-
Notifications
You must be signed in to change notification settings - Fork 0
/
Adafruit_NeoPixel.cpp
1029 lines (924 loc) · 39.6 KB
/
Adafruit_NeoPixel.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/*-------------------------------------------------------------------------
Arduino library to control a wide variety of WS2811- and WS2812-based RGB
LED devices such as Adafruit FLORA RGB Smart Pixels and NeoPixel strips.
Currently handles 400 and 800 KHz bitstreams on 8, 12 and 16 MHz ATmega
MCUs, with LEDs wired for RGB or GRB color order. 8 MHz MCUs provide
output on PORTB and PORTD, while 16 MHz chips can handle most output pins
(possible exception with upper PORT registers on the Arduino Mega).
Written by Phil Burgess / Paint Your Dragon for Adafruit Industries,
contributions by PJRC and other members of the open source community.
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing products
from Adafruit!
-------------------------------------------------------------------------
This file is part of the Adafruit NeoPixel library.
NeoPixel is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation, either version 3 of
the License, or (at your option) any later version.
NeoPixel is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with NeoPixel. If not, see
<http://www.gnu.org/licenses/>.
-------------------------------------------------------------------------*/
#include "Adafruit_NeoPixel.h"
Adafruit_NeoPixel::Adafruit_NeoPixel(uint16_t n, uint8_t p, uint8_t t) :
numLEDs(n), numBytes(n * 3), pin(p), brightness(0),
pixels(NULL), type(t), endTime(0)
#ifdef __AVR__
,port(portOutputRegister(digitalPinToPort(p))),
pinMask(digitalPinToBitMask(p))
#endif
{
if((pixels = (uint8_t *)malloc(numBytes))) {
memset(pixels, 0, numBytes);
}
if(t & NEO_GRB) { // GRB vs RGB; might add others if needed
rOffset = 1;
gOffset = 0;
bOffset = 2;
} else if (t & NEO_BRG) {
rOffset = 1;
gOffset = 2;
bOffset = 0;
} else {
rOffset = 0;
gOffset = 1;
bOffset = 2;
}
}
Adafruit_NeoPixel::~Adafruit_NeoPixel() {
if(pixels) free(pixels);
pinMode(pin, INPUT);
}
void Adafruit_NeoPixel::begin(void) {
pinMode(pin, OUTPUT);
digitalWrite(pin, LOW);
}
void Adafruit_NeoPixel::show(void) {
if(!pixels) return;
// Data latch = 50+ microsecond pause in the output stream. Rather than
// put a delay at the end of the function, the ending time is noted and
// the function will simply hold off (if needed) on issuing the
// subsequent round of data until the latch time has elapsed. This
// allows the mainline code to start generating the next frame of data
// rather than stalling for the latch.
while(!canShow());
// endTime is a private member (rather than global var) so that mutliple
// instances on different pins can be quickly issued in succession (each
// instance doesn't delay the next).
// In order to make this code runtime-configurable to work with any pin,
// SBI/CBI instructions are eschewed in favor of full PORT writes via the
// OUT or ST instructions. It relies on two facts: that peripheral
// functions (such as PWM) take precedence on output pins, so our PORT-
// wide writes won't interfere, and that interrupts are globally disabled
// while data is being issued to the LEDs, so no other code will be
// accessing the PORT. The code takes an initial 'snapshot' of the PORT
// state, computes 'pin high' and 'pin low' values, and writes these back
// to the PORT register as needed.
noInterrupts(); // Need 100% focus on instruction timing
#ifdef __AVR__
volatile uint16_t
i = numBytes; // Loop counter
volatile uint8_t
*ptr = pixels, // Pointer to next byte
b = *ptr++, // Current byte value
hi, // PORT w/output bit set high
lo; // PORT w/output bit set low
// Hand-tuned assembly code issues data to the LED drivers at a specific
// rate. There's separate code for different CPU speeds (8, 12, 16 MHz)
// for both the WS2811 (400 KHz) and WS2812 (800 KHz) drivers. The
// datastream timing for the LED drivers allows a little wiggle room each
// way (listed in the datasheets), so the conditions for compiling each
// case are set up for a range of frequencies rather than just the exact
// 8, 12 or 16 MHz values, permitting use with some close-but-not-spot-on
// devices (e.g. 16.5 MHz DigiSpark). The ranges were arrived at based
// on the datasheet figures and have not been extensively tested outside
// the canonical 8/12/16 MHz speeds; there's no guarantee these will work
// close to the extremes (or possibly they could be pushed further).
// Keep in mind only one CPU speed case actually gets compiled; the
// resulting program isn't as massive as it might look from source here.
