/* *********************************************************************
 * pitone.cpp  repeater PL Tone sine wave generator
 * 
 * Copyright 2016-2017 by Larry Gauthier, K8UT
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * ---------------------------------------------------------------------
 * Requires C++ 2014 edition in compile statement
 *	TO COMPILE:  g++ -Wall -std=c++14 -o "%e" "%f" -l wiringPi
 *	TO EXECUTE:  sudo ./pitone <arguments - see splash screen>
 * *********************************************************************
	Derived from Raspberry Pi I2C interface demo by Byron Jacquot @ SparkFun Electronics>
	4/2/2014  https://github.com/sparkfun/Pi_Wedge
	
	PREPARE YOUR PI FOR I2C OPERATION:
	 
	Ensure you have the latest rev of everything. From the CLI:
	* sudo apt-get update
	* sudo apt-get upgrade
	* sudo rpi-update
	
	Turn on the I2C interface:
	* Pi >Preferencews >Rasperry Pi Configuration >Interfaces: enable I2C
	
	Increase I2C baudrate to 1200000:
	* From the CLI: sudo nano /boot/config.txt
	* Near the bottom of the file, find the entry for I2C. Should read "dtparam=i2c_arm=on" Add the following in a line immediately before that line "dtparam=i2c_baudrate=1200000"
	* Save the file and reboot
	* 
	Get some tools for I2C operation:
	* From the CLI: sudo apt-get install -y i2c-tools
	
	Examine the I2C settings:
	* FILE DESCRIPTOR? From the CLI: i2cdetect -y 1
	** default descriptor is 60. Mine showed up as 62. (?)
	* BAUDRATE? From the CLI: dmesg | grep i2c
	
	Copy the Pi Tone program to your Pi
	* Probably easiest to transfer using WinSCP
	* Set excutable attributes from WinSCP, OR
	* Make executable from the CLI with: sudo chmod +x pitone
	
	Run the program with:
	* ./pitone
	* Watch the MCP4725 output with a scope or voltmeter
	* Stop with ctrl+C
	
	Auto-start and Improve stability of the timing using the linix CHRT commane
	* in the /etc/rc.local startup file: sudo nano /etc/rc.local
	* add the line: chrt - -99 ./pitone 110.9 32
	
	The I2C API is documented here:
	https://projects.drogon.net/raspberry-pi/wiringpi/i2c-library/
	
	The init call returns a standard file descriptor.  More detailed configuration
	of the interface can be performed using ioctl calls on that descriptor.
	See the wiringPi I2C implementation (wiringPi/wiringPiI2C.c) for some examples.
	Parameters configurable with ioctl are documented here:
	http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/i2c/dev-interface
******************************************************************************/