mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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218 lines
7.5 KiB
C++
218 lines
7.5 KiB
C++
/*
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* © 2021, Neil McKechnie. All rights reserved.
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* Based on the work by DFRobot, Frank de Brabander and Marco Schwartz.
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*
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* This file is part of CommandStation-EX
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*
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* This is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* It is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with CommandStation-EX. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <Arduino.h>
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#include "LiquidCrystal_I2C.h"
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#include "I2CManager.h"
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// When the display powers up, it is configured as follows:
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//
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// 1. Display clear
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// 2. Function set:
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// DL = 1; 8-bit interface data
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// N = 0; 1-line display
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// F = 0; 5x8 dot character font
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// 3. Display on/off control:
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// D = 0; Display off
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// C = 0; Cursor off
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// B = 0; Blinking off
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// 4. Entry mode set:
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// I/D = 1; Increment by 1
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// S = 0; No shift
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//
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// Note, however, that resetting the Arduino doesn't reset the LCD, so we
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// can't assume that its in that state when a sketch starts (and the
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// LiquidCrystal constructor is called).
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LiquidCrystal_I2C::LiquidCrystal_I2C(uint8_t lcd_Addr, uint8_t lcd_cols,
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uint8_t lcd_rows) {
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_Addr = lcd_Addr;
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_cols = lcd_cols;
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_rows = lcd_rows;
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_backlightval = LCD_NOBACKLIGHT;
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}
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void LiquidCrystal_I2C::init() { init_priv(); }
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void LiquidCrystal_I2C::init_priv() {
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I2CManager.begin();
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I2CManager.setClock(100000L); // PCF8574 is spec'd to 100kHz.
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_displayfunction = LCD_4BITMODE | LCD_1LINE | LCD_5x8DOTS;
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begin(_cols, _rows);
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}
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void LiquidCrystal_I2C::begin(uint8_t cols, uint8_t lines) {
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if (lines > 1) {
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_displayfunction |= LCD_2LINE;
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}
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_numlines = lines;
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(void)cols; // Suppress compiler warning.
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// according to datasheet, we need at least 40ms after power rises above 2.7V
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// before sending commands. Arduino can turn on way befer 4.5V so we'll allow
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// 100 milliseconds after pulling both RS and R/W and backlight pin low
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expanderWrite(
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_backlightval); // reset expander and turn backlight off (Bit 8 =1)
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delay(100);
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// put the LCD into 4 bit mode
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// this is according to the hitachi HD44780 datasheet
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// figure 24, pg 46
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// we start in 8bit mode, try to set 4 bit mode
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write4bits(0x03 << 4);
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delayMicroseconds(4500); // wait min 4.1ms
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// second try
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write4bits(0x03 << 4);
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delayMicroseconds(4500); // wait min 4.1ms
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// third go!
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write4bits(0x03 << 4);
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delayMicroseconds(150);
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// finally, set to 4-bit interface
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write4bits(0x02 << 4);
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// set # lines, font size, etc.