// 8 MHz(ish) AVR ---------------------------------------------------------
#if (F_CPU >= 7400000UL) && (F_CPU <= 9500000UL)
#ifdef NEO_KHZ400
if((type & NEO_SPDMASK) == NEO_KHZ800) { // 800 KHz bitstream
#endif
volatile uint8_t n1, n2 = 0; // First, next bits out
// Squeezing an 800 KHz stream out of an 8 MHz chip requires code
// specific to each PORT register. At present this is only written
// to work with pins on PORTD or PORTB, the most likely use case --
// this covers all the pins on the Adafruit Flora and the bulk of
// digital pins on the Arduino Pro 8 MHz (keep in mind, this code
// doesn't even get compiled for 16 MHz boards like the Uno, Mega,
// Leonardo, etc., so don't bother extending this out of hand).
// Additional PORTs could be added if you really need them, just
// duplicate the else and loop and change the PORT. Each add'l
// PORT will require about 150(ish) bytes of program space.
// 10 instruction clocks per bit: HHxxxxxLLL
// OUT instructions: ^ ^ ^ (T=0,2,7)
#ifdef PORTD // PORTD isn't present on ATtiny85, etc.
if(port == &PORTD) {
hi = PORTD | pinMask;
lo = PORTD & ~pinMask;
n1 = lo;
if(b & 0x80) n1 = hi;
// Dirty trick: RJMPs proceeding to the next instruction are used
// to delay two clock cycles in one instruction word (rather than
// using two NOPs). This was necessary in order to squeeze the
// loop down to exactly 64 words -- the maximum possible for a
// relative branch.
asm volatile(
"headD:" "\n\t" // Clk Pseudocode
// Bit 7:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n2] , %[lo]" "\n\t" // 1 n2 = lo
"out %[port] , %[n1]" "\n\t" // 1 PORT = n1
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 6" "\n\t" // 1-2 if(b & 0x40)
"mov %[n2] , %[hi]" "\n\t" // 0-1 n2 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 6:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n1] , %[lo]" "\n\t" // 1 n1 = lo
"out %[port] , %[n2]" "\n\t" // 1 PORT = n2
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 5" "\n\t" // 1-2 if(b & 0x20)
"mov %[n1] , %[hi]" "\n\t" // 0-1 n1 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 5:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n2] , %[lo]" "\n\t" // 1 n2 = lo
"out %[port] , %[n1]" "\n\t" // 1 PORT = n1
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 4" "\n\t" // 1-2 if(b & 0x10)
"mov %[n2] , %[hi]" "\n\t" // 0-1 n2 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 4:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n1] , %[lo]" "\n\t" // 1 n1 = lo
"out %[port] , %[n2]" "\n\t" // 1 PORT = n2
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 3" "\n\t" // 1-2 if(b & 0x08)
"mov %[n1] , %[hi]" "\n\t" // 0-1 n1 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 3:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n2] , %[lo]" "\n\t" // 1 n2 = lo
"out %[port] , %[n1]" "\n\t" // 1 PORT = n1
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 2" "\n\t" // 1-2 if(b & 0x04)
"mov %[n2] , %[hi]" "\n\t" // 0-1 n2 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 2:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n1] , %[lo]" "\n\t" // 1 n1 = lo
"out %[port] , %[n2]" "\n\t" // 1 PORT = n2
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 1" "\n\t" // 1-2 if(b & 0x02)
"mov %[n1] , %[hi]" "\n\t" // 0-1 n1 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"rjmp .+0" "\n\t" // 2 nop nop
// Bit 1:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n2] , %[lo]" "\n\t" // 1 n2 = lo
"out %[port] , %[n1]" "\n\t" // 1 PORT = n1
"rjmp .+0" "\n\t" // 2 nop nop
"sbrc %[byte] , 0" "\n\t" // 1-2 if(b & 0x01)
"mov %[n2] , %[hi]" "\n\t" // 0-1 n2 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"sbiw %[count], 1" "\n\t" // 2 i-- (don't act on Z flag yet)
// Bit 0:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi
"mov %[n1] , %[lo]" "\n\t" // 1 n1 = lo
"out %[port] , %[n2]" "\n\t" // 1 PORT = n2
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++
"sbrc %[byte] , 7" "\n\t" // 1-2 if(b & 0x80)
"mov %[n1] , %[hi]" "\n\t" // 0-1 n1 = hi
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo
"brne headD" "\n" // 2 while(i) (Z flag set above)
: [byte] "+r" (b),
[n1] "+r" (n1),
[n2] "+r" (n2),
[count] "+w" (i)
: [port] "I" (_SFR_IO_ADDR(PORTD)),
[ptr] "e" (ptr),
[hi] "r" (hi),
[lo] "r" (lo));
} else if(port == &PORTB) {
#endif // PORTD
// Same as above, just switched to PORTB and stripped of comments.
