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

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+// vi:ts=4
+// ----------------------------------------------------------------------------
+// UpTime - simple demonstration of lcd
+// Created by Bill Perry 2017-05-11
+// 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.
+// 
+// Sketch will print "UpTime" on top row of lcd
+// and will print the amount of time since the Arduino has been reset
+// on the second row.
+//
+// If initialization of the LCD fails and the arduino supports a built in LED,
+// the sketch will simply blink the built in LED.
+//
+// NOTE:
+//	If the sketch fails to produce the expected results, or blinks the LED,
+//	run the included I2CexpDiag sketch to test the i2c signals and the LCD.
+
+#include <Wire.h>
+#include <hd44780.h>                       // main hd44780 header
+#include <hd44780ioClass/hd44780_I2Cexp.h> // i2c expander i/o class header
+
+hd44780_I2Cexp lcd; // declare lcd object: auto locate & config exapander chip
+
+// LCD geometry
+const int LCD_COLS = 16;
+const int LCD_ROWS = 2;
+
+void setup()
+{
+int status;
+
+	// initialize LCD with number of columns and rows: 
+	// hd44780 returns a status from begin() that can be used
+	// to determine if initalization failed.
+	// the actual status codes are defined in <hd44780.h>
+	// See the values RV_XXXX
+	//
+	// looking at the return status from begin() is optional
+	// it is being done here to provide feedback should there be an issue
+	//
+	// note:
+	//	begin() will automatically turn on the backlight
+	//
+
+	status = lcd.begin(LCD_COLS, LCD_ROWS);
+	if(status) // non zero status means it was unsuccesful
+	{
+		// hd44780 has a fatalError() routine that blinks an led if possible
+		// begin() failed so call fatalError() with the error code.
+		hd44780::fatalError(status); // does not return
+	}
+	// initalization was successful, the backlight should be on now
+
+	// Print a message to the LCD
+	lcd.print(" UpTime");
+
+	if(LCD_ROWS < 2)
+		delay(3000);
+}
+
+void loop()
+{
+static unsigned long lastsecs = -1; // pre-initialize with non zero value
+unsigned long secs;
+int status;
+
+	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 column 0, row 1
+		// note: row 1 is the second row from top,
+		// since row counting begins with 0
+		// if display has only 1 line, it will appear on that line
+		status = lcd.setCursor(0, 1);
+		if(status) // non zero status means it was unsuccesful
+		{
+			// setCursor() failed so call fatalError() with the error code.
+			hd44780::fatalError(status); // does not return
+		}
+
+		// print uptime on lcd device: (time since last reset)
+		PrintUpTime(lcd, secs);
+	}
+}
+
+// PrintUpTime(outdev, secs) - print uptime in HH:MM:SS format
+// outdev - the device to send output
+//   secs - the total number of seconds uptime
+//
+// This is a fancy output routine.
+// outdev is a Print class object which indicates
+// where the output should be sent.
+// PrintUpTime can be used with any object that uses the Print class.
+// This code works with Serial objects, as well as the the hd44780 lcd objects.
+// i.e. you can call with Serial: PrintUpTime(Serial, seconds);
+
+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
+
+	if(hr > 99)
+		hr %= 100; // limit hr to 0-99
+
+	// 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);
+}