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LiquidCrystal_SR1W.h
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LiquidCrystal_SR1W.h
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// ---------------------------------------------------------------------------
// Created/Adapted by Stephen Erisman 2013-07-06
// Copyright (C) - 2018
//
// 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
// 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 v3.0
// along with this program.
// If not, see <https://www.gnu.org/licenses/gpl-3.0.en.html>.
//
// ---------------------------------------------------------------------------
//
// @file LiquidCrystal_SR1W.h
// Connects a hd44780 LCD using 1 pin from the Arduino, via an 8-bit Latching
// ShiftRegister (SR1W from now on).
//
// @brief
// This is the 1 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 latched, no-tristate, unidirectional SIPO (Serial-In-Parallel-Out)
// shift register, and an hd44780 LCD in 4-bit mode.
// The 74HC595 shift register has been tested.
//
//
// 1 Pin required from the Arduino:
// - Serial PIN:
// The Serial PIN is wired directly to the shift register's Clock PIN and its
// unaltered signal directly triggers the Clock on every LOW to HIGH transition.
//
// Additionally, the Serial PIN is wired through a resistor capacitor (RC) filter to
// the shift register's Data PIN. During a quick transition of the Serial PIN the
// RC filter will maintain the Data PIN's previous value because the capacitor isn't
// given enough time to charge (or discharge) to the alternate state. If the transition
// is held for enough time, however, the RC capacitor will charge (or discharge) and the
// value seen by the Data PIN will have changed state.
//
// There are two circuit versions that behave differently for Latch, Enable, and Clear:
//
// HW_CLEAR version:
// In this version the shift register's Latch and LCD's Enable PINs are wired directly to
// the shift register's Q'H output. The shift register's /Clear PIN is then wired up
// through two logic "gates": first QH and Q'H are AND'd together with a diode-resistor
// "gate" the output of which is NAND'd with VCC using a resistor-NPN-resistor "gate".
// So, /CLR = ((QH AND Q'H) NAND VCC). We also put a capacitor on the NPN base to GND
// to delay the signal a bit and allow the Latch and EN signals some extra time to trigger.
//
// This all fits together as follows:
// 1. We shift in a '1'.
// 2. Ws shift in the other 7 bits.
// 3. At this point the first '1' has been shifted into Q'H causing it to go HIGH.
// 4. When Q'H is HIGH it causes Latch and EN to also go HIGH.
// 5. When Latch transitions to HIGH it changes the shift register outputs to the bits
// that were shifted in.
// 6. This causes QH to go HIGH (if it wasn't already).
// 7. Now that QH AND Q'H are both HIGH they causes the base capacitor to start charging.
// 8. When the capacitor has charged enough the transistor brings /CLR LOW.
// 8. This will cause /CLR to trigger and the shift register will be cleared
// (NOTE: This doesn't change the latched outputs)
// 9. The clearing of the shift register causes Q'H to go LOW.
// 9. When Q'H is LOW it causes Latch and EN to also go LOW.
// 10. When EN transitions to LOW the LCD reads in the bits on the shift register pins
// and does it's thing.
// 11. Now that Q'H is LOW the base capacitor starts discharging.
// 12. When the capacitor has discharged enough the transistor will stop sinking /CLR.
// 13. This will cause /CLR to be pulled back up to HIGH by the VCC pullup resistor
// (it will stay that way until our next nibble/byte has been shifted in)
// 14. We are now ready for our next nibble/byte.
//
//
// SW_CLEAR version:
// In this version the Serial PIN is wired to the shift register's Latch and LCD's Enable
// PINs through another RC filter. These PINs are also wired through a diode (AND "gate")
// tied to the shift register's Q'H output. This combination means that the Latch and
// Enable PINs will be held LOW as long as EITHER the Q'H or RC output is LOW.
//
// This all fits together as follows:
// 1. We shift in a '1'.
// 2. We shift in the other 7 bits. (NOTE: We leave Serial PIN HIGH at the end of this)
// 3. At this point the first '1' has been shifted into Q'H causing it to go HIGH.
// (NOTE: Up until this time Q'H has been LOW so the attached diode has been keeping
// the Latch/EN pins LOW.)
// 4. Now that Q'H is HIGH it causes the attached diode to stop discharging the Latch/EN
// capacitor. We delay here for a while to make sure it is fully charged.
// 5. When the capacitor has charged enough Latch/EN will be HIGH
// 5. When Latch transitions to HIGH it changes the shift register outputs to what was
// shifted in.
// 6. We now bring the Serial PIN LOW and wait for the Latch/EN capacitor to discharge.
// 7. When the capacitor has discharged enough Latch/EN will be LOW
// 8. When EN transitions to LOW the LCD reads in the bits on the shift register pins
// and does it's thing.
// 9. We now shift in '0' 8 times (as quickly as possible).