hi = PORTB | pinMask;
lo = PORTB & ~pinMask;
n1 = lo;
if(b & 0x80) n1 = hi;
asm volatile(
"headB:" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n2] , %[lo]" "\n\t"
"out %[port] , %[n1]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 6" "\n\t"
"mov %[n2] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n1] , %[lo]" "\n\t"
"out %[port] , %[n2]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 5" "\n\t"
"mov %[n1] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n2] , %[lo]" "\n\t"
"out %[port] , %[n1]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 4" "\n\t"
"mov %[n2] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n1] , %[lo]" "\n\t"
"out %[port] , %[n2]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 3" "\n\t"
"mov %[n1] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n2] , %[lo]" "\n\t"
"out %[port] , %[n1]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 2" "\n\t"
"mov %[n2] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n1] , %[lo]" "\n\t"
"out %[port] , %[n2]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 1" "\n\t"
"mov %[n1] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"rjmp .+0" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n2] , %[lo]" "\n\t"
"out %[port] , %[n1]" "\n\t"
"rjmp .+0" "\n\t"
"sbrc %[byte] , 0" "\n\t"
"mov %[n2] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"sbiw %[count], 1" "\n\t"
"out %[port] , %[hi]" "\n\t"
"mov %[n1] , %[lo]" "\n\t"
"out %[port] , %[n2]" "\n\t"
"ld %[byte] , %a[ptr]+" "\n\t"
"sbrc %[byte] , 7" "\n\t"
"mov %[n1] , %[hi]" "\n\t"
"out %[port] , %[lo]" "\n\t"
"brne headB" "\n"
: [byte] "+r" (b), [n1] "+r" (n1), [n2] "+r" (n2), [count] "+w" (i)
: [port] "I" (_SFR_IO_ADDR(PORTB)), [ptr] "e" (ptr), [hi] "r" (hi),
[lo] "r" (lo));
#ifdef PORTD
} // endif PORTB
#endif
#ifdef NEO_KHZ400
} else { // end 800 KHz, do 400 KHz
// Timing is more relaxed; unrolling the inner loop for each bit is
// not necessary. Still using the peculiar RJMPs as 2X NOPs, not out
// of need but just to trim the code size down a little.
// This 400-KHz-datastream-on-8-MHz-CPU code is not quite identical
// to the 800-on-16 code later -- the hi/lo timing between WS2811 and
// WS2812 is not simply a 2:1 scale!
// 20 inst. clocks per bit: HHHHxxxxxxLLLLLLLLLL
// ST instructions: ^ ^ ^ (T=0,4,10)
volatile uint8_t next, bit;
hi = *port | pinMask;
lo = *port & ~pinMask;
next = lo;
bit = 8;
asm volatile(
"head20:" "\n\t" // Clk Pseudocode (T = 0)
"st %a[port], %[hi]" "\n\t" // 2 PORT = hi (T = 2)
"sbrc %[byte] , 7" "\n\t" // 1-2 if(b & 128)
"mov %[next], %[hi]" "\n\t" // 0-1 next = hi (T = 4)
"st %a[port], %[next]" "\n\t" // 2 PORT = next (T = 6)
"mov %[next] , %[lo]" "\n\t" // 1 next = lo (T = 7)
"dec %[bit]" "\n\t" // 1 bit-- (T = 8)
"breq nextbyte20" "\n\t" // 1-2 if(bit == 0)
"rol %[byte]" "\n\t" // 1 b <<= 1 (T = 10)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 12)
"rjmp .+0" "\n\t" // 2 nop nop (T = 14)
"rjmp .+0" "\n\t" // 2 nop nop (T = 16)
"rjmp .+0" "\n\t" // 2 nop nop (T = 18)
"rjmp head20" "\n\t" // 2 -> head20 (next bit out)
"nextbyte20:" "\n\t" // (T = 10)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 12)
"nop" "\n\t" // 1 nop (T = 13)
"ldi %[bit] , 8" "\n\t" // 1 bit = 8 (T = 14)
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++ (T = 16)
"sbiw %[count], 1" "\n\t" // 2 i-- (T = 18)
"brne head20" "\n" // 2 if(i != 0) -> (next byte)
: [port] "+e" (port),
[byte] "+r" (b),
[bit] "+r" (bit),
[next] "+r" (next),
[count] "+w" (i)
: [hi] "r" (hi),
[lo] "r" (lo),
[ptr] "e" (ptr));
}
#endif
// 12 MHz(ish) AVR --------------------------------------------------------
#elif (F_CPU >= 11100000UL) && (F_CPU <= 14300000UL)
#ifdef NEO_KHZ400
if((type & NEO_SPDMASK) == NEO_KHZ800) { // 800 KHz bitstream
#endif
// In the 12 MHz case, an optimized 800 KHz datastream (no dead time
// between bytes) requires a PORT-specific loop similar to the 8 MHz
// code (but a little more relaxed in this case).
