Add Hd44780i2c driver (#173)

* hd44780i2c: add support for hd44780i2c LCD display.

examples/hd44780i2c/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"machine"
+	"strconv"
+	"time"
+
+	"tinygo.org/x/drivers/hd44780i2c"
+)
+
+func main() {
+
+	// Note: most HD44780 LCD modules requires 5V power, however some variations
+	// use 3.3V (and may be damaged by 5V).
+
+	machine.I2C0.Configure(machine.I2CConfig{
+		Frequency: machine.TWI_FREQ_400KHZ,
+	})
+
+	lcd := hd44780i2c.New(machine.I2C0, 0x27) // some modules have address 0x3F
+
+	lcd.Configure(hd44780i2c.Config{
+		Width:       16, // required
+		Height:      2,  // required
+		CursorOn:    true,
+		CursorBlink: true,
+	})
+
+	lcd.Print([]byte(" TinyGo\n  LCD Test "))
+
+	// CGRAM address 0x0-0x7 can be used to store 8 custom characters
+	lcd.CreateCharacter(0x0, []byte{0x00, 0x11, 0x0E, 0x1F, 0x15, 0x1F, 0x1F, 0x1F})
+	lcd.Print([]byte{0x0})
+
+	// You can use https://maxpromer.github.io/LCD-Character-Creator/
+	// to crete your own characters.
+
+	time.Sleep(time.Millisecond * 7000)
+
+	for i := 0; i < 5; i++ {
+		lcd.BacklightOn(false)
+		time.Sleep(time.Millisecond * 250)
+		lcd.BacklightOn(true)
+		time.Sleep(time.Millisecond * 250)
+	}
+
+	lcd.CursorOn(false)
+	lcd.CursorBlink(false)
+
+	i := 0
+	for {
+
+		lcd.ClearDisplay()
+		lcd.SetCursor(2, 1)
+		lcd.Print([]byte(strconv.FormatInt(int64(i), 10)))
+		i++
+		time.Sleep(time.Millisecond * 100)
+
+	}
+}