{"id":1060,"date":"2022-06-29T07:15:03","date_gmt":"2022-06-29T07:15:03","guid":{"rendered":"https:\/\/blog.embeddedexpert.io\/?p=1060"},"modified":"2022-06-29T07:29:28","modified_gmt":"2022-06-29T07:29:28","slug":"working-with-stm32-and-addressable-led-part-2-driver-development","status":"publish","type":"post","link":"https:\/\/blog.embeddedexpert.io\/?p=1060","title":{"rendered":"Working with STM32 and Addressable LED part 2: Driver development"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

In the pervious guide(here<\/a>), we took a look at the WS2812 and they work and type of communication required.<\/p>\n\n\n\n

In this guide, we shall see how to use PWM in DMA mode to control those LED.<\/p>\n\n\n\n

<\/p>\n\n\n\n

4. Setting up the PWM and DMA:<\/h2>\n\n\n\n

Since we shall use TIMER 1 of the STM32 to generate the required data signal, we shall develop everything around TIMER1.<\/p>\n\n\n\n

Since TIM1_CH1 is connected to PA8, we need to enable clock access to GPIOA and set PA8 to alternate function and select AF1 for PA8 as following:<\/p>\n\n\n\n

#define AF01   (0x01)\nRCC->AHB1ENR|=RCC_AHB1ENR_GPIOAEN;\nGPIOA->MODER|=GPIO_MODER_MODE8_1;\nGPIOA->MODER&=~GPIO_MODER_MODE8_0;\nGPIOA->AFR[1]|=(AF01<<0);<\/pre><\/div>\n\n\n\n
Then enable clock access to timer1<\/p>\n\n\n\n
RCC->APB2ENR|=RCC_APB2ENR_TIM1EN; \/\/enable clock access to tim1<\/pre><\/div>\n\n\n\n
Set the prescaler to 0:<\/p>\n\n\n\n
TIM1->PSC=0; \/\/set prescaller to 0 (no divider)<\/pre><\/div>\n\n\n\n
Set the ARR to 90 (maximum value to count):<\/p>\n\n\n\n
TIM1->ARR=90-1; \/\/set the maximum count value<\/pre><\/div>\n\n\n\n
Enable Capture\/Compare 1 DMA request:<\/p>\n\n\n\n
TIM1->DIER|=TIM_DIER_CC1DE;<\/pre><\/div>\n\n\n\n
Set CH1 as PWM mode and enable Output Compare 1 preload:<\/p>\n\n\n\n
TIM1->CCMR1|=TIM_CCMR1_OC1M_2|TIM_CCMR1_OC1M_1|TIM_CCMR1_OC1PE; \/\/configure the pin as PWM<\/pre><\/div>\n\n\n\n
Enable Capture\/Compare channel 1:<\/p>\n\n\n\n
TIM1->CCER|=TIM_CCER_CC1E; \/\/enable channel1<\/pre><\/div>\n\n\n\n
Set DMA address for full transfer to 1:<\/p>\n\n\n\n
TIM1->DMAR|=0x01;<\/pre><\/div>\n\n\n\n
Enable main output (For advanced timers only):<\/p>\n\n\n\n
TIM1->BDTR=TIM_BDTR_MOE;<\/pre><\/div>\n\n\n\n
<\/p>\n\n\n\n
Now, for DMA Setup.<\/p>\n\n\n\n
<\/p>\n\n\n\n
Since TIM1 is connected to DMA2 Stream1 Channel 6, we shall first enable clock access to DMA2 and disable the stream as following:<\/p>\n\n\n\n
