Difference: NeoPixel (5 vs. 6)

Revision 62021-06-17 - PeterSchmid

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META TOPICPARENT	name="MecrispCubeF405"

NeoPixel

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WS2812B Neopixel

WS2812B data sheet https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf

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SK6812 https://cdn-shop.adafruit.com/product-files/1138/SK6812+LED+datasheet+.pdf

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T0H	0code, high voltage time	0.4us ±150ns
T1H	1code, high voltage time	0.8us ±150ns
T0L	0code, low voltage time	0.85us ±150ns
T1L	1code, low voltage time	0.45us ±150ns
RES	low voltage time	Above 50μs

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		WS2812B	SK6812
T0H	0 code, high voltage time	0.4 us ±150 ns	0.3 us ±150 ns
T1H	1 code, high voltage time	0.8 us ±150 ns	0.6 us ±150 ns
T0L	0 code, low voltage time	0.85 us ±150 ns	0.9 us ±150 ns
T1L	1 code, low voltage time	0.45 us ±150 ns	0.6 us ±150 ns
RES	low voltage time	Above 50 us	80 us

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1 bit takes 1.25 us, 24 bit take 30 us

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1 bit takes 1.25 us (800 kHz), 24 bit take 30 us

Timer resolution 0.25 us
MSB first
GRB

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3 cycles for a wait loop

Line: 35 to 38

HTML Color 0xRRGGBB

F405

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https://github.com/spyren/Mecrisp-Cube/blob/F405/Forth/cube/wings.s

Cycle = 1 / 168 MHz = 6 ns
0.4 us / 6 ns = 66.7 -> max. 66 cycles

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Timer Resolution = 1 / 42 MHz = 23.8 ns

#define T0H 15 // 0.4 us, 0.4 us / 23.8 ns = 16.8 #define T1H 32 // 0.8 us, 33.6 #define T0L 34 // 0.85 us, 35.7 #define T1L 17 // 0.45 us, 18.9 #define TRES 420 // 10 us, 420

max. deviation = timer_resolution + 2 cycles = 23.8 ns + 2 * 6 ns = 35.8 ns

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.equ T0H, 16 // 0.3 us .equ T1H, 40 // 0.8 us .equ T0L, 36 // 0.8 us .equ T1L, 12 // 0.3 us

WB55

Line: 55 to 54

Cycle = 1 / 32 MHz = 31.25 ns 0.4 us / 31.25 ns = 12.8 -> max 12 cycles

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Timer Resolution = 1 / 32 MHz = 31.25 ns

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#define T0H 11 // 0.4 us, 0.4 us / 31.25 ns = 12.8 #define T1H 24 // 0.8 us, 25.6 #define T0L 26 // 0.85 us, 27.4 #define T1L 13 // 0.45 us, 14.5 #define TRES 323 // 10 us, 323

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.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)

// 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

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}

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max. deviation = timer_resolution + 2 cycles = 31.25 ns ns + 2 * 31.25 ns = 93.75 ns

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Deleted:

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Timer

TIM6

Set Counter

TIM6->CNT;

Set Time Period

TIM6->ARR; // autoreload

Clear Update Flag

TIM6->SR; // UIF update interrupt flag

Enable/Disable Timer Interrupt

TIM6->DIER; // UIE update interrupt enable

Start/Stop Timer

TIM6->CR1; // UDIS update disable, CEN counter enable

META FILEATTACHMENT	attachment="timing-neopixel.png" attr="" comment="" date="1617633491" name="timing-neopixel.png" path="timing-neopixel.png" size="19590" user="PeterSchmid" version="1"

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