// 10. If we keep the LOW to HIGH to LOW pulses short enough while shifting in the '0's
// the Latch/EN capacitor won't have time to charge to a point where it will re-trigger
// the Latch/EN pins.
// 11. Now Q'H will be LOW and the shift register has been cleared (NOTE: This doesn't
// change the latched outputs.)
// 12. We now bring the Serial PIN HIGH again and wait for the Data capacitor to recharge.
// 13. When the Data capacitor has fully charged we are ready for our next nibble/byte.
//
//
// These designs incorporate (and merge) ideas originally found here (1-wire concept):
// http://www.romanblack.com/shift1.htm
// and here (diode-resistor AND "gate" EN control):
// http://www.rentron.com/Myke1.htm
// as well as introducing some new and original ideas (particularly how HW_CLEAR works).
//
// Because of its use of the diode AND "gate", the SW_CLEAR design allows for faster sending
// of data to the LCD compared to Roman's original design. With the proposed 5uS delay (see
// notes below), a byte can be sent to the LCD in as little as 30 uS (plus overhead) when
// sending all 1's. This increases to as much as 190 uS (plus overhead) when sending all 0's.
// This is in comparison to Roman's estimate of around 3-4 mS to send a byte. So this
// implementation is 15-133 times faster for the cost of a single (1N4148 or similar) diode.
//
// The HW_CLEAR version is even faster as it can completely eliminate the clearSR() call as
// well as the delays that are needed to latch the data in the SW_CLEAR version.
//
//
// Default Shift Register Bits - Shifted MSB first:
// Bit #0 (QA) - not used
// Bit #1 (QB) - connects to LCD data input D7
// Bit #2 (QC) - connects to LCD data input D6
// Bit #3 (QD) - connects to LCD data input D5
// Bit #4 (QE) - connects to LCD data input D4
// Bit #5 (QF) - optional backlight control
// Bit #6 (QG) - connects to RS (Register Select) on the LCD
// Bit #7 (QH) - used for /CLR on the HW_CLEAR version (cannot be changed)
// (Q'H) - used for Latch/EN (via the diode AND "gate") (cannot be changed)
//
// NOTE: Any of these can be changed around as needed EXCEPT Bit #7 (QH and Q'H).
//
//
// Circuit Types (for the 74HC595)
// -------------------------------
// The 74HC595 is a latching shift register. See the explanations above for how these circuits
// work.
//
//
// HW_CLEAR version: (Faster but higher part count)
// ------------------------------------------------
//
// 74HC595 (VCC)
// +----u----+ | 2.2nF
// (LCD D7)------------1-|QB VCC|-16--+ +----||----(GND)
// (LCD D6)------------2-|QC QA|-15 |
// (LCD D5)------------3-|QD SER|-14-------+--[ Resistor ]--+
// (LCD D4)------------4-|QE /OE|-13--(GND) 1.5k |
// (BL Circuit)--------5-|QF RCK|-12-----+ |
// | | \ |
// (LCD RS)------------6-|QG SCK|-11-------)----------------+--(Serial PIN)
// | | |
// +-------7-|QH /CLR|-10-------)--+--[ Resistor ]--(VCC)
// | | | / | 1k
// | +--8-|GND Q'H|--9-----+ |
// | | +---------+ | | (GND)--(LCD RW)
// | | 0.1uF | \
// | (GND)-----||----(VCC) +------)--------------(LCD EN)
// | | /
// |----|<|----+--[ Resistor ]--| |
// diode | 1k C
// | |
// +-------------+---B-|> (NPN)
// | |
// (2.2nF) = E
// | |
// (GND) (GND)
//
//
// SW_CLEAR version: (Lower part count but slower)
// -----------------------------------------------
//
// 74HC595 (VCC)
// +----u----+ | 2.2nF
// (LCD D7)------------1-|QB VCC|-16--+ +----||----(GND)
// (LCD D6)------------2-|QC QA|-15 |
// (LCD D5)------------3-|QD SER|-14---------+--[ Resistor ]--+
// (LCD D4)------------4-|QE /OE|-13--(GND) 1.5k |
// (BL Circuit)--------5-|QF RCK|-12---------+ |
// | | \ |
// (LCD RS)------------6-|QG SCK|-11-----------)--------------+--(Serial PIN)
// 7-|QH /CLR|-10--(VCC) / |
// +--8-|GND Q'H|--9---|<|---+--[ Resistor ]--+
// | +---------+ diode | 1.5k
// | |
// | 0.1uF |
// (GND)-----||----(VCC) +----||----(GND)
// | 2.2nF
// (LCD EN)-------------------------------------+
// (LCD RW)--(GND)
//
//
// In either case the LCD RW pin is hardwired to GND meaning we will only be able to write
// to the LCD.
// Therefore, the Busy Flag (BF, data bit D7) is not able to be read and we have to make use
// of the minimum delay time constraints. This isn't really a problem because it usually
// takes us longer to shift and latch the data than the minimum delay anyway. For now, we
// simply keep track of our delays and add more delay at the end to get to at least 37 uS.
