Diff: frameout.s

Revision:

0:f16a1d69a386

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/frameout.s	Wed Feb 29 17:01:43 2012 +0000
@@ -0,0 +1,77 @@
+   AREA framefunc, CODE, READONLY
+; Export my_asm function location so that C compiler can find it and link
+    EXPORT frameout
+frameout
+
+; r0 - dsVal array base address
+; r1 - data array base address
+; r2 - base address for port 0
+; r3 - loop counter
+; r4 - sclk bitmask
+; r5 - RGB channels bitmask
+; r6 - data reg 1
+; r7 - data reg 2
+; r8 - temporary value holding intensity info (used as an offset into dsVal array)
+
+
+; Save state
+    PUSH {R4, R5, R6, R7, R8}
+
+; Load GPIO Port 0 base address in register R6 
+    LDR     R2, =0x2009C000 ; GPIO port 0 base address
+    
+; R3 - loop counter
+    MOV     R3, #256
+    
+; sclk mask
+    MOV     R4, #0x00010000 ; sclk bitmask
+    
+; RGB channels mask
+    MOV     R5, #0x03800000 ; bitmask for RGB bits
+    
+LOOP
+    
+;NOTE clocking swapped due to inverter used for logic levels|
+    ;STR     R4, [R2, #0x18] ; setting clock high
+    STR     R4, [R2, #0x1C] ; cleark clk to clock in data (negative edge)
+
+    
+    STR     R5, [R2, #0x1C] ; clear RGB via FIOCLEAR
+    
+    ; R channel
+    LDRB     R8, [R1], #1 ; read data word (0-255 intensity) and post-increment array pointer to point to next word in data
+    LDRB     R6, [R0, R8] ; loading on/off state from dsVal, pointed to by offset equal to intensity of data
+        
+  
+    ; G channel  
+    LDRB     R8, [R1], #1 ; read data word (0-255 intensity) into R8 and post-increment to point to next word in data
+    LDRB     R7, [R0, R8] ; loading on/off state from dsVal, pointed to by offset equal to intensity of data
+    
+    AND     R7, R7, #0x2 ; pick blue channel bit
+    
+    ORR     R6, R7, R6, lsr #7 ; store RG bits in R6 with clever stuff in R chan
+    
+    ; B channel
+    LDRB     R8, [R1], #1 ; read data word (0-255 intensity) into R8 and post-increment to point to next word in data
+    LDRB     R7, [R0, R8] ; loading on/off state from dsVal, pointed to by offset equal to intensity of data    
+    
+    AND     R7, R7, #0x4 ; pick green channel bit
+    
+    ; writing to output
+    ORR     R6, R6, R7 ; RGB bits in R6
+    
+    MOV     R6, R6, lsl #23 
+
+    STR     R6, [R2,#0x18] ; FIOSET on/off for LED
+    
+    SUBS    R3, R3, #0x1 ; decrement loop counter
+
+    STR     R4, [R2, #0x18] ; setting clock high
+    
+    
+    BNE     LOOP
+    
+    POP {R4, R5, R6, R7, R8}
+
+    BX      LR
+    END