STM32用PWM +DMA驱动 WS2812 /* Buffer that holds one complete DMA transmission * * Ensure that this buffer is big enough to hold * all data bytes that need to be sent * * The buffer size can be calculated as follows: * number of LEDs * 24 bytes + 42 bytes * * This leaves us with a maximum string length of * (2^16 bytes per DMA stream - 42 bytes)/24 bytes per LED = 2728 LEDs