David Knight / PololuLedStrip

This library lets you control the addressable RGB LED strips from Pololu Robotics. Forked to add selectable colour order (Support RGB or GRB Leds)

Fork of PololuLedStrip by David Grayson

Files at this revision

API Documentation at this revision

Revision 5:690fdfb595de, committed 2013-03-01

Comitter:
DavidEGrayson
Date:
Fri Mar 01 00:05:26 2013 +0000
Parent:
4:d3b60bd43811
Child:
6:9d0530b7dae2
Commit message:
It looks like the code is transmitting the right number of bits now.

Changed in this revision

led_strip_write_color.s Show annotated file Show diff for this revision Revisions of this file 
--- a/led_strip_write_color.s	Thu Feb 28 00:42:44 2013 +0000
+++ b/led_strip_write_color.s	Fri Mar 01 00:05:26 2013 +0000
@@ -2,7 +2,20 @@
     EXPORT led_strip_write_color
 
 led_strip_write_color
-    push    {r4, r12, r7}
+    ; Register usage:
+    ; These are the first 4 arguments to the method:
+    ;   R0:  pointer to the color to send
+    ;   R1:  pointer to the register for setting the pin
+    ;   R2:  pointer to the register for clearing the pin
+    ;   R3:  pin mask
+    ; Additionally, we use these registers:
+    ;   R4:  temporary register
+    ;   R7:  the number of bits we still need to send
+    ;   R12: shift register that holds the 24-bit color
+    ;   R13: Link Register, holds return addresses.
+    
+    
+    push    {r4, r12, r7, lr}
    
     ldr r12, [r0]      ; Read the next color.
     rbit r12, r12      ; Reverse the order of the bits.
@@ -13,164 +26,34 @@
     str r3, [r1]       ; Drive the line high.
     rrxs r12, r12      ; Rotate right through carry.
     
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-        
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-        
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-        
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-        
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
+    ldr r4, =delay_region_end
+    sub r4, r4, #59*2
+    blx r4
     
     it cc                ; If the bit to send it 0...
     strcc r3, [r2]       ; Drive the line low.
 
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-    nop
-
+    ldr r4, =delay_region_end
+    sub r4, r4, #59*2
+    blx r4
 
     it cs                ; If the bit to send is 1...
     strcs r3, [r2]       ; Drive the line low.
     
     ldr r4, =delay_region
-    add r4, r4, 34*2
+    add r4, r4, #68
     blx r4
     
-    sub r7, r7, #1               ; Decrement the loop counter.
-    cbz r7, led_strip_asm_end    ; If we have sent 24 bits, go to the end.
-    b send_led_strip_bit         ; Otherwise, go back and send another bit.
+    subs r7, r7, #1            ; Decrement the loop counter.
+    bne send_led_strip_bit    ; Send another bit if we have not reached zero.
     
 led_strip_asm_end
-    pop {r4, r12, r7}
+    pop {r4, r12, r7, lr}
     bx lr
     
 
 delay_region
-    ; The following is 128 no-ops
+    ; The following is 128 nops.
     nop
     nop
     nop
@@ -306,6 +189,7 @@
     nop
     nop
     nop
+delay_region_end
     bx lr    ; return
     
     END
\ No newline at end of file