just suggested update to adafruit libray for st77xx display. 

this is for 4 writes at a time feature. 16x writes feature will be submitted later on.

in order to do so i added in safety checks to ensure spi data had competed for different spi data rates. i ensured that most if not all the time the loop back function of while(!(SPSR & (1<<SPIF) )); or equivalent would jus pass thru when spi is at full speed, if spi speed is slower it will wait and loop back for spi data to complete. it reduces performance by 5%, but makes it easier for new users to manage, and it reduces troubleshooting issues. it still is about 4x-8x faster than normal, as spi data is burst twice as fast as normal, and pixel location and window size overhead is reduced by 4x.

here my submission to them below:

would you add a method that allows for up to 4 writes at a time together? #52

 Open jamesdanielv opened this issue 6 minutes ago · 0 comments

it is unrolled a bit so some unconventional steps are used to make it more manageable, such as '#define' used to create complex commands. this code takes a large rectangle area, and subdivides it into 4 areas that can have different color values. while(!(SPSR & (1<<SPIF) )) is used as a safety check but should normally run thru without loop back or jmp performance tax, unless spi is at a lower speed. within this function spi is burst at about 80-100% increase speed from normal at max spi data rate, and overhead of pixel location and window size is reduced by 4x!

void Adafruit_ST77xx::fillRectFast4colors(int16_t x, int16_t y, int16_t w, int16_t h, uint16_t color0,uint16_t color1,uint16_t color2,uint16_t color3) { //this is needed for text but not fills with solid color! // rudimentary clipping (drawChar w/big text requires this) // if((x >= _width) || (y >= _height)) return; // if((x + w - 1) >= _width) w = _width - x; // if((y + h - 1) >= _height) h = _height - y;

setAddrWindow(x, y, x+w-1, y+h-1);

SPI_BEGIN_TRANSACTION(); //created complex commands in #define so code can be a lot cleaner //this is a complex command that complexspi= hi[0] value #define complexspi SPCRbackup = SPCR; SPCR = mySPCR; SPDR //this is small delay #define shortSpiDelay asm("nop\n\t");// asm("nop\n\t");// asm("nop\n\t"); //last comment out ';' not needed here, but can be added in commands later #define longSpiDelay asm("nop\n\t"); asm("nop\n\t");asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t"); asm("nop\n\t");// asm("nop\n\t");// asm("nop\n\t");// asm("nop\n\t");// asm("nop\n\t")

digitalWriteFast(TFT_DC,HIGH);// old DC_HIGH(); digitalWriteFast(TFT_CS,LOW);// old CS_LOW();

// y=h; uint16_t countx;//we use these to understand what to draw! uint16_t county;

SPCR = SPCRbackup; //we place at top for next loop iteration county=h/2;

while (county !=0 ){countx=w/2;while (countx !=0) {while(!(SPSR & (1<<SPIF) ));;complexspi = highByte(color0);longSpiDelay;while(!(SPSR & (1<<SPIF) )); complexspi =lowByte(color0) ;shortSpiDelay;countx--;} while(!(SPSR & (1<<SPIF) ));

countx=w/2; while (countx !=0) {while(!(SPSR & (1<<SPIF) ));;complexspi =highByte(color1);longSpiDelay;while(!(SPSR & (1<<SPIF) )); complexspi=lowByte(color1);shortSpiDelay;countx--;} while(!(SPSR & (1<<SPIF) ));

county--; }//end of first half of rectange [0][1] drawn! county=h/2; while (county !=0){countx=w/2;while (countx !=0) {while(!(SPSR & (1<<SPIF) ));;complexspi = highByte(color2);longSpiDelay;while(!(SPSR & (1<<SPIF) )); complexspi =lowByte(color2);shortSpiDelay;countx--;} while(!(SPSR & (1<<SPIF) ));

countx=w/2;while (countx !=0) {while(!(SPSR & (1<<SPIF) ));;complexspi = highByte(color3);longSpiDelay;while(!(SPSR & (1<<SPIF) )); complexspi =lowByte(color3);shortSpiDelay; countx--;} county--; }//end of first half of rectange [2][3] drawn! while(!(SPSR & (1<<SPIF) )); digitalWriteFast(TFT_DC,HIGH);// old DC_HIGH(); digitalWriteFast(TFT_CS,HIGH);//old CS_HIGH(); SPI_END_TRANSACTION(); }