// 15 instruction clocks per bit: HHHHxxxxxxLLLLL
// OUT instructions: ^ ^ ^ (T=0,4,10)
volatile uint8_t next;
#ifdef PORTD
if(port == &PORTD) {
hi = PORTD | pinMask;
lo = PORTD & ~pinMask;
next = lo;
if(b & 0x80) next = hi;
// Don't "optimize" the OUT calls into the bitTime subroutine;
// we're exploiting the RCALL and RET as 3- and 4-cycle NOPs!
asm volatile(
"headD:" "\n\t" // (T = 0)
"out %[port], %[hi]" "\n\t" // (T = 1)
"rcall bitTimeD" "\n\t" // Bit 7 (T = 15)
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 6
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 5
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 4
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 3
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 2
"out %[port], %[hi]" "\n\t"
"rcall bitTimeD" "\n\t" // Bit 1
// Bit 0:
"out %[port] , %[hi]" "\n\t" // 1 PORT = hi (T = 1)
"rjmp .+0" "\n\t" // 2 nop nop (T = 3)
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++ (T = 5)
"out %[port] , %[next]" "\n\t" // 1 PORT = next (T = 6)
"mov %[next] , %[lo]" "\n\t" // 1 next = lo (T = 7)
"sbrc %[byte] , 7" "\n\t" // 1-2 if(b & 0x80) (T = 8)
"mov %[next] , %[hi]" "\n\t" // 0-1 next = hi (T = 9)
"nop" "\n\t" // 1 (T = 10)
"out %[port] , %[lo]" "\n\t" // 1 PORT = lo (T = 11)
"sbiw %[count], 1" "\n\t" // 2 i-- (T = 13)
"brne headD" "\n\t" // 2 if(i != 0) -> (next byte)
"rjmp doneD" "\n\t"
"bitTimeD:" "\n\t" // nop nop nop (T = 4)
"out %[port], %[next]" "\n\t" // 1 PORT = next (T = 5)
"mov %[next], %[lo]" "\n\t" // 1 next = lo (T = 6)
"rol %[byte]" "\n\t" // 1 b <<= 1 (T = 7)
"sbrc %[byte], 7" "\n\t" // 1-2 if(b & 0x80) (T = 8)
"mov %[next], %[hi]" "\n\t" // 0-1 next = hi (T = 9)
"nop" "\n\t" // 1 (T = 10)
"out %[port], %[lo]" "\n\t" // 1 PORT = lo (T = 11)
"ret" "\n\t" // 4 nop nop nop nop (T = 15)
"doneD:" "\n"
: [byte] "+r" (b),
[next] "+r" (next),
[count] "+w" (i)
: [port] "I" (_SFR_IO_ADDR(PORTD)),
[ptr] "e" (ptr),
[hi] "r" (hi),
[lo] "r" (lo));
} else if(port == &PORTB) {
#endif // PORTD
hi = PORTB | pinMask;
lo = PORTB & ~pinMask;
next = lo;
if(b & 0x80) next = hi;
// Same as above, just set for PORTB & stripped of comments
asm volatile(
"headB:" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port], %[hi]" "\n\t"
"rcall bitTimeB" "\n\t"
"out %[port] , %[hi]" "\n\t"
"rjmp .+0" "\n\t"
"ld %[byte] , %a[ptr]+" "\n\t"
"out %[port] , %[next]" "\n\t"
"mov %[next] , %[lo]" "\n\t"
"sbrc %[byte] , 7" "\n\t"
"mov %[next] , %[hi]" "\n\t"
"nop" "\n\t"
"out %[port] , %[lo]" "\n\t"
"sbiw %[count], 1" "\n\t"
"brne headB" "\n\t"
"rjmp doneB" "\n\t"
"bitTimeB:" "\n\t"
"out %[port], %[next]" "\n\t"
"mov %[next], %[lo]" "\n\t"
"rol %[byte]" "\n\t"
"sbrc %[byte], 7" "\n\t"
"mov %[next], %[hi]" "\n\t"
"nop" "\n\t"
"out %[port], %[lo]" "\n\t"
"ret" "\n\t"
"doneB:" "\n"
: [byte] "+r" (b), [next] "+r" (next), [count] "+w" (i)
: [port] "I" (_SFR_IO_ADDR(PORTB)), [ptr] "e" (ptr), [hi] "r" (hi),
[lo] "r" (lo));
#ifdef PORTD
}
#endif
#ifdef NEO_KHZ400
} else { // 400 KHz
// 30 instruction clocks per bit: HHHHHHxxxxxxxxxLLLLLLLLLLLLLLL
// ST instructions: ^ ^ ^ (T=0,6,15)
volatile uint8_t next, bit;
