uc8151: improvements to speed and also add flicker-free mode based on @antirez code example

Signed-off-by: deadprogram <ron@hybridgroup.com>

examples/uc8151/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"image/color"
 	"machine"
+	"time"
 
 	"tinygo.org/x/drivers"
 	"tinygo.org/x/drivers/uc8151"
@@ -15,30 +16,56 @@ func main() {
 	led = machine.LED
 	led.Configure(machine.PinConfig{Mode: machine.PinOutput})
 	machine.SPI0.Configure(machine.SPIConfig{
-		Frequency: 12000000,
+		Frequency: 12 * machine.MHz,
 		SCK:       machine.EPD_SCK_PIN,
 		SDO:       machine.EPD_SDO_PIN,
 	})
 
 	display = uc8151.New(machine.SPI0, machine.EPD_CS_PIN, machine.EPD_DC_PIN, machine.EPD_RESET_PIN, machine.EPD_BUSY_PIN)
 	display.Configure(uc8151.Config{
-		Rotation: drivers.Rotation270,
-		Speed:    uc8151.MEDIUM,
-		Blocking: true,
+		Rotation:    drivers.Rotation270,
+		Speed:       uc8151.TURBO,
+		FlickerFree: true,
+		Blocking:    false,
 	})
 	black := color.RGBA{1, 1, 1, 255}
 
-	display.ClearBuffer()
-	display.Display()
-	for i := int16(0); i < 37; i++ {
-		for j := int16(0); j < 16; j++ {
-			if (i+j)%2 == 0 {
-				showRect(i*8, j*8, 8, 8, black)
+	display.ClearDisplay()
+
+	mod := int16(1)
+	for {
+		// checkerboard
+		for i := int16(0); i < 11; i++ {
+			if mod == 1 {
+				mod = 0
+			} else {
+				mod = 1
+			}
+
+			display.ClearBuffer()
+			for i := int16(0); i < 37; i++ {
+				for j := int16(0); j < 16; j++ {
+					if (i+j)%2 == mod {
+						showRect(i*8, j*8, 8, 8, black)
+					}
+				}
+			}
+			display.Display()
+			time.Sleep(500 * time.Millisecond)
+		}
+
+		// moving line
+		for i := int16(16); i < 21; i++ {
+			display.ClearBuffer()
+			for j := int16(0); j < 16; j++ {
+				if (i+j)%2 == 0 {
+					showRect(i*8, j*8, 8, 8, black)
+				}
+				display.Display()
+				time.Sleep(250 * time.Millisecond)
 			}
 		}
 	}
-
-	display.Display()
 }
 
 func showRect(x int16, y int16, w int16, h int16, c color.RGBA) {