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