lcd1602.cpp

//
// 2x16 LCD display (HD44780 controller + I2C chip)
//
// Copyright (c) BitBank Software, Inc.
// Written by Larry Bank
// bitbank@pobox.com
// Project started 12/6/2017
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
#include <Arduino.h>
#include <Wire.h>
#include <lcd1602.h>

//
// The LCD controller is wired to the I2C port expander with the upper 4 bits
// (D4-D7) connected to the data lines and the lower 4 bits (D0-D3) used as
// control lines. Here are the control line definitions:
//
// Command (0) / Data (1) (aka RS) (D0)
// R/W                             (D1)
// Enable/CLK                      (D2) 
// Backlight control               (D3)
//
// The data must be manually clocked into the LCD controller by toggling
// the CLK line after the data has been placed on D4-D7
//
#define PULSE_PERIOD 500
#define CMD_PERIOD 4100

#define BACKLIGHT 8
#define DATA 1
static int iBackLight = BACKLIGHT;
static int iLCDAddr;

// Wrapper function to write I2C data on Arduino
static void I2CWrite(int iAddr, unsigned char *pData, int iLen)
{
  Wire.beginTransmission(iAddr);
  Wire.write(pData, iLen);
  Wire.endTransmission();
} /* I2CWrite() */

static void WriteCommand(unsigned char ucCMD)
{
unsigned char uc;

  uc = (ucCMD & 0xf0) | iBackLight; // most significant nibble sent first
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(PULSE_PERIOD); // manually pulse the clock line
  uc |= 4; // enable pulse
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(PULSE_PERIOD);
  uc &= ~4; // toggle pulse
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(CMD_PERIOD);
  uc = iBackLight | (ucCMD << 4); // least significant nibble
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(PULSE_PERIOD);
  uc |= 4; // enable pulse
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(PULSE_PERIOD);
  uc &= ~4; // toggle pulse
  I2CWrite(iLCDAddr, &uc, 1);
  delayMicroseconds(CMD_PERIOD);

} /* WriteCommand() */

//
// Control the backlight, cursor, and blink
// The cursor is an underline and is separate and distinct
// from the blinking block option
//
void lcd1602Control(int bBacklight, int bCursor, int bBlink)
{
unsigned char ucCMD = 0xc; // display control

  iBackLight = (bBacklight) ? BACKLIGHT : 0;
  if (bCursor)
    ucCMD |= 2;
  if (bBlink)
    ucCMD |= 1;
  WriteCommand(ucCMD);
} /* lcd1602Control() */

//
// Write an ASCII string (up to 16 characters at a time)
// 
int lcd1602WriteString(char *text)
{
unsigned char ucTemp[2];
int i = 0;

  if (text == NULL)
    return 1;

  while (i<16 && *text)
  {
    ucTemp[0] = iBackLight | DATA | (*text & 0xf0);
    I2CWrite(iLCDAddr, ucTemp, 1);
    delayMicroseconds(PULSE_PERIOD);
    ucTemp[0] |= 4; // pulse E
    I2CWrite(iLCDAddr, ucTemp, 1);
    delayMicroseconds(PULSE_PERIOD);
    ucTemp[0] &= ~4;
    I2CWrite(iLCDAddr, ucTemp, 1);
    delayMicroseconds(PULSE_PERIOD);
    ucTemp[0] = iBackLight | DATA | (*text << 4);
    I2CWrite(iLCDAddr, ucTemp, 1);
    ucTemp[0] |= 4; // pulse E
    I2CWrite(iLCDAddr, ucTemp, 1);
    delayMicroseconds(PULSE_PERIOD);
    ucTemp[0] &= ~4;
    I2CWrite(iLCDAddr, ucTemp, 1);
    delayMicroseconds(CMD_PERIOD);
    text++;
    i++;
  }
  return 0;
} /* WriteString() */

//
// Erase the display memory and reset the cursor to 0,0
//
void lcd1602Clear(void)
{
  WriteCommand(0x0E); // clear the screen
} /* lcd1602Clear() */

//
// Configure and power up the display
//
void lcd1602Powerup()
{
  WriteCommand(0x02); // Set 4-bit mode of the LCD controller
  WriteCommand(0x28); // 2 lines, 5x8 dot matrix
  WriteCommand(0x0c); // display on, cursor off
  WriteCommand(0x06); // inc cursor to right when writing and don't scroll
  WriteCommand(0x80); // set cursor to row 1, column 1
}
//
// Open a file handle to the I2C device
// Set the controller into 4-bit mode and clear the display
// returns 0 for success, 1 for failure
//
void lcd1602Init(int iAddr)
{
  iLCDAddr = iAddr;
  iBackLight = BACKLIGHT; // turn on backlight
  Wire.begin(); // Initiate the Wire library
  Wire.setClock(400000); // use high speed I2C mode (default is 100Khz)
  lcd1602Powerup();
  lcd1602Clear();     // clear the memory
} /* lcd1602Init() */

//
// Set the LCD cursor position
//
int lcd1602SetCursor(int x, int y)
{
unsigned char cCmd;

  if (x < 0 || x > 15 || y < 0 || y > 1)
    return 1;

  cCmd = (y==0) ? 0x80 : 0xc0;
  cCmd |= x;
  WriteCommand(cCmd);
  return 0;

} /* lcd1602SetCursor() */

void lcd1602Shutdown(void)
{
  iBackLight = 0; // turn off backlight
  WriteCommand(0x08); // turn off display, cursor and blink 
} /* lcd1602Shutdown() */