hi = *port | pinMask;
lo = *port & ~pinMask;
next = lo;
bit = 8;
asm volatile(
"head30:" "\n\t" // Clk Pseudocode (T = 0)
"st %a[port], %[hi]" "\n\t" // 2 PORT = hi (T = 2)
"sbrc %[byte] , 7" "\n\t" // 1-2 if(b & 128)
"mov %[next], %[hi]" "\n\t" // 0-1 next = hi (T = 4)
"rjmp .+0" "\n\t" // 2 nop nop (T = 6)
"st %a[port], %[next]" "\n\t" // 2 PORT = next (T = 8)
"rjmp .+0" "\n\t" // 2 nop nop (T = 10)
"rjmp .+0" "\n\t" // 2 nop nop (T = 12)
"rjmp .+0" "\n\t" // 2 nop nop (T = 14)
"nop" "\n\t" // 1 nop (T = 15)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 17)
"rjmp .+0" "\n\t" // 2 nop nop (T = 19)
"dec %[bit]" "\n\t" // 1 bit-- (T = 20)
"breq nextbyte30" "\n\t" // 1-2 if(bit == 0)
"rol %[byte]" "\n\t" // 1 b <<= 1 (T = 22)
"rjmp .+0" "\n\t" // 2 nop nop (T = 24)
"rjmp .+0" "\n\t" // 2 nop nop (T = 26)
"rjmp .+0" "\n\t" // 2 nop nop (T = 28)
"rjmp head30" "\n\t" // 2 -> head30 (next bit out)
"nextbyte30:" "\n\t" // (T = 22)
"nop" "\n\t" // 1 nop (T = 23)
"ldi %[bit] , 8" "\n\t" // 1 bit = 8 (T = 24)
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++ (T = 26)
"sbiw %[count], 1" "\n\t" // 2 i-- (T = 28)
"brne head30" "\n" // 1-2 if(i != 0) -> (next byte)
: [port] "+e" (port),
[byte] "+r" (b),
[bit] "+r" (bit),
[next] "+r" (next),
[count] "+w" (i)
: [hi] "r" (hi),
[lo] "r" (lo),
[ptr] "e" (ptr));
}
#endif
// 16 MHz(ish) AVR --------------------------------------------------------
#elif (F_CPU >= 15400000UL) && (F_CPU <= 19000000L)
#ifdef NEO_KHZ400
if((type & NEO_SPDMASK) == NEO_KHZ800) { // 800 KHz bitstream
#endif
// WS2811 and WS2812 have different hi/lo duty cycles; this is
// similar but NOT an exact copy of the prior 400-on-8 code.
// 20 inst. clocks per bit: HHHHHxxxxxxxxLLLLLLL
// ST instructions: ^ ^ ^ (T=0,5,13)
volatile uint8_t next, bit;
hi = *port | pinMask;
lo = *port & ~pinMask;
next = lo;
bit = 8;
asm volatile(
"head20:" "\n\t" // Clk Pseudocode (T = 0)
"st %a[port], %[hi]" "\n\t" // 2 PORT = hi (T = 2)
"sbrc %[byte], 7" "\n\t" // 1-2 if(b & 128)
"mov %[next], %[hi]" "\n\t" // 0-1 next = hi (T = 4)
"dec %[bit]" "\n\t" // 1 bit-- (T = 5)
"st %a[port], %[next]" "\n\t" // 2 PORT = next (T = 7)
"mov %[next] , %[lo]" "\n\t" // 1 next = lo (T = 8)
"breq nextbyte20" "\n\t" // 1-2 if(bit == 0) (from dec above)
"rol %[byte]" "\n\t" // 1 b <<= 1 (T = 10)
"rjmp .+0" "\n\t" // 2 nop nop (T = 12)
"nop" "\n\t" // 1 nop (T = 13)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 15)
"nop" "\n\t" // 1 nop (T = 16)
"rjmp .+0" "\n\t" // 2 nop nop (T = 18)
"rjmp head20" "\n\t" // 2 -> head20 (next bit out)
"nextbyte20:" "\n\t" // (T = 10)
"ldi %[bit] , 8" "\n\t" // 1 bit = 8 (T = 11)
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++ (T = 13)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 15)
"nop" "\n\t" // 1 nop (T = 16)
"sbiw %[count], 1" "\n\t" // 2 i-- (T = 18)
"brne head20" "\n" // 2 if(i != 0) -> (next byte)
: [port] "+e" (port),
[byte] "+r" (b),
[bit] "+r" (bit),
[next] "+r" (next),
[count] "+w" (i)
: [ptr] "e" (ptr),
[hi] "r" (hi),
[lo] "r" (lo));
#ifdef NEO_KHZ400
} else { // 400 KHz
// The 400 KHz clock on 16 MHz MCU is the most 'relaxed' version.
