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alanburalanbur
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Add WS2811 RGB LED driver
Add include guard to arduino_pins.h Add ARRAYLEN macro to utils.h
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‎WS2811.h‎

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/*
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* Copyright 2012 Alan Burlison, alan@bleaklow.com. All rights reserved.
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* Use is subject to license terms.
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*/
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/*
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* WS2811 RGB LED driver.
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*/
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#ifndef WS2811_h
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#define WS2811_h
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// RGB value structure.
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typedef struct __attribute__ ((__packed__)) {
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uint8_t r;
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uint8_t g;
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uint8_t b;
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} RGB_t;
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#ifndef ARRAYLEN
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#define ARRAYLEN(A) (sizeof(A) / sizeof(A[0]))
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#endif
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/*
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* Inline asm macro to output 24-bit RGB value in (G,R,B) order, MSBit first.
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* 0 bits are 250ns hi, 1000ns lo, 1 bits are 1000ns hi, 250ns lo.
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* r18 = red byte to be output
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* r19 = green byte to be output
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* r20 = blue byte to be output
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* r26 = saved SREG
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* r27 = inner loop counter
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*/
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#define WS2811(PORT, PIN, RGB, LEN) \
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asm volatile( \
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/* initialise */ \
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" cp %A[len], r1 ; check len > 0, return immediately if it is\n" \
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" cpc %B[len], r1\n" \
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" brne 1f\n" \
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" rjmp 16f\n" \
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"1: ld r18, Z+ ; load in first red byte to be output\n" \
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" ld r19, Z+ ; load in first green byte to be output\n" \
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" ld r20, Z+ ; load in first blue byte to be output\n" \
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" ldi r27, 8 ; load inner loop counter\n" \
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" in r26, __SREG__ ; timing-critical, so no interrupts\n" \
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" cli\n" \
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/* green - loop over 8 bits */ \
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"2: sbi %[port], %[pin] ; pin lo -> hi\n" \
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" sbrc r19, 7 ; test hi bit clear\n" \
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" rjmp 3f ; true, skip pin hi -> lo\n" \
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" cbi %[port], %[pin] ; false, pin hi -> lo\n" \
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"3: sbrc r19, 7 ; equalise delay of both code paths\n" \
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" rjmp 4f\n" \
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"4: nop ; pulse timing delay\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" lsl r19 ; shift to next bit\n" \
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" dec r27 ; decrement loop counter\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" brne 2b\n ; loop if required\n" \
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" ldi r27, 7 ; reload inner loop counter\n" \
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/* red - loop over first 7 bits */ \
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"5: sbi %[port], %[pin] ; pin lo -> hi\n" \
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" sbrc r18, 7 ; test hi bit clear\n" \
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" rjmp 6f ; true, skip pin hi -> lo\n" \
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" cbi %[port], %[pin] ; false, pin hi -> lo\n" \
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"6: sbrc r18, 7 ; equalise delay of both code paths\n" \
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" rjmp 7f\n" \
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"7: nop ; pulse timing delay\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" lsl r18 ; shift to next bit\n" \
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" dec r27 ; decrement inner loop counter\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" brne 5b ; inner loop, if required\n" \
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" nop ; equalise delay of both code paths\n" \
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/* red, 8th bit - output & fetch next values */ \
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" sbi %[port], %[pin] ; pin lo -> hi\n" \
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" sbrc r18, 7 ; test hi bit clear\n" \
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" rjmp 8f ; true, skip pin hi -> lo\n" \
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" cbi %[port], %[pin] ; false, pin hi -> lo\n" \
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"8: sbrc r18, 7 ; equalise delay of both code paths\n" \
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" rjmp 9f\n" \
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"9: nop ; pulse timing delay\n" \
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" nop\n" \
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" nop\n" \
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" ld r18, Z+ ; load next red byte\n" \
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" ld r19, Z+ ; load next green byte\n" \
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" ldi r27, 7 ; reload inner loop counter\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" nop ; pulse timing delay\n" \
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" nop\n" \
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/* blue - loop over first 7 bits */ \
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"10: sbi %[port], %[pin] ; pin lo -> hi\n" \
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" sbrc r20, 7 ; test hi bit clear\n" \
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" rjmp 11f ; true, skip pin hi -> lo\n" \
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" cbi %[port], %[pin] ; false, pin hi -> lo\n" \
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"11: sbrc r20, 7 ; equalise delay of both code paths\n" \
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" rjmp 12f\n" \
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"12: nop ; pulse timing delay\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" nop\n" \
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" lsl r20 ; shift to next bit\n" \
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" dec r27 ; decrement inner loop counter\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" brne 10b ; inner loop, if required\n" \
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" nop ; equalise delay of both code paths\n" \
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/* blue, 8th bit - output & handle outer loop */ \
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" sbi %[port], %[pin] ; pin lo -> hi\n" \
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" sbrc r20, 7 ; test hi bit clear\n" \
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" rjmp 13f ; true, skip pin hi -> lo\n" \
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" cbi %[port], %[pin] ; false, pin hi -> lo\n" \
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"13: sbrc r20, 7 ; equalise delay of both code paths\n" \
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" rjmp 14f\n" \
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"14: nop ; pulse timing delay\n" \
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" nop\n" \
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" ldi r27, 8 ; reload inner loop counter\n" \
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" sbiw %A[len], 1 ; decrement outer loop counter\n" \
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" breq 15f ; exit outer loop if zero\n" \
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" ld r20, Z+ ; load in next blue byte\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" rjmp 2b ; outer loop, if required\n" \
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"15: nop ; pulse timing delay\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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" nop ; pulse timing delay\n" \
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" nop\n" \
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" out __SREG__, r26 ; reenable interrupts\n" \
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"16:\n" \
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" sbi %[port], %[pin] ; pin hi -> lo\n" \
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" cbi %[port], %[pin] ; pin hi -> lo\n" \
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: \
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: [rgb] "z" (RGB), \
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[len] "w" (LEN), \
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[port] "I" (_SFR_IO_ADDR(PORT)), \
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[pin] "I" (PIN) \
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: "r18", "r19", "r20", "r26", "r27", "cc", "memory" \
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)
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/*
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* Define a C function to wrap the inline WS2811 macro for a given port and pin.
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*/
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#define DEFINE_WS2811_FN(NAME, PORT, PIN) \
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extern void NAME(const RGB_t *rgb, uint16_t len) __attribute__((noinline)); \
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void NAME(const RGB_t *rgb, uint16_t len) { WS2811(PORT, PIN, rgb, len); }
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#endif /* WS2811_h */

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