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Arduboy2
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Merge pull request #9 from yyyc514/pixel_performance 

Pixel performance improvements
This commit is contained in:
Scott Allen 2017-04-18 12:31:33 -04:00 committed by GitHub
parent 142d85415c d999733320
commit 36bbfa89ab
2 changed files with 45 additions and 10 deletions
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51
src/Arduboy2.cpp
View File

@ -267,6 +267,14 @@ void Arduboy2Base::clear()
fillScreen(BLACK);
}
// Used by drawPixel to help with left bitshifting since AVR has no
// multiple bit shift instruction. We can bit shift from a lookup table
// in flash faster than we can calculate the bit shifts on the CPU.
PROGMEM const unsigned char bitshift_left[] = {
1, 2, 4, 8, 16, 32, 64, 128
};
void Arduboy2Base::drawPixel(int16_t x, int16_t y, uint8_t color)
{
#ifdef PIXEL_SAFE_MODE
@ -276,14 +284,41 @@ void Arduboy2Base::drawPixel(int16_t x, int16_t y, uint8_t color)
}
#endif
uint8_t row = (uint8_t)y / 8;
if (color)
{
sBuffer[(row*WIDTH) + (uint8_t)x] |= _BV((uint8_t)y % 8);
}
else
{
sBuffer[(row*WIDTH) + (uint8_t)x] &= ~ _BV((uint8_t)y % 8);
uint16_t row_offset;
uint8_t bit;
// uint8_t row = (uint8_t)y / 8;
// row_offset = (row*WIDTH) + (uint8_t)x;
// bit = _BV((uint8_t)y % 8);
// the above math can also be rewritten more simply as;
// (y * WIDTH/8) & ~0b01111111 + (uint8_t)x;
// which is what the below assembler does
asm volatile(
"mul %[width_offset],%[y]\n"
"movw %[row_offset], r0\n"
"andi %A[row_offset], 0x80\n" // row_offset &= (~0b01111111);
"clr __zero_reg__\n"
"add %A[row_offset], %[x]\n"
// mask for only 0-7
"andi %[y], 0x07\n"
// Z += y
"add r30, %[y]\n"
"adc r31, __zero_reg__\n"
// load correct bitshift from program RAM
"lpm %[bit], Z\n"
: [row_offset] "=x&" (row_offset), // upper register (ANDI)
[bit] "=r" (bit)
: [width_offset] "r" ((uint8_t)(WIDTH/8)),
[x] "r" ((uint8_t)x),
[y] "a" ((uint8_t)y), // upper register (ANDI)
"z" (bitshift_left)
: "r1", "r0");
if (color) {
sBuffer[row_offset] |= bit;
} else {
sBuffer[row_offset] &= ~ bit;
}
}

4
src/Arduboy2.h
View File

@ -386,7 +386,7 @@ class Arduboy2Base : public Arduboy2Core
* specified color. The values WHITE or BLACK can be used for the color.
* If the `color` parameter isn't included, the pixel will be set to WHITE.
*/
void drawPixel(int16_t x, int16_t y, uint8_t color = WHITE);
void drawPixel(int16_t x, int16_t y, uint8_t color = WHITE);
/** \brief
* Returns the state of the given pixel in the screen buffer.
@ -1210,7 +1210,7 @@ class Arduboy2 : public Print, public Arduboy2Base
*
* \details
* This function is called by `bootLogoShell()` and `bootlogoText()`.
*
*
* If a unit name has been saved in system EEPROM, it will be displayed at
* the bottom of the screen. This function pauses for a short time to allow
* the name to be seen.