Oskar Weigl
/
LED_for_hackspace
LED screen driver build for hackspace.
Diff: frameout.s
- Revision:
- 0:f16a1d69a386
diff -r 000000000000 -r f16a1d69a386 frameout.s --- /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