MartinL:
Hi buckboostbill,What do you mean by analog input, if you require the Due to produce a PWM output?
The duty cycle can be changed by loading the buffered duty cycle update register REG_PWM_CDTYUPD0 with a value between 0 and 2100, (0 to 100% duty cycle). Using the buffered register outputs the signal on the next timer cycle, preventing changes from causing glitches on your outputs:
REG_PWM_CDTYUPD0 = 1050;This is one of the PWM channels, channel 0. It might be on the DAC1 pin, but the pins on the SAM3X8E microcontroller have multiple functions.
The PWM controller used on the Due has 8 channels. The following code outputs a 40kHz signal on all 8 channels. I've commented out the code that'll allow you to also synchronize these channels:
// Enable single slope, 11-bit resolution PWM at 40kHz on 8 channels
void setup() {
// PWM set-up on pins DAC1, A8, A9, A10, D9, D8, D7 and D6 for channels 0 through to 7 respectively
REG_PMC_PCER1 |= PMC_PCER1_PID36; // Enable PWM
REG_PIOB_ABSR |= PIO_ABSR_P19 | PIO_ABSR_P18 | PIO_ABSR_P17 | PIO_ABSR_P16; // Set the port B PWM pins to peripheral type B
REG_PIOC_ABSR |= PIO_ABSR_P24 | PIO_ABSR_P23 | PIO_ABSR_P22 | PIO_ABSR_P21; // Set the port C PWM pins to peripheral type B
REG_PIOB_PDR |= PIO_PDR_P19 | PIO_PDR_P18 | PIO_PDR_P17 | PIO_PDR_P16; // Set the port B PWM pins to outputs
REG_PIOC_PDR |= PIO_PDR_P24 | PIO_PDR_P23 | PIO_PDR_P22 | PIO_PDR_P21; // Set the port C PWM pins to outputs
REG_PWM_CLK = PWM_CLK_PREA(0) | PWM_CLK_DIVA(1); // Set the PWM clock A rate to 84MHz (84MHz/1)
//REG_PWM_SCM |= PWM_SCM_SYNC7 | PWM_SCM_SYNC6 | PWM_SCM_SYNC5 | PWM_SCM_SYNC4 | // Set the PWM channels as synchronous
// PWM_SCM_SYNC3 | PWM_SCM_SYNC2 | PWM_SCM_SYNC1 | PWM_SCM_SYNC0;
for (uint8_t i = 0; i < PWMCH_NUM_NUMBER; i++) // Loop for each PWM channel (8 in total)
{
PWM->PWM_CH_NUM[i].PWM_CMR = PWM_CMR_CPRE_CLKA; // Enable single slope PWM and set the clock source as CLKA
PWM->PWM_CH_NUM[i].PWM_CPRD = 2100; // Set the PWM period register 84MHz/(40kHz)=2100;
}
//REG_PWM_ENA = PWM_ENA_CHID0; // Enable the PWM channels, (only need to set channel 0 for synchronous mode)
REG_PWM_ENA = PWM_ENA_CHID7 | PWM_ENA_CHID6 | PWM_ENA_CHID5 | PWM_ENA_CHID4 | // Enable all PWM channels
PWM_ENA_CHID3 | PWM_ENA_CHID2 | PWM_ENA_CHID1 | PWM_ENA_CHID0;
for (uint8_t i = 0; i < PWMCH_NUM_NUMBER; i++) // Loop for each PWM channel (8 in total)
{
PWM->PWM_CH_NUM[i].PWM_CDTYUPD = 1050; // Set the PWM duty cycle to 50% (2100/2=1050) on all channels
}
//REG_PWM_SCUC = PWM_SCUC_UPDULOCK; // Set the update unlock bit to trigger an update at the end of the next PWM period
}
void loop() {}
Can you explain it to me? I can use only 8 PWM pins. And can I add 2 pins, for example 2 pins D5 and DAC1?
In my code I add pins ( PIO_ABSR_P15 and PIO_ABSR_P25), but I don't understand how use 10 PWM pins, because in DUE we have only 8 PWM channels (PWM_ENA_CHIDx).