How to re-enable the timer after a One pulse goes off (OPM)?

[CLeo.1]

Hi guys I am using the stm32h753zi MCU and writing my own drivers to use the WS2812B led strip.

It uses a PWM to determine how much of the RGB you want.

I got the PWM part down and the OPM done, the problem is that I want to send let say a duty cycle of 80% follow by a 32% duty Cycle. I got it working for sending one burst but noted in the datasheet the OPM disables the CEN, however I can never re-enable it?

Is that how OPM works? One time and thats it?

Essentially sending a duty cycle of 80% = 1 and sending a duty cycle of 32% = 0, so thats why I want to send it in pulses in PWM form.

EDIT: 1 Using the TIM15 configured in PWM mode with DMA. The DMA will transfer from a buffer into CCR1 to alter the PW on the fly.

Code:

Timer Setup with DMA

/*
 * Timer_Driver.c
 *
 * Created on: Jan. 8, 2021
 * Author: Christopher
 */
 
 
#include "Timer.h"
 
void init_Timer(uint16_t * RGB_Array) {
 
	RCC->APB2ENR |= RCC_APB2ENR_TIM15EN;
 
	GPIOA->MODER &= ~GPIO_MODER_MODE2;
	GPIOA->MODER |= GPIO_MODER_MODE2_ALT;
 
	GPIOA->OSPEEDR &= ~GPIO_OSPEEDR_OSPEED2;
	GPIOA->OSPEEDR |= GPIO_OSPEEDR_OSPEED2_VERY_HIGH;
 
	GPIOA->AFR[0] &= ~GPIO_AFRL_AFSEL2;
	GPIOA->AFR[0] |= GPIO_AFRL_AFSEL2_TIM15;
 
	TIM15->CCMR1 &= ~TIM_CCMR1_CC1S;
	TIM15->CCMR1 |= TIM_CCMR1_CC1S_OUTPUT_MODE;
 
	TIM15->CCMR1 &= ~TIM_CCMR1_OC1M;
	TIM15->CCMR1 |= TIM_CCMR1_OC1M_PWM1;
 
	TIM15->ARR = 0x12B;
	TIM15->PSC = 0x00;
 
	TIM15->AF1 &= ~TIM15_AF1_BKINE;
	TIM15->CCMR1 |= TIM_CCMR1_OC1PE;
	TIM15->CR1 |= TIM_CR1_ARPE;
	TIM15->CR1 |= TIM_CR1_URS;
	//TIM15->CR1 |= TIM_CR1_OPM;
	TIM15->DIER |= TIM_DIER_UDE;
 
 
	//TIM15->CCMR1 &= ~TIM_CCMR1_OC1PE;
 
	TIM15->BDTR |= TIM_BDTR_MOE;
	TIM15->CCER |= TIM_CCER_CC1E;
	//TIM15->CR1 |= TIM_CR1_CEN;
 
	RCC -> AHB1ENR |= RCC_AHB1ENR_DMA1EN;
 
 
	 DMAMUX1_Channel2 -> CCR |= DMAMUX_CxCR_DMAREQ_ID_TIM15_CH1;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_CT;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_PL;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_MSIZE;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_PSIZE;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_MINC;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_CIRC;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_DIR;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_PFCTRL;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_TCIE;
	 DMA1_Stream2 -> CR &= ~DMA_SxCR_HTIE;
 
	 DMA1_Stream2 -> CR |= DMA_SxCR_CT_MEM0;
	 DMA1_Stream2 -> CR |= DMA_SxCR_PL_Very_High;
	 DMA1_Stream2 -> CR |= DMA_SxCR_MSIZE_32BIT;
	 DMA1_Stream2 -> CR |= DMA_SxCR_PSIZE_32BIT;
	 DMA1_Stream2 -> CR |= DMA_SxCR_MINC;
	 DMA1_Stream2 -> CR |= DMA_SxCR_CIRC;
	 DMA1_Stream2 -> CR |= DMA_SxCR_DIR_M_TO_P;
	 DMA1_Stream2 -> CR |= DMA_SxCR_PFCTRL_DMAFLOW;
	 //DMA1_Stream2 -> CR |= DMA_SxCR_TCIE;
 
