Add serial support

aux/build.sh

@@ -3,8 +3,15 @@
 LEGO=$HOME/src/lego/lms2012
 P="`pwd`"
 F="$P"/pxt
-set -xe
+set -e
 cd $LEGO/lmssrc/adk/lmsasm
+echo "Compiling..."
 java -jar assembler.jar $F
 cd "$P"
-node -p 'require("fs").readFileSync("pxt.rbf").toString("hex").replace(/5858585858(58)+/, "XX")'
+echo "Hex to paste:"
+echo
+echo "const rbfTemplate = \`"
+node -p 'require("fs").readFileSync("pxt.rbf").toString("hex").replace(/5858585858(58)+/, "XX").replace(/.{1,80}/g, f => f + "\n").trim()'
+echo "\`"
+echo
+rm -f pxt.rbf

aux/pxt.lms

@@ -4,12 +4,15 @@ vmthread  MAIN
   DATA8   State
   DATA32  Status
   //DATA32  Timer
+  DATA16 Serial
 
   UI_WRITE(LED,LED_RED)
   UI_DRAW(TEXT,FG_COLOR,48,62,'Starting...')
   UI_DRAW(UPDATE)
+  // Make sure VM knows that /tmp/serial.txt is open for writing and can stream the content
+  FILE(OPEN_WRITE, '/tmp/serial.txt', Serial)
+  // Actual filename is patched-in here
   SYSTEM('XXXXXXXXX', Status)
-  //SYSTEM('../prjs/BrkProg_SAVE/binary.elf', Status)
 Loop:
   UI_BUTTON(WAIT_FOR_PRESS)
   UI_BUTTON(SHORTPRESS,BACK_BUTTON,State)