// 40 inst. clocks per bit: HHHHHHHHxxxxxxxxxxxxLLLLLLLLLLLLLLLLLLLL
// ST instructions: ^ ^ ^ (T=0,8,20)
volatile uint8_t next, bit;
hi = *port | pinMask;
lo = *port & ~pinMask;
next = lo;
bit = 8;
asm volatile(
"head40:" "\n\t" // Clk Pseudocode (T = 0)
"st %a[port], %[hi]" "\n\t" // 2 PORT = hi (T = 2)
"sbrc %[byte] , 7" "\n\t" // 1-2 if(b & 128)
"mov %[next] , %[hi]" "\n\t" // 0-1 next = hi (T = 4)
"rjmp .+0" "\n\t" // 2 nop nop (T = 6)
"rjmp .+0" "\n\t" // 2 nop nop (T = 8)
"st %a[port], %[next]" "\n\t" // 2 PORT = next (T = 10)
"rjmp .+0" "\n\t" // 2 nop nop (T = 12)
"rjmp .+0" "\n\t" // 2 nop nop (T = 14)
"rjmp .+0" "\n\t" // 2 nop nop (T = 16)
"rjmp .+0" "\n\t" // 2 nop nop (T = 18)
"rjmp .+0" "\n\t" // 2 nop nop (T = 20)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 22)
"nop" "\n\t" // 1 nop (T = 23)
"mov %[next] , %[lo]" "\n\t" // 1 next = lo (T = 24)
"dec %[bit]" "\n\t" // 1 bit-- (T = 25)
"breq nextbyte40" "\n\t" // 1-2 if(bit == 0)
"rol %[byte]" "\n\t" // 1 b <<= 1 (T = 27)
"nop" "\n\t" // 1 nop (T = 28)
"rjmp .+0" "\n\t" // 2 nop nop (T = 30)
"rjmp .+0" "\n\t" // 2 nop nop (T = 32)
"rjmp .+0" "\n\t" // 2 nop nop (T = 34)
"rjmp .+0" "\n\t" // 2 nop nop (T = 36)
"rjmp .+0" "\n\t" // 2 nop nop (T = 38)
"rjmp head40" "\n\t" // 2 -> head40 (next bit out)
"nextbyte40:" "\n\t" // (T = 27)
"ldi %[bit] , 8" "\n\t" // 1 bit = 8 (T = 28)
"ld %[byte] , %a[ptr]+" "\n\t" // 2 b = *ptr++ (T = 30)
"rjmp .+0" "\n\t" // 2 nop nop (T = 32)
"st %a[port], %[lo]" "\n\t" // 2 PORT = lo (T = 34)
"rjmp .+0" "\n\t" // 2 nop nop (T = 36)
"sbiw %[count], 1" "\n\t" // 2 i-- (T = 38)
"brne head40" "\n" // 1-2 if(i != 0) -> (next byte)
: [port] "+e" (port),
[byte] "+r" (b),
[bit] "+r" (bit),
[next] "+r" (next),
[count] "+w" (i)
: [ptr] "e" (ptr),
[hi] "r" (hi),
[lo] "r" (lo));
}
#endif
#else
#error "CPU SPEED NOT SUPPORTED"
#endif
#elif defined(__arm__)
#if defined(__MK20DX128__) || defined(__MK20DX256__) // Teensy 3.0 & 3.1
#define CYCLES_800_T0H (F_CPU / 4000000)
#define CYCLES_800_T1H (F_CPU / 1250000)
#define CYCLES_800 (F_CPU / 800000)
#define CYCLES_400_T0H (F_CPU / 2000000)
#define CYCLES_400_T1H (F_CPU / 833333)
#define CYCLES_400 (F_CPU / 400000)
uint8_t *p = pixels,
*end = p + numBytes, pix, mask;
volatile uint8_t *set = portSetRegister(pin),
*clr = portClearRegister(pin);
uint32_t cyc;
ARM_DEMCR |= ARM_DEMCR_TRCENA;
ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA;
#ifdef NEO_KHZ400
if((type & NEO_SPDMASK) == NEO_KHZ800) { // 800 KHz bitstream
#endif
cyc = ARM_DWT_CYCCNT + CYCLES_800;
while(p < end) {
pix = *p++;
for(mask = 0x80; mask; mask >>= 1) {
while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
cyc = ARM_DWT_CYCCNT;
*set = 1;
if(pix & mask) {
while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T1H);
} else {
while(ARM_DWT_CYCCNT - cyc < CYCLES_800_T0H);
}
*clr = 1;
}
}
while(ARM_DWT_CYCCNT - cyc < CYCLES_800);
#ifdef NEO_KHZ400
} else { // 400 kHz bitstream
cyc = ARM_DWT_CYCCNT + CYCLES_400;
while(p < end) {
pix = *p++;
for(mask = 0x80; mask; mask >>= 1) {
while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
cyc = ARM_DWT_CYCCNT;
*set = 1;
if(pix & mask) {
while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T1H);
} else {
while(ARM_DWT_CYCCNT - cyc < CYCLES_400_T0H);
}
*clr = 1;
}
}
while(ARM_DWT_CYCCNT - cyc < CYCLES_400);
}
#endif
