frequency it works. (so full right works, unless you turn it fully left)

Thanks for all the help so far :)

Oh right, I forgot we're using Arduino. ;)

Try this in your code:

  int thisPitch = map(potvalforspeaker, 0, 1023, 0, 13);
  if (thisPitch > 0)
    tone(8, melody[thisPitch], 15);
  else
    noTone(8);

b

Numex106:

are you connecting the speaker directly to a pin?

yes, I’m using a resistor as stated by the tone() example diagram on arduino.cc>learning>tone()

5 volts / 108 ohms = 0.0463 amps = 46.3 milliamps

From the datasheet…

28.1 Absolute Maximum Ratings*

DC Current per I/O Pin … 40.0 mA

*NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Correct, when i remove the analogWrite() code for the LED’s time until failure is increased from around 3 extents to 20.

You are running WAY TOO MUCH CURRENT through the processor. My suspicion is that the processor is overheating and then stops functioning correctly. Even if I’m wrong, YOU NEED TO REDUCE THE CURRENT.

Oh sheesh… I didn’t know you were using only 100 Ohms. Definitely needs to be more like 1K Ohm.

This is what I specify in the Tone library.

http://code.google.com/p/rogue-code/wiki/ToneLibraryDocumentation#Hardware_Connections/Requirements

The diagram I use on the wiki page is from Tom Igoe’s examples, and, ugh, is it wrong, for so many reasons. I’m going to change it now.

Further to what CodingBadly has written - When you have the tone() set @ 0 Hz (i.e. the pin is either ON or OFF solid) - the MAXIMUM current will flow through the pin if it is set HIGH, so it will definite exceed the specifications and likely cause a latchup.

Finally - the code change I posted MUST be used, because you shouldn’t send a frequency of 0 to tone() in Arduino 0022.

b

So should the tutorial be changed?