Hitachi HD44780U Dot Matrix Liquid Crystal Display (#223)

Signed-off-by: Eugene Dzhurinsky <jdevelop@gmail.com>

AUTHORS

@@ -4,6 +4,7 @@
 # some cases, their employer may be the copyright holder.  To see the full list
 # of contributors, see the revision history in source control.
 Cássio Botaro <cassiobotaro@gmail.com>
+Fractal Industries, Inc
 Google Inc.
 Matt Aimonetti <mattaimonetti@gmail.com>
 Max Ekman <max@looplab.se>

experimental/devices/hd44780/hd44780.go

@@ -0,0 +1,242 @@
+// Copyright 2018 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+// Package hd44780 controls the Hitachi LCD display chipset HD-44780
+//
+// Datasheet
+//
+// https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
+package hd44780
+
+import (
+	"fmt"
+	"time"
+
+	"periph.io/x/periph/conn"
+	"periph.io/x/periph/conn/gpio"
+)
+
+// lineTwo offset for the second line in the LCD buffer.
+const lineTwo = 0x40
+
+// Dev is the 4-bit addressing device for HD-44780
+type Dev struct {
+	// data pins
+	dataPins []gpio.PinOut
+
+	// register select pin
+	rsPin gpio.PinOut
+
+	// enable pin
+	enablePin gpio.PinOut
+}
+
+// New creates and initializes the LCD device
+//	data - references to data pins
+//	rs - rs pin
+//	e - strobe pin
+func New(data []gpio.PinOut, rs, e gpio.PinOut) (*Dev, error) {
+	if len(data) != 4 {
+		return nil, fmt.Errorf("expected 4 data pins, passed %s", len(data))
+	}
+	dev := &Dev{
+		dataPins:  data,
+		enablePin: e,
+		rsPin:     rs,
+	}
+	if err := dev.Reset(); err != nil {
+		return nil, err
+	}
+	return dev, nil
+}
+
+// Reset resets the HC-44780 chipset, clears the screen buffer and moves cursor to the
+// home of screen (line 0, column 0).
+func (r *Dev) Reset() error {
+	if err := r.clearBits(); err != nil {
+		return err
+	}
+
+	delayMs(15)
+
+	if err := r.rsPin.Out(gpio.Low); err != nil {
+		return err
+	}
+	if err := r.enablePin.Out(gpio.Low); err != nil {
+		return err
+	}
+
+	if err := r.bulkSendData(resetSequence, r.write4Bits); err != nil {
+		return err
+	}
+
+	if err := r.bulkSendData(initSequence, r.writeInstruction); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *Dev) String() string {
+	return "HD44870, 4 bit mode"
+}
+
+// Halt clears the LCD screen
+func (r *Dev) Halt() error {
+	if err := r.writeInstruction(0x01); err != nil {
+		return err
+	}
+	delayMs(2)
+	return nil
+}
+
+// SetCursor positions the cursor
+//	line - screen line, 0-based
+//	column - column, 0-based
+func (r *Dev) SetCursor(line uint8, column uint8) error {
+	if err := r.writeInstruction(0x80 | (line*lineTwo + column)); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Print the data string
+//	data string to display
+func (r *Dev) Print(data string) error {
+	for _, v := range []byte(data) {
+		if err := r.WriteChar(v); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// WriteChar writes a single byte (character) at the cursor position.
+//	data - character code
+func (r *Dev) WriteChar(data uint8) error {
+	if err := r.sendData(); err != nil {
+		return err
+	}
+	if err := r.write4Bits(data >> 4); err != nil {
+		return err
+	}
+	if err := r.write4Bits(data); err != nil {
+		return err
+	}
+	delayUs(10)
+	return nil
+}
+
+// service methods
+
+var resetSequence = [][]uint{
+	{0x03, 50}, // init 1-st cycle
+	{0x03, 10}, // init 2-nd cycle
+	{0x03, 10}, // init 3-rd cycle
+	{0x02, 10}, // init finish
+}
+
+var initSequence = [][]uint{
+	{0x14, 0},    // 4-bit mode, 2 lines, 5x7 chars high
+	{0x10, 0},    // disable display
+	{0x01, 2000}, // clear screen
+	{0x06, 0},    // cursor shift right, no display move
+	{0x0c, 0},    // enable display no cursor
+	{0x01, 2000}, // clear screen
+	{0x02, 2000}, // cursor home
+}
+
+func (r *Dev) bulkSendData(seq [][]uint, f func(_data uint8) error) error {
+	for _, v := range seq {
+		if err := f(uint8(v[0])); err != nil {
+			return err
+		}
+		if v[1] > 0 {
+			delayUs(v[1])
+		}
+	}
+	return nil
+}
+
+func (r *Dev) clearBits() error {
+	for _, v := range r.dataPins {
+		if err := v.Out(gpio.Low); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (r *Dev) write4Bits(data uint8) error {
+	for i, v := range r.dataPins {
+		if data&(1<<uint(i)) > 0 {
+			if err := v.Out(gpio.High); err != nil {
+				return err
+			}
+		} else {
+			if err := v.Out(gpio.Low); err != nil {
+				return err
+			}
+		}
+	}
+	return r.strobe()
+}
+
+func (r *Dev) sendInstruction() error {
+	if err := r.rsPin.Out(gpio.Low); err != nil {
+		return err
+	}
+	if err := r.enablePin.Out(gpio.Low); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (r *Dev) sendData() error {
+	if err := r.rsPin.Out(gpio.High); err != nil {
+		return err
+	}
+	if err := r.enablePin.Out(gpio.Low); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (r *Dev) writeInstruction(data uint8) error {
+	if err := r.sendInstruction(); err != nil {
+		return err
+	}
+	// write high 4 bits
+	if err := r.write4Bits(data >> 4); err != nil {
+		return err
+	}
+	// write low  bits
+	if err := r.write4Bits(data); err != nil {
+		return err
+	}
+	delayUs(50)
+	return nil
+}
+
+func (r *Dev) strobe() error {
+	if err := r.enablePin.Out(gpio.High); err != nil {
+		return err
+	}
+	delayUs(2)
+	if err := r.enablePin.Out(gpio.Low); err != nil {
+		return err
+	}
+	return nil
+}
+
+func delayUs(ms uint) {
+	time.Sleep(time.Duration(ms) * time.Microsecond)
+}
+
+func delayMs(ms int) {
+	time.Sleep(time.Duration(ms) * time.Millisecond)
+}
+
+var _ conn.Resource = &Dev{}
+var _ fmt.Stringer = &Dev{}