TIM15 can't be enabled when OPM bit is set, why?

Hi everyone,

I am having issues getting One Shot Mode enable when using the TIM15. I am currently using the STM32H743ZI as the MCU.

When setting the OPM bit in the TIM15_CR1 register the CEN bit in same register no longer can be enabled for whatever reason. I tried disabling the Auto-reload preload enable (ARPE bit) in the CR1 register but nothing changed.

Code:

LL_DMA_InitTypeDef WS2812B_Config_DMA;
	LL_GPIO_InitTypeDef WS2812B_Config_GPIO;
	LL_TIM_InitTypeDef WS2812B_Config_TIM15;
	LL_TIM_OC_InitTypeDef WS2812B_Config_OC;
	LL_TIM_BDTR_InitTypeDef WS2812B_Config_BDTR;
 
	LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_TIM15);
	LL_AHB4_GRP1_EnableClock(LL_AHB4_GRP1_PERIPH_GPIOA);
	LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_DMA1);
 
	LL_TIM_StructInit(&WS2812B_Config_TIM15);
	LL_TIM_OC_StructInit(&WS2812B_Config_OC);
	LL_TIM_BDTR_StructInit(&WS2812B_Config_BDTR);
	LL_GPIO_StructInit(&WS2812B_Config_GPIO);
	LL_DMA_StructInit(&WS2812B_Config_DMA);
 
	//Configure GPIO
	WS2812B_Config_GPIO.Alternate = LL_GPIO_AF_4;
	WS2812B_Config_GPIO.Mode = LL_GPIO_MODE_ALTERNATE;
	WS2812B_Config_GPIO.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
	WS2812B_Config_GPIO.Pin = LL_GPIO_PIN_2;
	WS2812B_Config_GPIO.Pull = LL_GPIO_PULL_NO;
	WS2812B_Config_GPIO.Speed = LL_GPIO_SPEED_FREQ_VERY_HIGH;
	LL_GPIO_Init(GPIOA, &WS2812B_Config_GPIO);
 
	//Configure DMA
	WS2812B_Config_DMA.Direction = LL_DMA_DIRECTION_MEMORY_TO_PERIPH;
	WS2812B_Config_DMA.FIFOMode = LL_DMA_FIFOMODE_DISABLE;
	WS2812B_Config_DMA.MemBurst = LL_DMA_MBURST_SINGLE;
	WS2812B_Config_DMA.MemoryOrM2MDstAddress = (uint32_t)WS28128B_BUFF;
	WS2812B_Config_DMA.MemoryOrM2MDstDataSize = LL_DMA_MDATAALIGN_HALFWORD;
	WS2812B_Config_DMA.MemoryOrM2MDstIncMode = LL_DMA_MEMORY_INCREMENT;
	WS2812B_Config_DMA.Mode = LL_DMA_MODE_NORMAL;
	WS2812B_Config_DMA.NbData = NUM_LED;
	WS2812B_Config_DMA.PeriphBurst = LL_DMA_PBURST_SINGLE;
	WS2812B_Config_DMA.PeriphOrM2MSrcAddress = (uint32_t)&TIM15->CCR1;
	WS2812B_Config_DMA.PeriphOrM2MSrcDataSize = LL_DMA_PDATAALIGN_HALFWORD;
	WS2812B_Config_DMA.PeriphOrM2MSrcIncMode = LL_DMA_PERIPH_NOINCREMENT;
	WS2812B_Config_DMA.PeriphRequest = LL_DMAMUX1_REQ_TIM15_UP;
	WS2812B_Config_DMA.Priority = LL_DMA_PRIORITY_LOW;
 
	//Interrupt: DMA
	LL_DMA_EnableIT_TC(DMA1, LL_DMA_STREAM_4);
 
	NVIC_EnableIRQ(DMA1_Stream4_IRQn);
	NVIC_SetPriority(DMA1_Stream4_IRQn, 0);
 
	LL_DMA_Init(DMA1, LL_DMA_STREAM_4, &WS2812B_Config_DMA);
 
	WS2812B_Config_TIM15.Autoreload = 240e6/LED_FREQ;
	WS2812B_Config_TIM15.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
	WS2812B_Config_TIM15.CounterMode = LL_TIM_COUNTERMODE_UP;
	WS2812B_Config_TIM15.Prescaler = 0;
	WS2812B_Config_TIM15.RepetitionCounter = 0;
	LL_TIM_Init(TIM15, &WS2812B_Config_TIM15);
 
