12/9/2023 0 Comments Arduino pwm pin 11 varspeedservoHowever, the designation what channel is assigned to what pin is determined by the PIO Controller Multiplexing tables in the SAM3X8E's datasheet. The REG_PWM_CMR0 register is just the Channel Mode Register for channel 0. For example PWM_CLK_PREA(5) will divide the master clock (84MHz) by 32. The prescalers PREA and PREB are 4-bit values that range from 0 to 15 and correspond to a prescaler of 1 through to 1024. If DIVA or DIVB are between 2-255 the CLKA and CLKB are divided by PREA or PREB then divided by DIVA or DIVB. If DIVA or DIVB are 1 the respective clocks are prescaled by PREA or PREB. If DIVA or DIVB are 0 CLKA and CLKB are turned off respectively. You can then optionally set a prescaler and divisor (or both) for either CLKA or CLKB in the PWM Clock Register (REG_PWM_CLK), for example: REG_PWM_CLK = PWM_CLK_PREA(0) | PWM_CLK_DIVA(42) // Set the PWM clock prescaler and divisor (84MHz/42) If you require more refinement to your clock frequency, it's possible instead to divide down the master clock (84MHz) using one of two clock sources: CLKA or CLKB, like I did with CLKA in the example above: REG_PWM_CMR0 = PWM_CMR_CPRE_CLKA does the same thing, but is useful if you're iterating throught a number of channels. or alternatively: PWM->PWM_CH_NUM.PWM_CMR = PWM_CMR_CPRE_MCK_DIV_2 To divide down by 2 on channel 0: REG_PWM_CMR0 = PWM_CMR_CPRE_MCK_DIV_2 This divides down the Due's master clock running at 84MHz: Yes, on the Due it's possible to change the prescaler for each timer channel using the PWM Channel Mode Register (REG_PWM_CMRx). REG_PWM_SCUC = PWM_SCUC_UPDULOCK // Set the update unlock bit to trigger an update at the end of the next PWM periodĪny way to use simple prescaler change like I did in this example for an individual channel? PWM_ENA_CHID3 | PWM_ENA_CHID2 | PWM_ENA_CHID1 | PWM_ENA_CHID0 įor (uint8_t i = 0 i PWM_CH_NUM.PWM_CDTYUPD = 1050 // Set the PWM duty cycle to 50% (2100/2=1050) on all channels REG_PWM_ENA = PWM_ENA_CHID7 | PWM_ENA_CHID6 | PWM_ENA_CHID5 | PWM_ENA_CHID4 | // Enable all PWM channels REG_PWM_ENA = PWM_ENA_CHID0 // Enable the PWM channels, (only need to set channel 0 for synchronous mode) PWM->PWM_CH_NUM.PWM_CPRD = 2100 // Set the PWM period register 84MHz/(40kHz)=2100 PWM_SCM_SYNC3 | PWM_SCM_SYNC2 | PWM_SCM_SYNC1 | PWM_SCM_SYNC0 įor (uint8_t i = 0 i PWM_CH_NUM.PWM_CMR = PWM_CMR_CPRE_CLKA // Enable single slope PWM and set the clock source as CLKA REG_PWM_SCM |= PWM_SCM_SYNC7 | PWM_SCM_SYNC6 | PWM_SCM_SYNC5 | PWM_SCM_SYNC4 | // Set the PWM channels as synchronous REG_PWM_CLK = PWM_CLK_PREA(0) | PWM_CLK_DIVA(1) // Set the PWM clock A rate to 84MHz (84MHz/1) REG_PIOC_PDR |= PIO_PDR_P24 | PIO_PDR_P23 | PIO_PDR_P22 | PIO_PDR_P21 // Set the port C PWM pins to outputs ![]() 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_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_ABSR |= PIO_ABSR_P19 | PIO_ABSR_P18 | PIO_ABSR_P17 | PIO_ABSR_P16 // Set the port B PWM pins to peripheral type B REG_PMC_PCER1 |= PMC_PCER1_PID36 // Enable PWM PWM set-up on pins DAC1, A8, A9, A10, D9, D8, D7 and D6 for channels 0 through to 7 respectively 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 The following code outputs a 40kHz signal on all 8 channels. The PWM controller used on the Due has 8 channels. It might be on the DAC1 pin, but the pins on the SAM3X8E microcontroller have multiple functions. ![]() This is one of the PWM channels, channel 0. ![]() Using the buffered register outputs the signal on the next timer cycle, preventing changes from causing glitches on your outputs: REG_PWM_CDTYUPD0 = 1050 The duty cycle can be changed by loading the buffered duty cycle update register REG_PWM_CDTYUPD0 with a value between, (0 to 100% duty cycle). What do you mean by analog input, if you require the Due to produce a PWM output? Thanks but a buck converter needs to be controlled with an analog input with variable duty cycle.
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