//
//
// Backlight Control Circuit
// -------------------------
// Since we are using the latching nature of the shift resiter we don't need the extra
// backlight circuitry that SR2W uses. Keeping it around, however, would still work because
// the circuit just slows down the transitions to the mosfet a bit.
//
// Here are two more optimized versions that can be used.
//
//
// NPN Transistor version: (Cheaper but more power draw and higher part count)
// ---------------------------------------------------------------------------
//
// (value depends on LCD, 100ohm is usually safe)
// (LCD BL anode)---[ resistor ]---(VCC)
//
// (LCD BL cathode)---------------+
// |
// C
// |
// (BL input)--[ Resistor ]---B-|> (NPN)
// 1k |
// E
// |
// (GND)
//
// NOTE: The Bate resistor is needed because the NPN is current fed. For lower
// power draw, try a 10k resistor.
//
//
// N-CH Mosfet version: (More costly but less power draw and lower part count)
// ---------------------------------------------------------------------------
//
// (value depends on LCD, 100ohm is usually safe)
// (LCD BL anode)---[ resistor ]---(VCC)
//
// (LCD BL cathode)---------------+
// |
// D
// |
// (BL input)----------------G-|-< (2N7000 FET)
// |
// S
// |
// (GND)
//
// NOTE: Gate resistor not needed because the mosfet is voltage fed and only really
// pulls current while switching.
//
// In either case, when the BL input is HIGH the LCD backlight will turn on.
//
//
// History
// 2013.07.31 serisman - fixed potential interrupt bug and made more performance optimizations
// 2013.07.10 serisman - more performance optimizations and modified the HW_CLEAR circuit a bit
// 2013.07.09 serisman - added an even faster version that performs the clear in hardware
// 2013.07.08 serisman - changed code to shift data MSB first to match SR2W
// 2013.07.07 serisman - major speed optimization
// 2013.07.06 serisman - created/modified from SR2W source to create SR1W
// @author S. Erisman - [email protected]
// --------------------------------------------------------------------------------
#ifndef _LIQUIDCRYSTAL_SR1W_
#define _LIQUIDCRYSTAL_SR1W_
#if defined (__AVR__)
#include <inttypes.h>
#include "LCD.h"
#include "FastIO.h"
// 1-wire SR timing constants
// ---------------------------------------------------------------------------
// NOTE:
// The 1.5k resistor (1.2k - 1.8k with a 20% tolerance)
// takes between 2.376uS and 4.36uS to fully charge or discharge
// the 2.2n capacitor (1.98n - 2.42n with a 10% tolerance).
// We round this up to a 5uS delay to provide an additional safety margin.
#define SR1W_DELAY_US 5
#define SR1W_DELAY() { delayMicroseconds(SR1W_DELAY_US); numDelays++; }
// 1-wire SR output bit constants
// ---------------------------------------------------------------------------
#define SR1W_UNUSED_MASK 0x01 // Set unused bit(s) to '1' as they are slightly faster to clock in.
#define SR1W_D7_MASK 0x02
#define SR1W_D6_MASK 0x04
#define SR1W_D5_MASK 0x08
#define SR1W_D4_MASK 0x10
#define SR1W_BL_MASK 0x20
#define SR1W_RS_MASK 0x40
#define SR1W_EN_MASK 0x80 // This cannot be changed. It has to be the first thing shifted in.
#define SR1W_ATOMIC_WRITE_LOW(reg, mask) ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { *reg &= ~mask; }
#define SR1W_ATOMIC_WRITE_HIGH(reg, mask) ATOMIC_BLOCK(ATOMIC_RESTORESTATE) { *reg |= mask; }
typedef enum { SW_CLEAR, HW_CLEAR } t_sr1w_circuitType;
class LiquidCrystal_SR1W : public LCD
{
public:
/*!
@method
@abstract LCD 1 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.
@param circuitType[in] optionally select an alternate circuit type
@param blpol[in] optional backlight polarity (default = POSITIVE)
*/
LiquidCrystal_SR1W (uint8_t srdata, t_sr1w_circuitType circuitType,
t_backlightPol 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, t_sr1w_circuitType circuitType, t_backlightPol blpol,
uint8_t lines, uint8_t font );
/*!
@method
@abstract Clears the shift register to ensure the Latch/Enable pins aren't
triggered accidentally.
*/
uint8_t clearSR ();
/*!
* @method
* @abstract takes care of shifting and the enable pulse
*/
uint8_t loadSR (uint8_t val);
fio_register _srRegister; // Serial PIN
fio_bit _srMask;
t_sr1w_circuitType _circuitType;
uint8_t _blPolarity;
uint8_t _blMask;
};
#else
#error "ONLY SUPPORTED ON AVR PROCESSORS"
#endif // defined (__AVR__)
#endif