Manual PWM Output for dimmed light

Archive
1

Hi Everybody,

I am new to arducopter, I have a nicely flying DIY-Quadcopter which I just recently pimped with a few LEDs. They are very bright, so I would like to dim them a bit using PWM. I just didnt find any way to do this in the mission planner or elsewhere, so I think I have to program this manually in the user hookup functions.
I have done a lot of µC programming, so C++ is not a problem for me. Still I dont know the Arducopter program structure very well yet.

I tried the following code in the User Hook (after enableing the userhook in the config file)

void userhook_init()
{
hal_mpng.rcout->enable_ch(CH_11);
hal_mpng.rcout->set_freq(_BV(CH_11), 400);
hal_mpng.rcout->write(CH_11, (uint16_t)200);
}

But this does not result in any Output on the pin. Is there somebody with experience on user hook programming? Any help would be appreciated.

Thanks,

Michael

2

Just program the PWM yourself. See the Atmel reference manual for the ATmega1280/2560. Since you have uController experience, this should be no problem! here is some sample code:
void StopPWM(void)
{
TCCR2A=0;
}
void StartPWM(void)
{
// Use internal clock (datasheet p.160)
ASSR &= ~(_BV(EXCLK) | _BV(AS2));
//fixed on pin 11 and 12
//pinMode(12,OUTPUT);
// pinMode(speakerPin, OUTPUT); //OC1A

TCCR1A = _BV(COM1A0) | _BV(COM1B0) |_BV(WGM11)| _BV(WGM10);
TCCR1B = _BV(WGM13) | _BV(CS11);  // /8      // no prescaling ( div by 1 )

 // Set initial pulse width to the first sample.
OCR1A = 1000;

}
However, since you are into the code, you might try just a simple on off of the port bit and a software timer using the 100hz loop in ArduCopter. It wouldn’t be PWM, but it would still dim the LED.
Good luck!

3

[quote=“tbrkfd1”]Just program the PWM yourself. See the Atmel reference manual for the ATmega1280/2560. Since you have uController experience, this should be no problem! here is some sample code:
void StopPWM(void)
{
TCCR2A=0;
}
void StartPWM(void)
{
// Use internal clock (datasheet p.160)
ASSR &= ~(_BV(EXCLK) | _BV(AS2));
//fixed on pin 11 and 12
//pinMode(12,OUTPUT);
// pinMode(speakerPin, OUTPUT); //OC1A

TCCR1A = _BV(COM1A0) | _BV(COM1B0) |_BV(WGM11)| _BV(WGM10);
TCCR1B = _BV(WGM13) | _BV(CS11);  // /8      // no prescaling ( div by 1 )

 // Set initial pulse width to the first sample.
OCR1A = 1000;

}
However, since you are into the code, you might try just a simple on off of the port bit and a software timer using the 100hz loop in ArduCopter. It wouldn’t be PWM, but it would still dim the LED.
Good luck![/quote]

Hi tbrkfd1,
thanks for your reply. Did you use this code on an arducopter? I actually thought about doing it myself manually, but I am not sure which timers are used by the rest of the software already, and I dont want to corrupt the normal stuff. Also I never found a schematic of my board (Crius AIO), so I am not 100% sure about the pin configs. This is why I thought using the ARM PWM functions should make it much easier, because the board can handle 8 Motors -> 8 PWM outputs, of which 4 of them are not used.

Michael

4

I just got it working, actually it is quite simple once you know how to do it:

void userhook_init()
{

  hal_mpng.rcout->enable_ch(CH_8);

  hal_mpng.rcout->write(CH_8, (uint16_t)400);
  

}
#endif




#ifdef USERHOOK_MEDIUMLOOP
void userhook_MediumLoop()
{
  int16_t licht_kanal = hal_mpng.rcin->read(CH_6)-1000;
  
  if(licht_kanal < 0) licht_kanal = 0;
  if(licht_kanal > 1000) licht_kanal = 1000;
  
  float licht = licht_kanal;

  licht = licht*licht;
  licht /= 1000;  
  licht *= 2.3f;

    hal_mpng.rcout->write(CH_8, (uint16_t)licht);

  
}
#endif

in addition, you have to modify the RCOutput file and there specificly the write-function to remove the period-constrain for the PWM output channel (we want PWM to start from 0%) :

[code][code]void MPNGRCOutput::write(uint8_t ch, uint16_t period_us) {
/* constrain, then scale from 1us resolution (input units)

  • to 0.5us (timer units) */

uint16_t pwm;
if(ch != CH_8)
pwm = constrain_period(period_us) << 1;
else
pwm = period_us <<1;

switch(ch)
{
	case 0:  OCR3A = pwm; break; //5
	case 1:  OCR4A = pwm; break; //6
	case 2:  OCR3B = pwm; break; //2
	case 3:  OCR3C = pwm; break; //3
	case 4:  OCR5C = pwm; break; //5
	case 5:  OCR5B = pwm; break; //6
	case 6:  OCR4B = pwm; break; //7
	case 7:  OCR4C = pwm; break; //8
	case 9:  OCR1A = pwm; break; //10
	case 10: OCR1B = pwm; break; //11
}

}[/code][/code]