RCC->AHB1ENR|=RCC_AHB1ENR_DMA2EN;\nDMA2_Stream1->CR&=~DMA_SxCR_EN;\nwhile((DMA2_Stream1->CR)&DMA_SxCR_EN){;}<\/pre><\/div>\n\n\n\n
Then we shall configure the DMA as following:<\/p>\n\n\n\n
  • Channel number 6<\/li>
  • Memory and peripheral 6 to half-word (16-bit)<\/li>
  • Memory Increment mode.<\/li>
  • Direct memory to peripheral.<\/li>
  • Transfer complete interrupt.<\/li><\/ul>\n\n\n\n
    #define CH6   ((0x06<<25))\nDMA2_Stream1->CR|=CH6|DMA_SxCR_MSIZE_0|DMA_SxCR_PSIZE_0|DMA_SxCR_MINC|DMA_SxCR_DIR_0|DMA_SxCR_TCIE;<\/pre><\/div>\n\n\n\n
    Set the peripheral address to TIM1->CCR1<\/p>\n\n\n\n
    DMA2_Stream1->PAR=(uint32_t)(&TIM1->CCR1);<\/pre><\/div>\n\n\n\n
    Enable DMA2_Stream1 interrupt in NVIC:<\/p>\n\n\n\n
    NVIC_EnableIRQ(DMA2_Stream1_IRQn);<\/pre><\/div>\n\n\n\n
    Hence, the initializing of PWM and DMA is as following:<\/p>\n\n\n\n
    void  WS2812_init(void){\n#define CH6   ((0x06<<25))\n#define AF01   (0x01)\n\/\/GPIO init\nRCC->AHB1ENR|=RCC_AHB1ENR_GPIOAEN;\nGPIOA->MODER|=GPIO_MODER_MODE8_1;\nGPIOA->MODER&=~GPIO_MODER_MODE8_0;\nGPIOA->AFR[1]|=(AF01<<0);\n\/\/init timer;\nRCC->APB2ENR|=RCC_APB2ENR_TIM1EN; \/\/enable clock access to tim1\nTIM1->PSC=0; \/\/set prescaller to 0 (no divider)\nTIM1->ARR=90-1; \/\/set the maximum count value\nTIM1->CNT=0; \/\/reset the current count\nTIM1->DIER|=TIM_DIER_CC1DE;\nTIM1->CCMR1|=TIM_CCMR1_OC1M_2|TIM_CCMR1_OC1M_1|TIM_CCMR1_OC1PE; \/\/configure the pin as PWM\nTIM1->CCER|=TIM_CCER_CC1E; \/\/enable channel1\nTIM1->DMAR|=0x01;\nTIM1->BDTR=TIM_BDTR_MOE;\n\n\/\/init dma\nRCC->AHB1ENR|=RCC_AHB1ENR_DMA2EN;\nDMA2_Stream1->CR&=~DMA_SxCR_EN;\nwhile((DMA2_Stream1->CR)&DMA_SxCR_EN){;}\nDMA2_Stream1->CR|=CH6|DMA_SxCR_MSIZE_0|DMA_SxCR_PSIZE_0|DMA_SxCR_MINC|DMA_SxCR_DIR_0|DMA_SxCR_TCIE;\nDMA2_Stream1->PAR=(uint32_t)(&TIM1->CCR1);\nNVIC_EnableIRQ(DMA2_Stream1_IRQn);\n}<\/pre><\/div>\n\n\n\n
    5. Setting up the LEDs:<\/h2>\n\n\n\n
    In this guide, we shall use LEDs ring which has 24 LEDs. Hence, we can create symbolic name for number of LEDs as following:<\/p>\n\n\n\n
    #define  Num_of_LEDs 24<\/pre><\/div>\n\n\n\n
    Then we shall create two two-dimensional arrays, one for GRB data and the other for brightness:<\/p>\n\n\n\n
    uint8_t LED_Data[Num_of_LEDs][4];\nuint8_t LED_Mod[Num_of_LEDs][4];  \/\/ for brightness<\/pre><\/div>\n\n\n\n
    Hence, the set led function is as following:<\/p>\n\n\n\n
    It takes four arguments:<\/p>\n\n\n\n