Merge pull request #27 from uutzinger/master

Enable using non-default i2c port.
New example.

Author: mathertel

examples/LCD_Burnin/LCD_Burnin.ino

@@ -0,0 +1,49 @@
+// LCD with i2c backpack test
+// This replaces the contents of an LCD screen with the contents of a buffer
+// Urs Utzinger, 2020
+
+#include "LiquidCrystal_PCF8574.h"
+#include <Wire.h>
+
+TwoWire Wire_1 = TwoWire();
+
+LiquidCrystal_PCF8574 lcd(0x27);  // set the LCD address to 0x27 
+char lcdDisplay[4][20];           // 4 lines of 20 character buffer
+
+void setup()
+{
+  Wire_1.begin(D1, D2);  // custom i2c port on ESP
+  Wire_1.setClock(100000); // standard 100kHz speed
+  Wire_1.setClockStretchLimit(200000); // some devices might need clock stretching
+  lcd.begin(20,4, Wire_1);
+  lcd.setBacklight(255);
+}
+
+void loop()
+{
+  char lcdbuf[21];
+  const char someLine[] = "0123456789ABCDEF1234";  // 20 chars
+  
+  // fill the screen buffer
+  strncpy(&lcdDisplay[0][0], someLine , 20);
+  strncpy(&lcdDisplay[1][0], someLine , 20);
+  strncpy(&lcdDisplay[2][0], someLine , 20);
+  strncpy(&lcdDisplay[3][0], someLine , 20);
+  // prepare screen
+  lcd.home();
+  lcd.clear();
+  lcd.setCursor(0, 0);   
+  // copy the buffer to the screen
+  // 1st line continues at 3d line
+  // 2nd line continues at 4th line
+  strncpy(lcdbuf, &lcdDisplay[0][0], 20); lcdbuf[20] = '\0'; // create a termineted text line 
+  lcd.print(lcdbuf);                                         // print the line to screen
+  strncpy(lcdbuf, &lcdDisplay[2][0], 20); lcdbuf[20] = '\0';
+  lcd.print(lcdbuf); 
+  strncpy(lcdbuf, &lcdDisplay[1][0], 20); lcdbuf[20] = '\0';
+  lcd.print(lcdbuf); 
+  strncpy(lcdbuf, &lcdDisplay[3][0], 20); lcdbuf[20] = '\0';
+  lcd.print(lcdbuf);
+
+  delay(50); // keep artifically short to test if screen corrupts with frequent writes
+}

src/LiquidCrystal_PCF8574.cpp

@@ -56,8 +56,10 @@ void LiquidCrystal_PCF8574::init(uint8_t i2cAddr, uint8_t rs, uint8_t rw, uint8_
 } // init()
 
 
-void LiquidCrystal_PCF8574::begin(uint8_t cols, uint8_t lines)
+void LiquidCrystal_PCF8574::begin(uint8_t cols, uint8_t lines, TwoWire &wirePort)
 {
+  _i2cPort = &wirePort; //Grab which port the user wants us to use
+
   _cols = min(cols, (uint8_t)80);
   _lines = min(lines, (uint8_t)4);
 
@@ -73,7 +75,7 @@ void LiquidCrystal_PCF8574::begin(uint8_t cols, uint8_t lines)
   }
 
   // initializing the display
-  Wire.begin();
+  _i2cPort->begin();
   _write2Wire(0x00, LOW, false);
   delayMicroseconds(50000);
 
@@ -245,7 +247,7 @@ void LiquidCrystal_PCF8574::setBacklight(uint8_t brightness)
 
 // Allows us to fill the first 8 CGRAM locations
 // with custom characters
-void LiquidCrystal_PCF8574::createChar(uint8_t location, byte charmap[])
+void LiquidCrystal_PCF8574::createChar(uint8_t location, uint8_t charmap[])
 {
   location &= 0x7; // we only have 8 locations 0-7
   // Set CGRAM address
@@ -259,12 +261,12 @@ void LiquidCrystal_PCF8574::createChar(uint8_t location, byte charmap[])
 #ifdef __AVR__
 // Allows us to fill the first 8 CGRAM locations
 // with custom characters stored in PROGMEM
-void LiquidCrystal_PCF8574::createChar_P(uint8_t location, const byte *charmap) {
+void LiquidCrystal_PCF8574::createChar_P(uint8_t location, const uint8_t *charmap) {
   PGM_P p = reinterpret_cast<PGM_P>(charmap);
   location &= 0x7; // we only have 8 locations 0-7
   _send(0x40 | (location << 3));
   for (int i = 0; i < 8; i++) {
-    byte c = pgm_read_byte(p++);
+    uint8_t c = pgm_read_byte(p++);
     write(c);
   }
 } // createChar_P()
@@ -285,12 +287,12 @@ void LiquidCrystal_PCF8574::_send(uint8_t value, bool isData)
   // An I2C transmission has a significant overhead of ~10+1 I2C clock
   // cycles. We consequently only perform it only once per _send().
 
