Updated readme file for Atmel AVR ATmega168 port.

bacnet-stack/ports/atmega168/readme.txt

@@ -2,11 +2,13 @@ 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/>
+<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/>
 
+Alternatively, the project also builds using IAR Embedded Workbench AVR.
+
 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.
@@ -27,8 +29,17 @@ 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
 
+CStack check for GCC is included in the device object as property 512.  
+The compile shows 648 bytes of RAM used, and the ATmega168 has 1024 bytes
+of RAM, leaving 376 for the CStack.  Property 512 index 0 returns 376 from
+a ReadProperty request.  My understanding is that the remaining unallocated
+RAM is used for the CStack.  Keep this in mind when developing.  
+After some ReadProperty and WriteProperty requests, the CStack shows 
+159 CStack bytes free, meaning that 216 bytes of CStack are used.  
+Note that the value 0xC5 (197) was used to paint the CStack. 
+
 I also used the bacnet.aps project file in AVR Studio to 
-make the project and simulate it.
+make the project and simulate it, but have not kept it updated (FIXME).
 
 Compiler settings for IAR Embedded Workbench (FIXME: makefile?):
 General Options
@@ -48,8 +59,8 @@ Library Options
 Heap Configuration
  CLIB heap size: 0x10
 System
- CSTACK: 0x20 (0x60?)
+ CSTACK: 0x200
- RSTACK: 16 (32?)
+ RSTACK: 32
  Initialize unused interrupt vectors with RETI instructions (enabled)
  Enable bit defnitions in I/O-Include files. (enabled)
 MISRA C
@@ -90,10 +101,15 @@ Preprocessor
  Preinclude file: (none)
  Defined symbols: 
   BACDL_MSTP
-  MAX_APDU=128
+  MAX_APDU=50
   BIG_ENDIAN=0
   MAX_TSM_TRANSACTIONS=0
   BACAPP_REAL
+  BACAPP_UNSIGNED
+  BACAPP_ENUMERATED
+  BACAPP_CHARACTER_STRING
+  BACAPP_OBJECT_ID
+  WRITE_PROPERTY
 Diagnostics 
  (not enabled)
 MISRA C
@@ -114,6 +130,16 @@ disabled in the project file.
   be unsigned (in functions such as strncpy(), etc.). It may 
   be possible to recompile the libraries with signed plain char's.
 
+The BACnet Capabilities include WhoIs, I-Am, ReadProperty, and 
+WriteProperty support.  The BACnet objects include a Device object,
+10 Binary Value objects, and 10 Analog Value objects.  An LED is 
+controlled by Binary Value object instance 0.  All required object
+properties can be retrieved using ReadProperty.  The Present_Value
+property of the Analog Value and Binary Value objects can be 
+written using WriteProperty.  The Object_Identifier, Object_Name, 
+Max_Info_Frames, Max_Master, and baud rate (property 9600) of the 
+Device object can be written using WriteProperty.
+
 Hopefully you find this code useful!
 
 Steve Karg <skarg@users.sourceforge.net>