From 147f920eb6a19718a20a15d598f9d579ba01e2d2 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Wed, 14 May 2025 01:48:24 +0200
Subject: [PATCH] avr/sk6812: improved protocol implementation.

still doesn't work with new 5m LED strips from BTF-Lighting (1m strips
do work, as do older 5m stripes).
---
 avr/modules/sk6812/main.asm | 119 +++++++++++++++---------------------
 1 file changed, 50 insertions(+), 69 deletions(-)

diff --git a/avr/modules/sk6812/main.asm b/avr/modules/sk6812/main.asm
index 1671ed1..ba1ad37 100644
--- a/avr/modules/sk6812/main.asm
+++ b/avr/modules/sk6812/main.asm
@@ -154,92 +154,73 @@ sk6812SendPattern_loop2:
 
 sk6812SendQuadruple:
   mov r16, r19     ; G
-  rcall sk6812SendByte2  ; (r16, r17, r24, r25)
+  rcall sk6812SendByte4  ; (r16, r17, r24, r25)
   mov r16, r18     ; R
-  rcall sk6812SendByte2  ; (r16, r17, r24, r25)
+  rcall sk6812SendByte4  ; (r16, r17, r24, r25)
   mov r16, r20     ; B
-  rcall sk6812SendByte2  ; (r16, r17, r24, r25)
+  rcall sk6812SendByte4  ; (r16, r17, r24, r25)
   mov r16, r21     ; W
-  rcall sk6812SendByte2  ; (r16, r17, r24, r25)
+  rcall sk6812SendByte4  ; (r16, r17, r24, r25)
   ret
 ; @end
 
 
 
-#if 0
+
 ; ---------------------------------------------------------------------------
-; @routine sk6812SendByte
+; @macro M_SK6812_HANDLEBIT
+
+.macro M_SK6812_HANDLEBIT
+  lsl r16                          ; +1
+  brcs l_sendOne                   ; +1 if false, +2 if branch taken
+  ; send ZERO
+  nop                              ; +1
+  out SK6812_PORT, r25             ; +1   HIGH
+  nop
+  nop
+  nop
+  out SK6812_PORT, r24             ; +1
+  nop                              ; +1
+  rjmp l_end                       ; +2
+l_sendOne:
+  out SK6812_PORT, r25             ; +1   HIGH
+  nop                              ; +1
+  nop                              ; +1
+  nop                              ; +1
+  nop                              ; +1
+  nop                              ; +1
+  out SK6812_PORT, r24             ; +1
+  nop                              ; +1
+l_end:
+.endmacro
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine sk6812SendByte4
 ;
 ; reset: 80microsecs
-; 0: 300ns high, 900ns low  (+/- 150ns)
-; 1: 600ns high, 600ns low  (+/- 150ns)
+; 0: 500ns high, 750ns low  (+/- 150ns)
+; 1: 750ns high, 500ns low  (+/- 150ns)
+; 8 ticks per cycle
 ;
 ; @param r16 value
 ; @clobbers r16, r17, r24, r25
 
-sk6812SendByte:
-  ldi r17, 8                         ; +1
-  ldi r24, (1<<SK6812_PINNUM)
-  clr r25
-sk6812SendByte_loop:
-    lsl r16                          ; +1
-    brcs sk6812SendByte_sendOne      ; +1 if false, +2 if branch taken
-    nop                              ; +1
-    ; send ZERO
-    out SK6812_PORT, r24             ; +1 set HIGH
-    nop                              ; +1
-    out SK6812_PORT, r25             ; +1 set LOW
-    dec r17                          ; +1
-  brne sk6812SendByte_loop           ; +1 if false, +2 if branch taken
-  ret                                ; 4
-  
-sk6812SendByte_sendOne:
-    out SK6812_PORT, r24             ; +1 set HIGH
-    nop                              ; +1
-    nop                              ; +1
-    nop                              ; +1
-    nop                              ; +1
-    out SK6812_PORT, r25             ; +1 set LOW
-    dec r17                          ; +1
-  brne sk6812SendByte_loop           ; +2
-  ret
-; @end
-#endif
+sk6812SendByte4:
+  ldi r24, 0
+  ldi r25, (1<<SK6812_PINNUM)
 
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
 
-
-; ---------------------------------------------------------------------------
-; @routine sk6812SendByte2
-;
-; reset: 80microsecs
-; 0: 300ns high, 900ns low  (+/- 150ns)
-; 1: 600ns high, 600ns low  (+/- 150ns)
-;
-; @param r16 value
-; @clobbers r16, r17
-
-sk6812SendByte2:
-  ldi r17, 8                         ; +1
-sk6812SendByte2_loop:
-    lsl r16                          ; +1
-    brcs sk6812SendByte2_sendOne     ; +1 if false, +2 if branch taken
-    nop                              ; +1
-    ; send ZERO
-    sbi SK6812_PORT, SK6812_PINNUM   ; +2 set HIGH
-    nop                              ; +1  (125ns)
-    cbi SK6812_PORT, SK6812_PINNUM   ; +2 set LOW    (250ns)
-    dec r17                          ; +1  (125ns)
-  brne sk6812SendByte2_loop          ; +1 if false, +2 if branch taken
-  ret                                ; +4
-  
-sk6812SendByte2_sendOne:
-    sbi SK6812_PORT, SK6812_PINNUM   ; +2 set HIGH
-    nop                              ; +1 (125ns)
-    nop                              ; +1 (125ns)
-    nop                              ; +1 (125ns)
-    cbi SK6812_PORT, SK6812_PINNUM   ; +2 set LOW
-    dec r17                          ; +1
-  brne sk6812SendByte2_loop          ; +1 if false, +2 if branch taken
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
+  M_SK6812_HANDLEBIT
   ret                                ; +4
 ; @end