diff --git a/AVRsack/ASBuilder.swift b/AVRsack/ASBuilder.swift
index a9aef6d..e114ce2 100644
--- a/AVRsack/ASBuilder.swift
+++ b/AVRsack/ASBuilder.swift
@@ -21,15 +21,40 @@ class ASBuilder {
         task!.currentDirectoryPath  = dir.path!
         task!.launchPath            = NSBundle.mainBundle().pathForResource("BuildProject", ofType: "")!
         
+        let fileManager         = NSFileManager.defaultManager()
         let libPath     = (ASLibraries.instance().directories as NSArray).componentsJoinedByString(":")
         var args        = [NSString]()
         let boardProp   = ASHardware.instance().boards[board]!
+        var corePath    = ""
+        var variantPath : NSString?
+        for hw in ASHardware.instance().directories {
+            corePath = hw+"/cores/"+boardProp["build.core"]
+            if fileManager.fileExistsAtPath(corePath) {
+                if boardProp["build.variant"] != "" {
+                    variantPath = hw+"/variants/"+boardProp["build.variant"]
+                    if !fileManager.fileExistsAtPath(corePath) {
+                        variantPath = nil
+                    }
+                }
+                break
+            } else {
+                corePath = ""
+            }
+        }
+        if corePath == "" {
+            NSLog("Unable to find core %s\n", boardProp["build.core"])
+            return
+        }
         args.append("board="+board)
         args.append("mcu="+boardProp["build.mcu"])
         args.append("f_cpu="+boardProp["build.f_cpu"])
         args.append("core="+boardProp["build.core"])
         args.append("variant="+boardProp["build.variant"])
         args.append("libs="+libPath)
+        args.append("core_path="+corePath)
+        if variantPath != nil {
+            args.append("variant_path="+variantPath!)
+        }
         args.append("--")
         args            += files.paths
         task!.arguments =   args;
diff --git a/AVRsack/BuildProject b/AVRsack/BuildProject
index 03d61d2..830361e 100755
--- a/AVRsack/BuildProject
+++ b/AVRsack/BuildProject
@@ -9,6 +9,7 @@
 #
 
 require 'fileutils.rb'
+require 'rake'
 
 BUILD = {
     'board'   => 'uno',
@@ -33,9 +34,31 @@ def createBuildDirectory
     FileUtils::mkdir_p "#{$SKETCH_DIR}", :verbose => true
 end
 
+HEADERMAP  = {}
+def buildHeaderMap
+    paths       = Rake::FileList.new(BUILD['libs'].split(':').reverse)
+    paths.each do |path|
+        libs        = Rake::FileList.new(path+"/*")
+        libs.each do |lib|
+            headers = Rake::FileList.new(lib+"/**/*.h")
+            headers.each do |h|
+                name    = h[lib.length+1..-1]
+                next if name =~ %r|^utility/|
+                if !HEADERMAP[name] or HEADERMAP[name].pathmap('%f') != name.pathmap('%X')
+                    HEADERMAP[name] = lib
+                end
+            end
+        end
+    end
+    p HEADERMAP
+end
+
 def parseInoFiles
-    $LIBPATH   = BUILD['libs'].split(':').reverse
     $LIBRARIES = []
+    $CORES     = [BUILD['core_path']]
+    if BUILD['variant_path']
+        $CORES << BUILD['variant_path']
+    end
     ARGV.each_index do |arg|
         if ARGV[arg] =~ /\.ino$/
             outName     = "#{$SKETCH_DIR}/"+File.basename(ARGV[arg], '.ino')+".cpp"
@@ -81,25 +104,41 @@ def smashSpaces(s)
 end
                                  
 def addLibrary(header)
-    $LIBPATH.each do |path|
-        Dir.glob("#{path}/*").each do |lib|
-            if File.exists?("#{lib}/#{header}")
-                $LIBRARIES << lib
-            end
-        end
+    lib = HEADERMAP[header]
+    if lib && !$LIBRARIES.include?(lib)
+        $LIBRARIES << lib
     end
 end
 
 parseArguments
 createBuildDirectory
+buildHeaderMap
 parseInoFiles
 
 File.open("#{$BUILD_DIR}/Rakefile", 'w') do |rakeFile|
+    SOURCES = FileList.new(ARGV).select {|f| f =~ /\.(c|cpp|cp|cxx|S)$/}
+    INCLUDES= ($CORES+$LIBRARIES).map {|l| " +\n   \" -I'#{l}'\""}.join('')
     rakeFile.print <<END_RAKE
-LIBRARIES=#{$LIBRARIES.join(':')}
-FILES    = [
-    #{ARGV.join('\n')}
-]
+CC          = '/usr/local/CrossPack-AVR/bin/avr-g++ -c -g -Os -Wall -fno-exceptions -ffunction-sections -fdata-sections -mmcu=#{BUILD['mcu']} -DF_CPU=#{BUILD['f_cpu']} -MMD -DUSB_VID=null -DUSB_PID=null -DARDUINO=105 -I ../..'#{INCLUDES}
+AR          = '/usr/local/CrossPack-AVR/bin/avr-ar crsv'
+LIBRARIES   = [#{$LIBRARIES.map{|l| "'"+l+"'"}.join(' ')}]
+
+def compile(dest, *src)
+    directory dest
+    archive = dest.ext('.a')
+    sources = Rake::FileList.new(src)
+    objects = sources.pathmap(dest+"/%n.o")
+    objects.each_index do |i|
+        file objects[i] => sources[i] do
+            sh "%s '%s' -o '%s'" % [CC, sources[i], objects[i]]
+        end
+    end
+    file archive => objects do
+        sh ("%s '%s' " % [AR, archive])+objects.map {|o| "'"+o+"'"}.join(" ")
+    end
+end
+
+compile('sketch', #{SOURCES.map{|f| "'../../"+f+"'"}.join(', ')})
 END_RAKE
 
 end