	WS2812B_Config_OC.CompareValue = 0;
	WS2812B_Config_OC.OCIdleState = LL_TIM_OCIDLESTATE_LOW;
	WS2812B_Config_OC.OCMode = LL_TIM_OCMODE_PWM1;
	WS2812B_Config_OC.OCNIdleState = LL_TIM_OCIDLESTATE_LOW;
	WS2812B_Config_OC.OCNPolarity = LL_TIM_OCPOLARITY_HIGH;
	WS2812B_Config_OC.OCNState = LL_TIM_OCSTATE_DISABLE;
	WS2812B_Config_OC.OCPolarity = LL_TIM_OCPOLARITY_HIGH;
	WS2812B_Config_OC.OCState = LL_TIM_OCSTATE_ENABLE;
	LL_TIM_OC_Init(TIM15, LL_TIM_CHANNEL_CH1, &WS2812B_Config_OC);
 
	WS2812B_Config_BDTR.AutomaticOutput = LL_TIM_AUTOMATICOUTPUT_DISABLE;
	WS2812B_Config_BDTR.Break2Filter = LL_TIM_BREAK2_FILTER_FDIV1;
	WS2812B_Config_BDTR.Break2Polarity = LL_TIM_BREAK2_POLARITY_LOW;
	WS2812B_Config_BDTR.Break2State = LL_TIM_BREAK2_DISABLE;
	WS2812B_Config_BDTR.BreakFilter = LL_TIM_BREAK_FILTER_FDIV1;
	WS2812B_Config_BDTR.BreakPolarity = LL_TIM_BREAK_POLARITY_LOW;
	WS2812B_Config_BDTR.BreakState = LL_TIM_BREAK_DISABLE;
	WS2812B_Config_BDTR.DeadTime = 0;
	WS2812B_Config_BDTR.LockLevel = LL_TIM_LOCKLEVEL_OFF;
	WS2812B_Config_BDTR.OSSIState = LL_TIM_OSSI_DISABLE;
	WS2812B_Config_BDTR.OSSRState = LL_TIM_OSSR_DISABLE;
	LL_TIM_BDTR_Init(TIM15, &WS2812B_Config_BDTR);
 
	LL_TIM_OC_EnablePreload(TIM15, LL_TIM_CHANNEL_CH1);
	LL_TIM_EnableARRPreload(TIM15);
	LL_TIM_EnableDMAReq_UPDATE(TIM15);
	LL_TIM_SetOnePulseMode(TIM15, LL_TIM_ONEPULSEMODE_SINGLE);
	LL_TIM_GenerateEvent_UPDATE(TIM15);
	LL_TIM_EnableAllOutputs(TIM15);

 Where TIM15 is enable. Essentially fill up the buffer before enabling the TIMER

void WS2812B::setColour(uint8_t GREEN, uint8_t RED, uint8_t BLUE) {
 
	for (uint32_t LED = 0; LED < NUM_LED; LED++) {
 
		for (int8_t G_bit = 7; G_bit >= 0; G_bit--) {
 
			if ((GREEN & (1<<(7 - G_bit)))) {
 
				WS28128B_BUFF[G_bit] = 0xC0;
			} else {
				WS28128B_BUFF[G_bit] = 0x60;
			}
		}
 
		for (int8_t R_bit = 15; R_bit >= 8; R_bit--) {
 
			if ((RED & (1<<(15 - R_bit)))) {
 
				WS28128B_BUFF[R_bit] = 0xC0;
			} else {
				WS28128B_BUFF[R_bit] = 0x60;
			}
		}
 
		for (int8_t B_bit = 23; B_bit >= 16; B_bit--) {
 
			if ((BLUE & (1<<(23 - B_bit)))) {
 
				WS28128B_BUFF[B_bit] = 0xC0;
			} else {
				WS28128B_BUFF[B_bit] = 0x60;
			}
		}
	}
 
	WS28128B_BUFF[(NUM_LED * 24)] = 0x2EE0;
	LL_DMA_EnableStream(DMA1, LL_DMA_STREAM_4);
	LL_TIM_EnableCounter(TIM15);
}