Added readme.txt for ATmega168 port.

bacnet-stack/ports/atmega168/readme.txt

@@ -0,0 +1,42 @@
+This port was done with the Atmel ATmega168 using two tools:
+1. The WinAVR compiler avr-gcc (GCC) 4.1.2 (WinAVR 20070525)
+and tools from <http://winavr.sourceforge.net/>, hints and 
+sample code from <http://www.avrfreaks.net/> and 
+<http://savannah.gnu.org/projects/avr-libc/>
+"avr-binutils, avr-gcc, and avr-libc form the heart of the 
+Free Software toolchain for the Atmel AVR microcontrollers."
+2. AVR Studio from Atmel <http://atmel.com/>
+
+The hardware is expected to utilize the signals as defined
+in the spreadsheet hardware.ods (OpenOffice.org calc).
+Attach a DS75176 RS-485 transceiver (or similar) to the USART.
+DS75176 ATmega168
+------  ---------
+ RO       RXD
+ /RE      --choice of I/O
+ DE       --choice of I/O
+ DI       TXD
+ GND      GND
+ DO       --to RS-485 wire
+ DO       --to RS-485 wire
+ +5V      From 5V Regulator
+
+The makefile allows you to build just the dlmstp or a simple
+server. dlmstp is the datalink layer for MS/TP over RS-485.
+
+I used the makefile from the command line on Windows:
+C:\code\bacnet-stack\ports\atmega168> make clean all
+
+I also used the bacnet.aps project file in AVR Studio to 
+make the project and simulate it.
+
+Note that the bacnet stack is currently layed out as encapsulating 
+modules that include both client and server functionality for each service.
+The nice thing about the all in one modules that it permits easy unit 
+testing. The bad thing is that it puts all the unused code into the build.  
+Therefore, until the code is split into separate modules, 
+the unused sections must be commented out (use #if 0, #endif).  
+
+Hopefully you find it useful!
+
+Steve Karg