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libraries/hd44780/examples/ioClass/hd44780_I2Cexp/ReadWrite/ReadWrite.ino

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+// vi:ts=4
+// ----------------------------------------------------------------------------
+// ReadWrite - simple demonstration reading data from LCD
+// Created by Bill Perry 2016-08-19
+// bperrybap@opensource.billsworld.billandterrie.com
+//
+// This example code is unlicensed and is released into the public domain
+// ----------------------------------------------------------------------------
+// 
+// This sketch is for LCDs with PCF8574 or MCP23008 chip based backpacks
+// WARNING:
+//	Use caution when using 3v only processors like arm and ESP8266 processors
+//	when interfacing with 5v modules as not doing proper level shifting or
+//	incorrectly hooking things up can damage the processor.
+//
+// The purpose of the sketch is to demonstrate the ability to read data from
+// the LCD.
+//
+// Sketch will print the amount of time since the Arduino has been reset
+// on the top row and then read the data from the LCD to print it on the
+// second row
+//
+// If there are errors and the arduino supports a built in LED,
+// an error status code will blink on the built in LED.
+// Error codes:
+// (1) lcd device initalization failed
+// (2) lcd device does not support reads
+// (3) error reading data from lcd device
+// (4) error writing data to lcd device
+// (5) read data mismatch
+//
+
+#include <Wire.h>
+#include <hd44780.h>
+#include <hd44780ioClass/hd44780_I2Cexp.h>
+
+hd44780_I2Cexp lcd; // declare lcd object: auto locate & config exapander chip
+
+// LCD geometry
+const int LCD_ROWS = 2;
+const int LCD_COLS = 16;
+
+void setup()
+{
+	// initialize LCD with number of columns and rows: 
+	if( lcd.begin(LCD_COLS, LCD_ROWS))
+	{
+		// begin() failed so blink the onboard LED if possible
+		fatalError(1);
+	}
+
+	// check to see if device can read by attempting to read
+	// the lcd status register. If it fails then assume it was
+	// because the lcd device does not support reads.
+	if(lcd.status() < 0)
+	{
+		lcd.print("No Read Support");
+		fatalError(2);
+	}
+}
+
+void loop()
+{
+static unsigned long lastsecs = -1; // pre-initialize with non zero value
+unsigned long secs;
+
+	secs = millis() / 1000;
+
+	// see if 1 second has passed
+	// so the display is only updated once per second
+	if(secs != lastsecs)
+	{
+		lastsecs = secs; // keep track of last seconds
+
+		// set the cursor position to top line: column 0, row 0
+		lcd.setCursor(0, 0);
+
+		// print uptime on lcd device: (time since last reset)
+		PrintUpTime(lcd, secs);
+
+		// Now copy the characters from the top line to the 2nd line
+		// This is done character by character by:
+		// - setting the character position to read
+		// - reading a character
+		// - setting the character position to write
+		// - writing the charcter read
+		for(int col = 0; col < LCD_COLS; col++)
+		{
+		int c;
+
+			lcd.setCursor(col, 0);
+			if((c = lcd.read()) < 0) // if a read error, bomb out
+				fatalError(3);
+
+			// check for ':' characters in col 2 and 5
+			// if not there, consider it a fatal read error
+			if((col == 2 || col == 5) && c != ':')
+				fatalError(5);
+
+			lcd.setCursor(col, 1);
+			if(lcd.write((uint8_t) c) != 1)
+				fatalError(4);
+		}
+	}
+}
+
+// PrintUpTime(outdev, secs) - print uptime in HH:MM:SS format
+// outdev - the device to send output
+//   secs - the total number of seconds uptime
+void PrintUpTime(Print &outdev, unsigned long secs)
+{
+unsigned int hr, mins, sec;
+
+	// convert total seconds to hours, mins, seconds
+	mins =  secs / 60;	// how many total minutes
+	hr = mins / 60;		// how many total hours
+	mins = mins % 60;	// how many minutes within the hour
+	sec = secs % 60;	// how many seconds within the minute
+		
+
+	// print uptime in HH:MM:SS format
+	// Print class does not support fixed width formatting
+	// so insert a zero if number smaller than 10
+	if(hr < 10)
+		outdev.write('0');
+	outdev.print((int)hr);
+	outdev.write(':');
+	if(mins < 10)
+		outdev.write('0');
+	outdev.print((int)mins);
+	outdev.write(':');
+	if(sec < 10)
+		outdev.write('0');
+	outdev.print((int)sec);
+}
+
+// fatalError() - loop & blink and error code
+void fatalError(int ecode)
+{
+	hd44780::fatalError(ecode); // does not return
+}
+