	 DMA1_Stream2 -> NDTR = 25;
 
	 DMA1_Stream2 -> PAR = (int) &TIM15->CCR1;
	 DMA1_Stream2 -> M0AR = (int) RGB_Array;
 
	 DMA1_Stream2 -> CR |= DMA_SxCR_EN;
 
 
 
 
}

Where the Action happens:

uint16_t RED [25] = {0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77,
					 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF,
					 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77, 0x00};
 
uint16_t BLUE [25] = {0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77,
				 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77,
					 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0x00};
 
uint32_t GREEN [25] = {0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF,
					 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77,
					 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77, 0x00};
 
void setLedLights(uint8_t color, uint16_t * RGB_Array) {
 
if (color == 1) {
 
 
	memcpy(RGB_Array, GREEN, sizeof(uint16_t) * 25);
 
 
 
} else if (color == 2) {
 
	memcpy(RGB_Array, RED, sizeof(uint16_t) * 25);
 
 
 
 
 
} else if (color == 3) {
 
	memcpy(RGB_Array, BLUE, sizeof(uint16_t) * 25);
 
 
}
 
TIM15->CR1 |= TIM_CR1_CEN;
 
}

 Picture:

[waclawek.jan]

> OPM disables the CEN, however I can never re-enable it?

Of course you can, simply write 1 to it.

JW

[CLeo.1]

Yeah! Just figured out, I assume it wasnt working because in debug mode it instantly set the CEN = 0 so I couldnt see it turn back on

[CLeo.1]

Updated Post

[TDK]

Since pulses need to be back to back, using a DMA-facilitated mode is a better option here. WS2812B is insanely popular, I'm sure you can find code implementations easily.

This bring up at least 5 unique implementation libraries in the first 10 hits:

https://www.google.com/search?q=WS2812B+stm32+library

This one explains it nicely:

http://www.martinhubacek.cz/arm/improved-stm32-ws2812b-library

[CLeo.1]

Yup! After I posted this I found that website, so I am using the DMA PWM way.

What I have now is

An array of pre calculated PW values for sending 1's and 0's that will transfer from the buffer into the CCR1 TIM so a Memory -> peripheral configuration. Theres no Half nor Full complete interrupt as I dont think I need to know when it finishes it. The TIM15 is configured as a PWM so when CCR1 is updated with the pre-calculated PW it should send the correct 1 and 0 pulse widths.

The problem is the DMA needs to be circular or a one shot transfer? and the PWM produced by TIM15 misses pulses and looks messed up

[TDK]

Good progress, keep going.

Pretty sure PFCTRL should not be set here.

It should be a one-shot transfer unless you want it to loop through the buffer again after it's done sending.

You're transferring 32-bit values while your timer is only 16-bits. I'd change the array to uint16_t values and the memory sizes to half-word. It may be transferring 0x77, then 0x00, then 0x77, then 0x00, etc, which would explain the pattern.

Not sure where you're getting DMAMUX_CxCR_DMAREQ_ID_TIM15_CH1, but it's working so it should be right. There is likely a value in the CubeH7 repo which would be more readable. Not a big deal.

I would use the update event (tim15_up_dma) which will do the transfer on update rather than the ch1 event (tim15_ch1_dma) which does the transfer on a ch1 match. For your particular values, they should behave the same, but if you want 0% or 100% duty cycle, update is going to be better.

[CLeo.1]

Thank you appreciate the kind words!, I find working with I2S easier than TIMERS haha

Okay I got an update for you. Yes that 32bit, I fixed it realized CCR1 is a 16 bit register it did fixed some weird PW I was seeing on the line.

PFCTRL is not set, it puts a 0 to make it a DMA flow controller, I see why you thought that. I could remove it.

TIM15 for whatever reason has 2 DMA request TIM15_CH1_DMA, and TIM15_CH1_UP. I tried the latter but didn't work so I had to use the former.

Picture of the Updated Changes, still not perfect.

 The array for reference:

uint16_t GREEN [25] = {0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF, 0xEF,
		 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77,
					 0x77, 0x77, 0x77, 0x77, 0x77, 0x77, 0x77 ,0x77, 0x00};

Like its outputting 9 0xEF? then the rest looks good, and I don't know about that last one