CVS: python/msp430 jtag.py,1.11,1.12

Update of /cvsroot/mspgcc/python/msp430
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv4068/msp430

Modified Files:
	jtag.py 
Log Message:
add some docs, better error messages


Index: jtag.py
===================================================================
RCS file: /cvsroot/mspgcc/python/msp430/jtag.py,v
retrieving revision 1.11
retrieving revision 1.12
diff -u -w -d -r1.11 -r1.12
--- jtag.py	5 Oct 2005 15:25:23 -0000	1.11
+++ jtag.py	13 Oct 2005 01:02:37 -0000	1.12
@@ -41,10 +41,19 @@
     try:
         import _parjtag
     except ImportError:
-        raise ImportError("Can not find neither _parjtag nor ctypes. No JTAG backend available.")
+        raise ImportError(
+            "Can not find neither _parjtag nor ctypes. No JTAG backend available.\n"
+            "\n"
+            "The ctypes backend is prefered. Make sure that the ctypes python\n"
+            "extension is available on this system.\n"
+            "\n"
+            "Alternatively, the older _parjtag backend is a python extension that\n"
+            "can be built from sources from http://mspgcc.sf.net\n"
+        )
     else:
         backend = "_parjtag so/dll"
 else:
+    #create a wrapper class with ctypes, that has the same API as _parjtag
     backend = "ctypes"
     
     STATUS_OK   = 0
@@ -53,10 +62,16 @@
     WRITE       = 0
     READ        = 1
     if sys.platform == 'win32':
+        #the library uis found on the PATH, respectively in the executables directory
         MSP430mspgcc = ctypes.windll.MSP430mspgcc
     else:
+        #an absolute path to the library has to be given.
+        #LIBMSPGCC_PATH is used to pass its location
         import os
+        try:
         MSP430mspgcc = ctypes.cdll.LoadLibrary(os.path.join(os.environ['LIBMSPGCC_PATH'], 'libMSP430mspgcc.so'))
+        except KeyError:
+            raise KeyError('The environment variable "LIBMSPGCC_PATH" must point to the folder that contains "libMSP430mspgcc.so"')
     
     MSP430_Initialize               = MSP430mspgcc.MSP430_Initialize
     MSP430_Initialize.argtypes      = [ctypes.c_char_p, ctypes.POINTER(ctypes.c_long)]



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