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command(LCD_FUNCTIONSET | _displayfunction);
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// turn the display on with no cursor or blinking default
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_displaycontrol = LCD_DISPLAYON | LCD_CURSOROFF | LCD_BLINKOFF;
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display();
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// clear it off
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clear();
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// Initialize to default text direction (for roman languages)
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_displaymode = LCD_ENTRYLEFT | LCD_ENTRYSHIFTDECREMENT;
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// set the entry mode
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command(LCD_ENTRYMODESET | _displaymode);
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setCursor(0, 0);
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}
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/********** high level commands, for the user! */
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void LiquidCrystal_I2C::clear() {
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command(LCD_CLEARDISPLAY); // clear display, set cursor position to zero
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delayMicroseconds(2000); // this command takes 1.52ms
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}
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void LiquidCrystal_I2C::setCursor(uint8_t col, uint8_t row) {
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int row_offsets[] = {0x00, 0x40, 0x14, 0x54};
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if (row > _numlines) {
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row = _numlines - 1; // we count rows starting w/0
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}
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command(LCD_SETDDRAMADDR | (col + row_offsets[row]));
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}
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// Turn the display on/off (quickly)
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void LiquidCrystal_I2C::noDisplay() {
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_displaycontrol &= ~LCD_DISPLAYON;
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command(LCD_DISPLAYCONTROL | _displaycontrol);
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}
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void LiquidCrystal_I2C::display() {
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_displaycontrol |= LCD_DISPLAYON;
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command(LCD_DISPLAYCONTROL | _displaycontrol);
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}
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// Turn the (optional) backlight off/on
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void LiquidCrystal_I2C::noBacklight(void) {
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_backlightval = LCD_NOBACKLIGHT;
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expanderWrite(0);
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}
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void LiquidCrystal_I2C::backlight(void) {
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_backlightval = LCD_BACKLIGHT;
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expanderWrite(0);
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}
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size_t LiquidCrystal_I2C::write(uint8_t value) {
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send(value, Rs);
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return 1;
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}
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/*********** mid level commands, for sending data/cmds */
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inline void LiquidCrystal_I2C::command(uint8_t value) {
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send(value, 0);
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}
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/************ low level data pushing commands **********/
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/* According to the NXP Datasheet for the PCF8574 section 8.2:
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* "The master (microcontroller) sends the START condition and slave address
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* setting the last bit of the address byte to logic 0 for the write mode.
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* The PCF8574/74A acknowledges and the master then sends the data byte for
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* P7 to P0 to the port register. As the clock line goes HIGH, the 8-bit
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* data is presented on the port lines after it has been acknowledged by the
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* PCF8574/74A. [...] The master can then send a STOP or ReSTART condition
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* or continue sending data. The number of data bytes that can be sent
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* successively is not limited and the previous data is overwritten every
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* time a data byte has been sent and acknowledged."
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*
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* This driver takes advantage of this by sending multiple data bytes in succession
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* within a single I2C transmission. With a fast clock rate of 400kHz, the time
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* between successive updates of the PCF8574 outputs will be at least 2.5us. With
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* the default clock rate of 100kHz the time between updates will be at least 10us.
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*
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* The LCD controller HD44780, according to its datasheet, needs nominally 37us
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* (up to 50us) to execute a command (i.e. write to gdram, reposition, etc.). Each
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* command is sent in a separate I2C transmission here. The time taken to end a
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* transmission and start another one is a stop bit, a start bit, 8 address bits,
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* an ack, 8 data bits and another ack; this is at least 20 bits, i.e. >50us
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* at 400kHz and >200us at 100kHz. Therefore, we don't need additional delay.
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*
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* Similarly, the Enable must be set/reset for at least 450ns. This is
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* well within the I2C clock cycle time of 2.5us at 400kHz. Data is clocked in
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* to the HD44780 on the trailing edge of the Enable pin, so we set the Enable
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* as we present the data, then in the next byte we reset Enable without changing
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* the data.
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*/
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// write either command or data (8 bits) to the HD44780 LCD controller as
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// a single I2C transmission.
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void LiquidCrystal_I2C::send(uint8_t value, uint8_t mode) {
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mode |= _backlightval;
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uint8_t highnib = (value & 0xf0) | mode;
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uint8_t lownib = ((value << 4) & 0xf0) | mode;
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// Send both nibbles
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byte buffer[] = {(byte)(highnib|En), highnib, (byte)(lownib|En), lownib};
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I2CManager.write(_Addr, buffer, sizeof(buffer));
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}
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// write 4 bits to the HD44780 LCD controller.
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void LiquidCrystal_I2C::write4bits(uint8_t value) {
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uint8_t _data = value | _backlightval;
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// Enable must be set/reset for at least 450ns. This is well within the
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// I2C clock cycle time of 2.5us at 400kHz. Data is clocked in to the
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// HD44780 on the trailing edge of the Enable pin.
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byte buffer[] = {(byte)(_data|En), _data};
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I2CManager.write(_Addr, buffer, sizeof(buffer));
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}
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// write a byte to the PCF8574 I2C interface. We don't need to set
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// the enable pin for this.
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void LiquidCrystal_I2C::expanderWrite(uint8_t value) {
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I2CManager.write(_Addr, 1, value | _backlightval);
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} |