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Refactor fillScreen()

This commit is contained in:
Scott Allen 2017-06-16 18:37:19 -04:00
parent bd5b470294
commit b121d19b77
1 changed files with 31 additions and 21 deletions
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52
src/Arduboy2.cpp
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@ -599,39 +599,49 @@ void Arduboy2Base::fillRect
void Arduboy2Base::fillScreen(uint8_t color) void Arduboy2Base::fillScreen(uint8_t color)
{ {
// C version : // C version:
// //
// if (color) color = 0xFF; //change any nonzero argument to b11111111 and insert into screen array. // if (color != BLACK)
// for(int16_t i=0; i<1024; i++) { sBuffer[i] = color; } //sBuffer = (128*64) = 8192/8 = 1024 bytes. // {
// color = 0xFF; // all pixels on
// }
// for (int16_t i = 0; i < WIDTH * HEIGTH / 8; i++)
// {
// sBuffer[i] = color;
// }
// This asm version is hard coded for 1024 bytes. It doesn't use the defined
// WIDTH and HEIGHT values. It will have to be modified for a different
// screen buffer size.
// It also assumes color value for BLACK is 0.
// local variable for screen buffer pointer,
// which can be declared a read-write operand
uint8_t* bPtr = sBuffer;
asm volatile asm volatile
( (
// load color value into r27
"mov r27, %1 \n\t"
// if value is zero, skip assigning to 0xff // if value is zero, skip assigning to 0xff
"cpse r27, __zero_reg__ \n\t" "cpse %[color], __zero_reg__\n"
"ldi r27, 0xff \n\t" "ldi %[color], 0xFF\n"
// load sBuffer pointer into Z
"movw r30, %0\n\t"
// counter = 0 // counter = 0
"clr __tmp_reg__ \n\t" "clr __tmp_reg__\n"
"loopto: \n\t" "loopto:\n"
// (4x) push zero into screen buffer, // (4x) push zero into screen buffer,
// then increment buffer position // then increment buffer position
"st Z+, r27 \n\t" "st Z+, %[color]\n"
"st Z+, r27 \n\t" "st Z+, %[color]\n"
"st Z+, r27 \n\t" "st Z+, %[color]\n"
"st Z+, r27 \n\t" "st Z+, %[color]\n"
// increase counter // increase counter
"inc __tmp_reg__ \n\t" "inc __tmp_reg__\n"
// repeat for 256 loops // repeat for 256 loops
// (until counter rolls over back to 0) // (until counter rolls over back to 0)
"brne loopto \n\t" "brne loopto\n"
// input: sBuffer, color : [color] "+d" (color),
// modified: Z (r30, r31), r27 "+z" (bPtr)
:
: :
: "r" (sBuffer), "r" (color)
: "r30", "r31", "r27"
); );
} }