-  Wire.beginTransmission(_i2cAddr);
+  _i2cPort->beginTransmission(_i2cAddr);
   // write high 4 bits
   _writeNibble((value >> 4 & 0x0F), isData);
   // write low 4 bits
   _writeNibble((value & 0x0F), isData);
-  Wire.endTransmission();
+  _i2cPort->endTransmission();
 } // _send()
 
 
@@ -317,19 +319,19 @@ void LiquidCrystal_PCF8574::_writeNibble(uint8_t halfByte, bool isData)
   // when the I2C bus is operated beyond the chip's spec in fast mode
   // at 400 kHz.
 
-  Wire.write(data | _enable_mask);
+  _i2cPort->write(data | _enable_mask);
   // delayMicroseconds(1); // enable pulse must be >450ns
-  Wire.write(data);
+  _i2cPort->write(data);
   // delayMicroseconds(37); // commands need > 37us to settle
 } // _writeNibble
 
 
 // write a nibble / halfByte with handshake
 void LiquidCrystal_PCF8574::_sendNibble(uint8_t halfByte, bool isData)
 {
-  Wire.beginTransmission(_i2cAddr);
+  _i2cPort->beginTransmission(_i2cAddr);
   _writeNibble(halfByte, isData);
-  Wire.endTransmission();
+  _i2cPort->endTransmission();
 } // _sendNibble
 
 
@@ -344,9 +346,9 @@ void LiquidCrystal_PCF8574::_write2Wire(uint8_t data, bool isData, bool enable)
   if (_backlight > 0)
     data |= _backlight_mask;
 
-  Wire.beginTransmission(_i2cAddr);
-  Wire.write(data);
-  Wire.endTransmission();
+  _i2cPort->beginTransmission(_i2cAddr);
+  _i2cPort->write(data);
+  _i2cPort->endTransmission();
 } // write2Wire
 
 // The End.

src/LiquidCrystal_PCF8574.h

@@ -27,6 +27,7 @@
 #define LiquidCrystal_PCF8574_h
 
 #include "Arduino.h"
+#include <Wire.h>	
 #include "Print.h"
 #include <stddef.h>
 #include <stdint.h>
@@ -37,8 +38,27 @@ class LiquidCrystal_PCF8574 : public Print
 public:
   LiquidCrystal_PCF8574(uint8_t i2cAddr);
   // note:
-  // There is no sda and scl parameter for i2c in any api.
-  // The Wire library has standard settings that can be overwritten by using Wire.begin(int sda, int scl) before calling LiquidCrystal_PCF8574::begin();
+  //
+	// When using multiple I2C ports one can initialize with
+  //   LiquidCrystal_PCF8574 lcd(0x27);     // create lcd
+  //   TwoWire myWire = TwoWire();          // create new wire instance
+  //   myWire.begin(sdaPin, sclPin);        // define SDA and SCL pins
+  //   myWire.setClock(100000);             // I2C speed 100kHz
+  //   myWire.setClockStretchLimit(200000); // I2C clock stretch to 200ms for slow devices
+  //   lcd_port = &myWire;                  // Keep address to wire instance
+  //   lcd.begin(clos, rows, *lcd_port);    // Initialize lcd
+  //
+  // and in the main program one updates display with
+  //   # if defined(ESP8266)
+  //     ESP8266 is special case because there is only one wire structure available
+  //     Although we can created multiple wire interfaces we still need to specify SDA and SCL 
+  //     before each transmission:
+  //     lcd_port->begin(sdaPin, sclPin);     
+  //     lcd_port->setClock(100000);
+  //     lcd_port->setClockStretchLimit(200000); // 200ms, for slow devices
+  //   # endif
+  //   lcd.setCursor(0, 0); 
+  //   lcd.print(lcdbuf);
 
   // constructors, which allow to redefine bit assignments in case your adapter is wired differently
   LiquidCrystal_PCF8574(uint8_t i2cAddr, uint8_t rs, uint8_t enable,
@@ -48,7 +68,7 @@ class LiquidCrystal_PCF8574 : public Print
 
   // Functions from reference:
 
-  void begin(uint8_t cols, uint8_t rows);
+  void begin(uint8_t cols, uint8_t rows, TwoWire &wirePort = Wire);
 
   void clear();
   void home();
@@ -65,10 +85,10 @@ class LiquidCrystal_PCF8574 : public Print
   void noAutoscroll();
   void leftToRight();
   void rightToLeft();
-  void createChar(uint8_t, byte[]);
+  void createChar(uint8_t location, uint8_t charmap[]);
 #ifdef __AVR__
-  void createChar_P(uint8_t, const byte *);
-  inline void createChar(uint8_t n, const byte *data) {
+  void createChar_P(uint8_t, const uint8_t *);
+  inline void createChar(uint8_t n, const uint8_t *data) {
     createChar_P(n, data);
   };
 #endif
@@ -81,6 +101,9 @@ class LiquidCrystal_PCF8574 : public Print
   virtual size_t write(uint8_t ch);
 
 private:
+
+  TwoWire *_i2cPort; //The generic connection to user's chosen I2C hardware
+
   // instance variables
   uint8_t _i2cAddr; ///< Wire Address of the LCD
   uint8_t _backlight; ///< the backlight intensity