Raspberry Pi LCD without i2c

main.go

package main

import (
	"fmt"
	"os"
	"time"

	"github.com/stianeikeland/go-rpio"
)

const InstructionClearDisplay = 0b00000001
const InstructionReturnHome = 0b00000010
const InstructionFunctionSet = 0b00100000
const InstructionFunctionSetDataLength8Bit = 0b00010000
const InstructionFunctionSetOneLine = 0b00001000
const InstructionFunctionSetTwoLine = 0b00000000
const InstructionFunctionSet5By11 = 0b00000000
const InstructionFunctionSet5By8 = 0b00000001
const InstructionDisplayControl = 0b00001000
const InstructionDisplayControlOn = 0b00000100
const InstructionDisplayControlOff = 0b00000000
const InstructionDisplayControlCursorOn = 0b00000010
const InstructionDisplayControlCursorOff = 0b00000000
const InstructionDisplayControlCursorBlinkOn = 0b00000001
const InstructionDisplayControlCursorBlinkOff = 0b00000000

const InstructionCursorOrDisplayShift = 0b00010000
const InstructionCursorOrDisplayShiftCursor = 0b00001000

var characters = map[rune]uint8{
	' ': 0b00000000,
	'A': 0b01000001,
	'B': 0b01000010,
	'C': 0b01000011,
	'D': 0b01000100,
	'E': 0b01000101,
	'F': 0b01000110,
	'G': 0b01000111,
	'H': 0b01001000,
	'I': 0b01001001,
	'J': 0b01001010,
	'K': 0b01001011,
	'L': 0b01001100,
	'M': 0b01001101,
	'N': 0b01001110,
	'O': 0b01001111,
	'P': 0b01010000,
	'Q': 0b01010001,
	'R': 0b01010010,
	'S': 0b01010011,
	'T': 0b01010100,
	'U': 0b01010101,
	'V': 0b01010110,
	'W': 0b01010111,
	'X': 0b01011000,
	'Y': 0b01011001,
	'Z': 0b01011010,
}

func main() {
	err := rpio.Open()
	if err != nil {
		fmt.Printf("error opening up GPIO: %v\n", err)
		os.Exit(1)
	}
	registerSelect := rpio.Pin(17)
	registerSelect.Output()
	enable := rpio.Pin(27)
	enable.Output()
	enable.Low()
	bit0 := rpio.Pin(22)
	bit0.Output()
	bit1 := rpio.Pin(10)
	bit1.Output()
	bit2 := rpio.Pin(9)
	bit2.Output() 
	bit3 := rpio.Pin(11)
	bit3.Output()
	bit4 := rpio.Pin(23)
	bit4.Output()
	bit5 := rpio.Pin(24)
	bit5.Output()
	bit6 := rpio.Pin(25)
	bit6.Output()
	bit7 := rpio.Pin(8)
	bit7.Output()

	write := func(instruction bool, data uint8) {
		highLow(!instruction, registerSelect)
		writeBit(data, 1, bit0)
		writeBit(data, 2, bit1)
		writeBit(data, 4, bit2)
		writeBit(data, 8, bit3)
		writeBit(data, 16, bit4)
		writeBit(data, 32, bit5)
		writeBit(data, 64, bit6)
		writeBit(data, 128, bit7)
		enable.High()
		time.Sleep(100 * time.Microsecond)
		enable.Low()
	}

	// Initialise as per Hitachi data sheet.
	time.Sleep(100 * time.Millisecond)
	write(true, InstructionFunctionSet | InstructionFunctionSetDataLength8Bit)
	time.Sleep(5 * time.Millisecond)
	write(true, InstructionFunctionSet | InstructionFunctionSetDataLength8Bit)
	time.Sleep(1 * time.Millisecond)
	write(true, InstructionFunctionSet | InstructionFunctionSetDataLength8Bit)
	time.Sleep(1 * time.Millisecond)

	write(true, InstructionFunctionSet | InstructionFunctionSetDataLength8Bit | InstructionFunctionSetTwoLine | InstructionFunctionSet5By8)
	time.Sleep(1 * time.Millisecond)
	write(true, InstructionDisplayControl|InstructionDisplayControlOn)
	time.Sleep(1 * time.Millisecond)
	write(true, InstructionClearDisplay)
	time.Sleep(1 * time.Millisecond)

	writeText := func(text string) {
		for _, c := range text {
			if data, ok := characters[c]; ok {
				write(false, data)
			}
		}
	}
	writeText("ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ")
}

func writeBit(data, bit uint8, pin rpio.Pin) {
	highLow((data&bit) == bit, pin)
}

func highLow(v bool, pin rpio.Pin) {
	if v {
		pin.High()
	} else {
		pin.Low()
	}
}