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LiquidCrystal_SR2W.h
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// ---------------------------------------------------------------------------
// Created/Adapted by Bill Perry 2012-03-16
// Copyright 2012 - Under creative commons license 3.0:
// Attribution-ShareAlike CC BY-SA
//
// This software is furnished "as is", without technical support, and with no
// warranty, express or implied, as to its usefulness for any purpose.
//
// @file LiquidCrystal_SR2W.h
// Connects a hd44780 LCD using 2 pins from the Arduino, via an 8-bit
// ShiftRegister (SR2W from now on).
//
// @brief
// This is the 2 wire shift register interface class for the LCD library
//
// The functionality provided by this class and its base class is a superset of
// the original functionality of the Arduino LiquidCrystal library and can
// be used as such.
// See the LCD class for a full description of the API functions available.
//
// It works with a 8-bit unlatched, no-tristate, unidirectional SIPO (Serial-In-Parallel-Out)
// shift register (IE a very simple SR), and an hd44780 LCD in 4-bit mode.
// Any such shift register should do (pref. 74LS family IC's for 2-wire).
// 74LS164 and 74HC595 have been exstensively tested.
//
//
// 2 Pins required from the Arduino:
// - Data/Enable
// - Clock
// The Data pin is also used to control the enable signal
// LCD RW-pin hardwired to LOW (only writing to LCD).
// Busy Flag (BF, data bit D7) is not read.
//
// Original project homepage: http://code.google.com/p/arduinoshiftreglcd/
//
// Shift register bits
// Bit #0 - (cannot be used on 74HC595)
// Bit #1 - optional backlight control
// Bit #2 - connects to RS (Register Select) on the LCD
// Bit #3 - connects to LCD data inputs D4
// Bit #4 - connects to LCD data inputs D5
// Bit #5 - connects to LCD data inputs D6
// Bit #6 - connects to LCD data inputs D7
// Bit #7 - enables the LCD enable-puls (via the diode-resistor AND "gate")
//
// Wiring for a 74LS164
// ---------------------
// 1k/4.7k
// +--------[ Resistor ]--------+---(LCD Enable)
// | |
// | 74LS164 (VCC) |
// | +----u----+ | _V_ diode
// (data pin)---+---+--1-|A VCC|-14-+ |
// | | | |
// +--2-|B Q7|-13------+
// 3-|Q0 Q6|-12--(LCD D7)
// (BL Circuit)--------4-|Q1 Q5|-11--(LCD D6)
// (LCD RS)------------5-|Q2 Q4|-10--(LCD D5)
// (LCD D4)------------6-|Q3 /MR|--9--(VCC)
// +-7-|GND CP|--8--(clock pin)
// | +---------+
// | 0.1uf
// (gnd)-----||----(vcc)
//
// Wiring for a 74HC595
// --------------------
// NOTE: the 74HC595 is a latching shift register. In order to get it to operate
// in a "non latching" mode, RCLK and SCLK are tied together. The side effect of this
// is that the latched output is one clock behind behind the internal shift register bits.
// To compensate for this the wiring is offset by one bit position lower.
// For example, while the backlight is hooked to Q0 it is still using bit 1 of
// of the shift register because the outputs are 1 clock behind the real internal shift
// register.
//
// 74HC595 (VCC)
// +----u----+ | +-----------------------(BL circuit)
// (LCD RS)------------1-|Q1 VCC|-16-+ | +--------------------(data pin)
// (LCD D4)------------2-|Q2 Q0|-15----+ | 1k/4.7k
// (LCD D5)------------3-|Q3 SER|-14-------+---[ Resistor ]--+--(LCD Enable)
// (LCD D6)------------4-|Q4 /OE|-13--(gnd) |
// (LCD D7)------------5-|Q5 RCLK|-12-------+ |
// | | | |
// +------6-|Q6 SCLK|-11-------+--(clock pin) |
// | 7-|Q7 /MR|-10--(VCC) |
// | +-8-|GND Q6'|--9 |
// | | +---------+ diode _V_
// | | 0.1uf |
// | (gnd)-----||----(vcc) |
// +-----------------------------------------------+
//
//
// Backlight Control circuit
// -------------------------
// Because the shift resiter is not latching the outputs, the backlight circuitry
// will "see" the output bits as they are shifted into the shift register which
// can cause the backlight to flicker rather than remain constantly on/off.
// The circuit below slows down the transitions to the transistor to remove
// the visible flicker. When the BL input is HIGH the LCD backlight will turn on.
//
// (value depends on LCD, 100ohm is usually safe)
// (LCD BL anode)---[ resistor ]---(vcc)
//
// (LCD BL cathode)-------------------------------+
// |
// D
// |
// (BL input)----[ 4.7k Resistor ]----+-------G-|-< (2N7000 FET)
// | |
// (0.1uf) = S
// | |
// (gnd) (gnd)
//
//
//
//
// History
// 2012.03.16 bperrybap - creation/adaption from SR header to create SR2W header.
// Fixed typo in SR2W mask define names
// @author B. Perry - [email protected]
// --------------------------------------------------------------------------------
#ifndef _LIQUIDCRYSTAL_SR2W_
#define _LIQUIDCRYSTAL_SR2W_
#include <inttypes.h>
#include "LCD.h"
#include "FastIO.h"
// two-wire SR output bit constants
// ---------------------------------------------------------------------------
#define SR2W_BL_MASK 0x02
#define SR2W_RS_MASK 0x04
#define SR2W_DATA_MASK 0x78 // data bits are hard coded to be SR bits 6,5,4,3
#define SR2W_EN_MASK 0x80 // cannot ever be changed
class LiquidCrystal_SR2W : public LCD
{
public:
/*!
@method
@abstract LCD 2 wire SHIFT REGISTER constructor.
@discussion Defines the pin assignments that connect to the shift register.
The constructor does not initialize the LCD. Assuming 1 line 8 pixel high
font.
@param srdata[in] Arduino pin for shift register data line.
@param srclock[in] Arduino pin for shift register clock line.
@param blpol[in] optional backlight polarity (default = POSITIVE)
*/
LiquidCrystal_SR2W (uint8_t srdata, uint8_t srclock, t_backlighPol blpol = POSITIVE);
/*!
@function
@abstract Send a particular value to the LCD.
@discussion Sends a particular value to the LCD for writing to the LCD or
as an LCD command using the shift register.
Users should never call this method.
@param value[in] Value to send to the LCD.
@param mode[in] DATA=8bit data, COMMAND=8bit cmd, FOUR_BITS=4bit cmd
the LCD.
*/
virtual void send(uint8_t value, uint8_t mode);
/*!
@function
@abstract Switch-on/off the LCD backlight.
@discussion Switch-on/off the LCD backlight.
The setBacklightPin has to be called before setting the backlight for
this method to work. @see setBacklightPin.
@param mode[in] backlight mode (0 off, non-zero on)
*/
void setBacklight ( uint8_t mode );
private:
/*!
@method
@abstract Initializes the LCD pin allocation
@discussion Initializes the LCD pin allocation and configuration.
*/
void init ( uint8_t srdata, uint8_t srclock, t_backlighPol blpol, uint8_t lines, uint8_t font );
/*!
* @method
* @abstract takes care of shifting and the enable pulse
*/
void loadSR (uint8_t val);
fio_register _srDataRegister; // Serial Data pin
fio_bit _srDataMask;
fio_register _srClockRegister; // Clock Pin
fio_bit _srClockMask;
uint8_t _blPolarity;
uint8_t _blMask;
};
#endif