#elif defined(__MKL26Z64__) // Teensy-LC
#if F_CPU == 48000000
uint8_t *p = pixels,
pix, count, dly,
bitmask = digitalPinToBitMask(pin);
volatile uint8_t *reg = portSetRegister(pin);
uint32_t num = numBytes;
asm volatile(
"L%=_begin:" "\n\t"
"ldrb %[pix], [%[p], #0]" "\n\t"
"lsl %[pix], #24" "\n\t"
"movs %[count], #7" "\n\t"
"L%=_loop:" "\n\t"
"lsl %[pix], #1" "\n\t"
"bcs L%=_loop_one" "\n\t"
"L%=_loop_zero:"
"strb %[bitmask], [%[reg], #0]" "\n\t"
"movs %[dly], #4" "\n\t"
"L%=_loop_delay_T0H:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_loop_delay_T0H" "\n\t"
"strb %[bitmask], [%[reg], #4]" "\n\t"
"movs %[dly], #13" "\n\t"
"L%=_loop_delay_T0L:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_loop_delay_T0L" "\n\t"
"b L%=_next" "\n\t"
"L%=_loop_one:"
"strb %[bitmask], [%[reg], #0]" "\n\t"
"movs %[dly], #13" "\n\t"
"L%=_loop_delay_T1H:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_loop_delay_T1H" "\n\t"
"strb %[bitmask], [%[reg], #4]" "\n\t"
"movs %[dly], #4" "\n\t"
"L%=_loop_delay_T1L:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_loop_delay_T1L" "\n\t"
"nop" "\n\t"
"L%=_next:" "\n\t"
"sub %[count], #1" "\n\t"
"bne L%=_loop" "\n\t"
"lsl %[pix], #1" "\n\t"
"bcs L%=_last_one" "\n\t"
"L%=_last_zero:"
"strb %[bitmask], [%[reg], #0]" "\n\t"
"movs %[dly], #4" "\n\t"
"L%=_last_delay_T0H:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_last_delay_T0H" "\n\t"
"strb %[bitmask], [%[reg], #4]" "\n\t"
"movs %[dly], #10" "\n\t"
"L%=_last_delay_T0L:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_last_delay_T0L" "\n\t"
"b L%=_repeat" "\n\t"
"L%=_last_one:"
"strb %[bitmask], [%[reg], #0]" "\n\t"
"movs %[dly], #13" "\n\t"
"L%=_last_delay_T1H:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_last_delay_T1H" "\n\t"
"strb %[bitmask], [%[reg], #4]" "\n\t"
"movs %[dly], #1" "\n\t"
"L%=_last_delay_T1L:" "\n\t"
"sub %[dly], #1" "\n\t"
"bne L%=_last_delay_T1L" "\n\t"
"nop" "\n\t"
"L%=_repeat:" "\n\t"
"add %[p], #1" "\n\t"
"sub %[num], #1" "\n\t"
"bne L%=_begin" "\n\t"
"L%=_done:" "\n\t"
: [p] "+r" (p),
[pix] "=&r" (pix),
[count] "=&r" (count),
[dly] "=&r" (dly),
[num] "+r" (num)
: [bitmask] "r" (bitmask),
[reg] "r" (reg)
);
#else
#error "Sorry, only 48 MHz is supported, please set Tools > CPU Speed to 48 MHz"
#endif
#else // Arduino Due
#define SCALE VARIANT_MCK / 2UL / 1000000UL
#define INST (2UL * F_CPU / VARIANT_MCK)
#define TIME_800_0 ((int)(0.40 * SCALE + 0.5) - (5 * INST))
#define TIME_800_1 ((int)(0.80 * SCALE + 0.5) - (5 * INST))
#define PERIOD_800 ((int)(1.25 * SCALE + 0.5) - (5 * INST))
#define TIME_400_0 ((int)(0.50 * SCALE + 0.5) - (5 * INST))
#define TIME_400_1 ((int)(1.20 * SCALE + 0.5) - (5 * INST))
#define PERIOD_400 ((int)(2.50 * SCALE + 0.5) - (5 * INST))
int pinMask, time0, time1, period, t;
Pio *port;
volatile WoReg *portSet, *portClear, *timeValue, *timeReset;
uint8_t *p, *end, pix, mask;
pmc_set_writeprotect(false);
pmc_enable_periph_clk((uint32_t)TC3_IRQn);
TC_Configure(TC1, 0,
TC_CMR_WAVE | TC_CMR_WAVSEL_UP | TC_CMR_TCCLKS_TIMER_CLOCK1);
TC_Start(TC1, 0);
pinMask = g_APinDescription[pin].ulPin; // Don't 'optimize' these into
port = g_APinDescription[pin].pPort; // declarations above. Want to
portSet = &(port->PIO_SODR); // burn a few cycles after
portClear = &(port->PIO_CODR); // starting timer to minimize
timeValue = &(TC1->TC_CHANNEL[0].TC_CV); // the initial 'while'.
