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/** \mainpage AVRISP MKII Programmer Project
 *
 *  \section SSec_Compat Demo Compatibility:
 *
 *  The following list indicates what microcontrollers are compatible with this demo.
 *
 *  - Series 7 USB AVRs
 *  - Series 6 USB AVRs
 *  - Series 4 USB AVRs
 *  - Series 2 USB AVRs
 *
 *  \section SSec_Info USB Information:
 *
 *  The following table gives a rundown of the USB utilization of this demo.
 *
 * <table>
 *  <tr>
 *   <td><b>USB Mode:</b></td>
 *   <td>Device</td>
 *  </tr>
 *  <tr>
 *   <td><b>USB Class:</b></td>
 *   <td>Vendor Specific Class</td>
 *  </tr>
 *  <tr> 
 *   <td><b>USB Subclass:</b></td>
 *   <td>N/A</td>
 *  </tr>
 *  <tr>
 *   <td><b>Relevant Standards:</b></td>
 *   <td>Atmel AVRISP MKII Protocol Specification</td>
 *  </tr>
 *  <tr>
 *   <td><b>Usable Speeds:</b></td>
 *   <td>Full Speed Mode</td>
 *  </tr>
 * </table>
 *
 *  \section SSec_Description Project Description: 
 *
 *  Firmware for an AVRStudio compatible AVRISP-MKII clone programmer. This project will enable the USB AVR series of
 *  microcontrollers to act as a clone of the official Atmel AVRISP-MKII programmer, usable within AVRStudio. In its
 *  most basic form, it allows for the programming of 5V AVRs from within AVRStudio with no special hardware other than
 *  the USB AVR and the parts needed for the USB interface. If the user desires, more advanced circuits incorporating
 *  level conversion can be made to allow for the programming of 3.3V AVR designs.
 *
 *  This device spoofs Atmel's official AVRISP-MKII device PID so that it remains compatible with Atmel's AVRISP-MKII
 *  drivers. When promted, direct your OS to install Atmel's AVRISP-MKII drivers provided with AVRStudio.
 *
 *  Note that this design currently has several limitations:
 *    - Minimum ISP target clock speed of 500KHz due to hardware SPI used
 *    - No reversed/shorted target connector detection and notification
 *
 *  On AVR models with an ADC converter, AVCC should be tied to 5V (e.g. VBUS) and the VTARGET_ADC_CHANNEL token should be
 *  set to an appropriate ADC channel number in the project makefile for VTARGET detection to operate correctly. On models
 *  without an ADC converter, VTARGET will report at a fixed 5V level.
 *
 *  When compiled for the XPLAIN board target, this will automatically configure itself for the correct connections to the
 *  XPLAIN's XMEGA AVR, and will enable only PDI programming support.
 *
 *
 *  Connections to the device for SPI programming (when enabled):
 *
 *  <table>
 *   <tr>
 *    <td><b>Programmer Pin:</b></td>
 *    <td><b>Target Device Pin:</b></td>
 *    <td><b>ISP 6 Pin Layout:</b></td>
 *   </tr>
 *   <tr>
 *    <td>MISO</td>
 *    <td>PDO</td>
 *    <td>1</td>
 *   </tr>
 *   <tr>
 *    <td>ADCx <b><sup>1</sup></b></td>
 *    <td>VTARGET</td>
 *    <td>2</td>
 *   </tr>
 *   <tr>
 *    <td>SCLK</td>
 *    <td>SCLK</td>
 *    <td>3</td>
 *   </tr>
 *   <tr>
 *    <td>MOSI</td>
 *    <td>PDI</td>
 *    <td>4</td>
 *   </tr>
 *   <tr>
 *    <td>PORTx.y <b><sup>2</sup></b></td>
 *    <td>/RESET</td>
 *    <td>5</td>
 *   </tr>
 *   <tr>
 *    <td>GND</td>
 *    <td>GND</td>
 *    <td>6</td>
 *   </tr>
 *  </table>
 *
 *  <b><sup>1</sup></b> <i>Optional, see \ref SSec_Options section - for USB AVRs with ADC modules only</i> \n
 *  <b><sup>2</sup></b> <i>See \ref SSec_Options section</i>
 *
 *
 *  Connections to the device for PDI programming (when enabled):
 *
 *  <table>
 *   <tr>
 *    <td><b>Programmer Pin:</b></td>
 *    <td><b>Target Device Pin:</b></td>
 *    <td><b>PDI 6 Pin Layout:</b></td>
 *   </tr>
 *   <tr>
 *    <td>MISO</td>
 *    <td>DATA</td>
 *    <td>1</td>
 *   </tr>
 *   <tr>
 *    <td>ADCx <b><sup>1</sup></b></td>
 *    <td>VTARGET</td>
 *    <td>2</td>
 *   </tr>
 *   <tr>
 *    <td>N/A</td>
 *    <td>N/A</td>
 *    <td>3</td>
 *   </tr>
 *   <tr>
 *    <td>N/A</td>
 *    <td>N/A</td>
 *    <td>4</td>
 *   </tr>
 *   <tr>
 *    <td>PORTx.y <b><sup>2</sup></b></td>
 *    <td>CLOCK</td>
 *    <td>5</td>
 *   </tr>
 *   <tr>
 *    <td>GND</td>
 *    <td>GND</td>
 *    <td>6</td>
 *   </tr>
 *  </table>
 *
 *  \section SSec_Options Project Options
 *
 *  The following defines can be found in this demo, which can control the demo behaviour when defined, or changed in value.
 *
 *  <table>
 *   <tr>
 *    <td><b>Define Name:</b></td>
 *    <td><b>Location:</b></td>
 *    <td><b>Description:</b></td>
 *   </tr>
 *   <tr>
 *    <td>RESET_LINE_PORT</td>
 *    <td>Makefile CDEFS</td>
 *    <td>PORT register for the programmer's target RESET line. <i>Ignored when compiled for the XPLAIN board.</i></td>
 *   </tr>
 *   <tr>
 *    <td>RESET_LINE_DDR</td>
 *    <td>Makefile CDEFS</td>
 *    <td>DDR register for the programmer's target RESET line. <i>Ignored when compiled for the XPLAIN board.</i></td>
 *   </tr>
 *   <tr>
 *    <td>RESET_LINE_MASK</td>
 *    <td>Makefile CDEFS</td>
 *    <td>Mask for the programmer's target RESET line on the chosen port. <b>Must not be the AVR's /SS pin</b>, as the
 *        target pins are tri-stated when not in use, and low signals on the /SS pin will force SPI slave mode when the
 *        pin is configured as an input. When in PDI programming mode, this is the target clock pin.
 *        <i>Ignored when compiled for the XPLAIN board.</i></td>
 *   </tr>
 *   <tr>
 *    <td>VTARGET_ADC_CHANNEL</td>
 *    <td>Makefile CDEFS</td>
 *    <td>ADC channel number (on supported AVRs) to use for VTARGET level detection.</td> 
 *   </tr>
 *   <tr>
 *    <td>ENABLE_ISP_PROTOCOL</td>
 *    <td>Makefile CDEFS</td>
 *    <td>Define to enable SPI programming protocol support. <i>Ignored when compiled for the XPLAIN board.</i></td>  
 *   </tr>
 *   <tr>
 *    <td>ENABLE_PDI_PROTOCOL</td>
 *    <td>Makefile CDEFS</td>
 *    <td>Define to enable XMEGA PDI programming protocol support. <i>Ignored when compiled for the XPLAIN board.</i></td>  
 *   </tr>
 *  </table>
 */