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Neopixel
Intro
https://en.wikipedia.org/wiki/Adafruit_Industries#NeoPixel
NeoPixel is Adafruit's brand of individually addressable red-green-blue (RGB) LED. They are based on the WS2812 LED and WS2811 driver, where the WS2811 is integrated into the LED, for reduced footprint. Adafruit manufactures several products with NeoPixels with form factors such as strips, rings, matrices, Arduino shields, traditional five-millimeter cylinder LED and individual NeoPixel with or without a PCB. The control protocol for NeoPixels is based on only one communication wire. How To UseSingle PixelThe Adafruit Feather STM32F405 Board has its own Neopixel (GPIO PC0, D8) :neopixel! ( rgb -- ) sets the neopixel RGB led ($ff0000 red, $00ff00 green, $0000ff blue)On the STM32WB Feather Development Board the NeoPixel shares the LED D12 pin. It is easy to add an Adafruit pixel breakout board or a Flora Pixel at the top of the shield. The LED can be used concurrently.
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< < | For the STM32WB Nucleo Board I use D6 for the Neopixel | ||||||||||||||||||||||||||
> > | For the STM32WB Nucleo Board I use D6 for the Neopixel. It takes about 30 us to set one Neopixel, during this time the interrupts are disabled. | ||||||||||||||||||||||||||
3 6 dmod \ D6 output $ff0000 neopixel! \ red LED 100 % brightness Neopixel Wing with 32 PixelsNeoPixelWing uses the D6 as datapin for the Neopixels:3 6 dmod \ D6 output 32 cells buffer: pixelbuffer \ create buffer for the neopixels $ff0000 pixelbuffer ! \ 1st Neopixel red $00ff00 pixelbuffer 1 cells + ! \ 2nd Neopixel green $0000ff pixelbuffer 2 cells + ! \ 3th Neopixel blue $7f7f7f pixelbuffer 3 cells + ! \ 4th Neopixel white 50 % pixelbuffer 4 neopixels create pixels $010000 , $020000 , $040000 , $080000 , $100000 , $200000 , $400000 , $800000 , \ 1st row red $008000 , $004000 , $002000 , $001000 , $000800 , $000400 , $000200 , $000100 , \ 2nd row green $000001 , $000002 , $000004 , $000008 , $000010 , $000020 , $000040 , $000080 , \ 3th row blue $808080 , $404040 , $202020 , $101010 , $080808 , $040404 , $020202 , $010101 , \ 4th row white pixels 32 neopixels | |||||||||||||||||||||||||||
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> > | It takes about 30 us to set one Neopixel, for 32 Pixels it takes nearly 1 ms, during this time the interrupts are disabled. Consider this for RT programs and interrupt latency. | ||||||||||||||||||||||||||
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ImplementationTimingWS2812B Neopixel
lsls r3, r3, #1 // set carry bit ittee cs movwcs r5, #T1H movtcs r5, #T1L movwcc r5, #T0H movtcc r5, #T0L6 cycles. HTML Color 0xRRGGBB F405https://github.com/spyren/Mecrisp-Cube/blob/F405/Forth/cube/wings.sCycle = 1 / 168 MHz = 6 ns 0.4 us / 6 ns = 66.7 -> max. 66 cycles .equ T0H, 16 // 0.3 us .equ T1H, 40 // 0.8 us .equ T0L, 36 // 0.8 us .equ T1L, 12 // 0.3 us WB55Cycle = 1 / 32 MHz = 31.25 ns 0.4 us / 31.25 ns = 12.8 -> max 12 cycles .equ T0H, 4 // 0.4 us / (3 * 31.25 ns) = 4.27 -> 4 .equ T1H, 8 // 0.8 us / (3 * 31.25 ns) = 8.53 -> 8 .equ T0L, 5 // 0.85 us / (3 * 31.25 ns) = 9.07 -> 5 (4 turns less) .equ T1L, 1 // 0.45 us / (3 * 31.25 ns) = 4.53 -> 1 (4 turns less) .equ RESTIME, 533 // 50 us / (3 * 31.25 ns) = 533 // Registers .equ GPIO_BSRR, 0x18 // GPIOx->BSRR bit set/reset .global BSP_neopixelDataTx BSP_neopixelDataTx: push {r4-r6, lr} lsl r2, r2, #8 // r2 = rrggbb00 mov r3, r2 // r3 = rrggbb00 bfc r3, #16, #16 // r3 = 0000bb00 rev16 r2, r2 // r2 = ggrr00bb bfc r2, #0, #16 // r2 = ggrr0000 add r2, r2, r3 // r2 = ggrrbb00 lsl r3, r1, #16 // clear port pin for BSRR mov r6, #24 // 24 bits // set DOUT pin low and wait reset time str r3, [r0, #GPIO_BSRR] ldr r4, =RESTIME 1: subs r4, r4, #1 1 bne 1b cycles bit_loop: lsls r2, r2, #1 // get the next bit -> set the carry bit 1 ittee cs 1 movcs r4, #T1H 1 movcs r5, #T1L 1 movcc r4, #T0H 1 movcc r5, #T0L 1 // set DOUT pin high str r1, [r0, #GPIO_BSRR] 2 1: subs r4, r4, #1 1 bne 1b 1 (2) // set DOUT pin low str r3, [r0, #GPIO_BSRR] 2 2: subs r5, r5, #1 1 bne 2b 1 (2) subs r6, r6, #1 1 bne bit_loop 2 pop {r4-r6, pc} Set/Reset PortpinGPIO port bit set/reset register GPIOx_BSRR
#define GPIOC_BASE (AHB1PERIPH_BASE + 0x0800UL) #define AHB1PERIPH_BASE (PERIPH_BASE + 0x00020000UL) #define PERIPH_BASE 0x40000000UL /*!< Peripheral base address in the alias region */ GPIOC->BSRR This work by Peter Schmid is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
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