timeReset = &(TC1->TC_CHANNEL[0].TC_CCR);
p = pixels;
end = p + numBytes;
pix = *p++;
mask = 0x80;
#ifdef NEO_KHZ400
if((type & NEO_SPDMASK) == NEO_KHZ800) { // 800 KHz bitstream
#endif
time0 = TIME_800_0;
time1 = TIME_800_1;
period = PERIOD_800;
#ifdef NEO_KHZ400
} else { // 400 KHz bitstream
time0 = TIME_400_0;
time1 = TIME_400_1;
period = PERIOD_400;
}
#endif
for(t = time0;; t = time0) {
if(pix & mask) t = time1;
while(*timeValue < period);
*portSet = pinMask;
*timeReset = TC_CCR_CLKEN | TC_CCR_SWTRG;
while(*timeValue < t);
*portClear = pinMask;
if(!(mask >>= 1)) { // This 'inside-out' loop logic utilizes
if(p >= end) break; // idle time to minimize inter-byte delays.
pix = *p++;
mask = 0x80;
}
}
while(*timeValue < period); // Wait for last bit
TC_Stop(TC1, 0);
#endif // end Arduino Due
#endif // end Architecture select
interrupts();
endTime = micros(); // Save EOD time for latch on next call
}
// Set the output pin number
void Adafruit_NeoPixel::setPin(uint8_t p) {
pinMode(pin, INPUT);
pin = p;
pinMode(p, OUTPUT);
digitalWrite(p, LOW);
#ifdef __AVR__
port = portOutputRegister(digitalPinToPort(p));
pinMask = digitalPinToBitMask(p);
#endif
}
// Set pixel color from separate R,G,B components:
void Adafruit_NeoPixel::setPixelColor(
uint16_t n, uint8_t r, uint8_t g, uint8_t b) {
if(n < numLEDs) {
if(brightness) { // See notes in setBrightness()
r = (r * brightness) >> 8;
g = (g * brightness) >> 8;
b = (b * brightness) >> 8;
}
uint8_t *p = &pixels[n * 3];
p[rOffset] = r;
p[gOffset] = g;
p[bOffset] = b;
}
}
// Set pixel color from 'packed' 32-bit RGB color:
void Adafruit_NeoPixel::setPixelColor(uint16_t n, uint32_t c) {
if(n < numLEDs) {
uint8_t
r = (uint8_t)(c >> 16),
g = (uint8_t)(c >> 8),
b = (uint8_t)c;
if(brightness) { // See notes in setBrightness()
r = (r * brightness) >> 8;
g = (g * brightness) >> 8;
b = (b * brightness) >> 8;
}
uint8_t *p = &pixels[n * 3];
p[rOffset] = r;
p[gOffset] = g;
p[bOffset] = b;
}
}
// Convert separate R,G,B into packed 32-bit RGB color.
// Packed format is always RGB, regardless of LED strand color order.
uint32_t Adafruit_NeoPixel::Color(uint8_t r, uint8_t g, uint8_t b) {
return ((uint32_t)r << 16) | ((uint32_t)g << 8) | b;
}
// Query color from previously-set pixel (returns packed 32-bit RGB value)
uint32_t Adafruit_NeoPixel::getPixelColor(uint16_t n) const {
if(n >= numLEDs) {
// Out of bounds, return no color.
return 0;
}
uint8_t *p = &pixels[n * 3];
uint32_t c = ((uint32_t)p[rOffset] << 16) |
((uint32_t)p[gOffset] << 8) |
(uint32_t)p[bOffset];
// Adjust this back up to the true color, as setting a pixel color will
// scale it back down again.
if(brightness) { // See notes in setBrightness()
//Cast the color to a byte array
uint8_t * c_ptr =reinterpret_cast<uint8_t*>(&c);
c_ptr[0] = (c_ptr[0] << 8)/brightness;
c_ptr[1] = (c_ptr[1] << 8)/brightness;
c_ptr[2] = (c_ptr[2] << 8)/brightness;
}
return c; // Pixel # is out of bounds
}
// Returns pointer to pixels[] array. Pixel data is stored in device-
// native format and is not translated here. Application will need to be
// aware whether pixels are RGB vs. GRB and handle colors appropriately.
uint8_t *Adafruit_NeoPixel::getPixels(void) const {
return pixels;
}
uint16_t Adafruit_NeoPixel::numPixels(void) const {
return numLEDs;
}
// Adjust output brightness; 0=darkest (off), 255=brightest. This does
// NOT immediately affect what's currently displayed on the LEDs. The
// next call to show() will refresh the LEDs at this level. However,
// this process is potentially "lossy," especially when increasing
// brightness. The tight timing in the WS2811/WS2812 code means there
// aren't enough free cycles to perform this scaling on the fly as data
// is issued. So we make a pass through the existing color data in RAM
// and scale it (subsequent graphics commands also work at this
// brightness level). If there's a significant step up in brightness,
// the limited number of steps (quantization) in the old data will be
// quite visible in the re-scaled version. For a non-destructive
// change, you'll need to re-render the full strip data. C'est la vie.
void Adafruit_NeoPixel::setBrightness(uint8_t b) {
// Stored brightness value is different than what's passed.
// This simplifies the actual scaling math later, allowing a fast
// 8x8-bit multiply and taking the MSB. 'brightness' is a uint8_t,