Hi rmay_pci,
Pin 9 and 10 control the output of both phase and phase and frequency correct PWM on the Arduino Uno. At the risk of going off topic the following code for the Uno sets up two servos at 50Hz. The ICR1 register controls the frequency, for example: 20000 = 50Hz, 10000 = 100Hz, 2500 = 400Hz. The OCR1A and OCR1B registers control the duty cycle. If you're using servos just load them with a value between 1000 and 2000, with 1500 being the center point of the servo. Or, if you need a 50% duty cycle with a value that is half ICR1. However, using this method prevents you from using libraries that also use timer1, for instance the servo library.
void setup() {
// Initialise timer 1 for phase and frequency correct PWM
pinMode(9, OUTPUT); // Set digital pin 9 (D9) to an output
pinMode(10, OUTPUT); // Set digital pin 10 (D10) to an output
TCCR1A = _BV(COM1A1) | _BV(COM1B1); // Enable the PWM outputs OC1A, and OC1B on digital pins 9, 10
TCCR1B = _BV(WGM13) | _BV(CS11); // Set phase and frequency correct PWM and prescaler of 8 on timer 1
ICR1 = 20000; // Set the PWM frequency to 50Hz
OCR1A = 1500; // Centre the servo on D9
OCR1B = 1500; // Centre the servo on D10
}
void loop() {
OCR1A = 1000; // Move the servo to min position on D9
OCR1B = 1000; // Move the servo to min position on D10
delay(1000); // Wait for 1 second
OCR1A = 2000; // Move the servo to max position on D9
OCR1B = 2000; // Move the servo to max position on D10
delay(1000); // Wait for 1 second
}
Back to the Zero. It's internally more flexible than the older AVR processors, so it does require more extensive set-up, but much of it's just routing the processor's generic clock to the appropriate timer and hooking up the correct pins for output. Once that's out of the way, it's pretty much the same as the AVR.
Here's similar code for the Zero, but sets up 4 servos at 50Hz on digital pins D2, D5, D6 and D7 using the TCC0 timer. The REG_TCC0_PER register is equivalent of ICR1 and the REG_TCC0_CCBx the OCR1x registers:
// Output 50Hz PWM on timer TCC0 (14-bit resolution)
void setup()
{
REG_GCLK_GENDIV = GCLK_GENDIV_DIV(3) | // Divide the 48MHz clock source by divisor 3: 48MHz/3=16MHz
GCLK_GENDIV_ID(4); // Select Generic Clock (GCLK) 4
while (GCLK->STATUS.bit.SYNCBUSY); // Wait for synchronization
REG_GCLK_GENCTRL = GCLK_GENCTRL_IDC | // Set the duty cycle to 50/50 HIGH/LOW
GCLK_GENCTRL_GENEN | // Enable GCLK4
GCLK_GENCTRL_SRC_DFLL48M | // Set the 48MHz clock source
GCLK_GENCTRL_ID(4); // Select GCLK4
while (GCLK->STATUS.bit.SYNCBUSY); // Wait for synchronization
// Enable the port multiplexer for the 4 PWM channels: timer TCC0 outputs
const uint8_t CHANNELS = 4;
const uint8_t pwmPins[] = { 2, 5, 6, 7 };
for (uint8_t i = 0; i < CHANNELS; i++)
{
PORT->Group[g_APinDescription[pwmPins[i]].ulPort].PINCFG[g_APinDescription[pwmPins[i]].ulPin].bit.PMUXEN = 1;
}
// Connect the TCC0 timer to the port outputs - port pins are paired odd PMUO and even PMUXE
// F & E specify the timers: TCC0, TCC1 and TCC2
PORT->Group[g_APinDescription[2].ulPort].PMUX[g_APinDescription[2].ulPin >> 1].reg = PORT_PMUX_PMUXO_F | PORT_PMUX_PMUXE_F;
PORT->Group[g_APinDescription[6].ulPort].PMUX[g_APinDescription[6].ulPin >> 1].reg = PORT_PMUX_PMUXO_F | PORT_PMUX_PMUXE_F;
// Feed GCLK4 to TCC0 and TCC1
REG_GCLK_CLKCTRL = GCLK_CLKCTRL_CLKEN | // Enable GCLK4 to TCC0 and TCC1
GCLK_CLKCTRL_GEN_GCLK4 | // Select GCLK4
GCLK_CLKCTRL_ID_TCC0_TCC1; // Feed GCLK4 to TCC0 and TCC1
while (GCLK->STATUS.bit.SYNCBUSY); // Wait for synchronization
// Dual slope PWM operation: timers countinuously count up to PER register value then down 0
REG_TCC0_WAVE |= TCC_WAVE_POL(0xF) | // Reverse the output polarity on all TCC0 outputs
TCC_WAVE_WAVEGEN_DSBOTTOM; // Setup dual slope PWM on TCC0
while (TCC0->SYNCBUSY.bit.WAVE); // Wait for synchronization
// Each timer counts up to a maximum or TOP value set by the PER register,
// this determines the frequency of the PWM operation:
// 20000 = 50Hz, 10000 = 100Hz, 2500 = 400Hz
REG_TCC0_PER = 20000; // Set the frequency of the PWM on TCC0 to 50Hz
while(TCC0->SYNCBUSY.bit.PER);
// The CCBx register value corresponds to the pulsewidth in microseconds (us)
REG_TCC0_CCB0 = 1500; // TCC0 CCB0 - center the servo on D2
while(TCC0->SYNCBUSY.bit.CCB0);
REG_TCC0_CCB1 = 1500; // TCC0 CCB1 - center the servo on D5
while(TCC0->SYNCBUSY.bit.CCB1);
REG_TCC0_CCB2 = 1500; // TCC0 CCB2 - center the servo on D6
while(TCC0->SYNCBUSY.bit.CCB2);
REG_TCC0_CCB3 = 1500; // TCC0 CCB3 - center the servo on D7
while(TCC0->SYNCBUSY.bit.CCB3);
// Divide the 16MHz signal by 8 giving 2MHz (0.5us) TCC0 timer tick and enable the outputs
REG_TCC0_CTRLA |= TCC_CTRLA_PRESCALER_DIV8 | // Divide GCLK4 by 8
TCC_CTRLA_ENABLE; // Enable the TCC0 output
while (TCC0->SYNCBUSY.bit.ENABLE); // Wait for synchronization
}
void loop() { }