diff --git a/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java b/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
index e69d671d2e4..0ec94535846 100644
--- a/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
+++ b/arduino-core/src/cc/arduino/contributions/packages/ContributionsIndexer.java
@@ -80,7 +80,7 @@ public ContributionsIndexer(File preferencesFolder, Platform platform, Signature
 
   public void parseIndex() throws Exception {
     File defaultIndexFile = getIndexFile(Constants.DEFAULT_INDEX_FILE_NAME);
-    if (!signatureVerifier.isSigned(defaultIndexFile)) {
+    if (!PreferencesData.getBoolean("allow_insecure_packages") && !signatureVerifier.isSigned(defaultIndexFile)) {
       throw new SignatureVerificationFailedException(Constants.DEFAULT_INDEX_FILE_NAME);
     }
     index = parseIndex(defaultIndexFile);
diff --git a/build/arduino-builder-arm-1.3.15.tar.bz2.sha b/build/arduino-builder-arm-1.3.15.tar.bz2.sha
new file mode 100644
index 00000000000..02c29b4a26c
--- /dev/null
+++ b/build/arduino-builder-arm-1.3.15.tar.bz2.sha
@@ -0,0 +1 @@
+e83845803bbaad5c4489e0c4d3cdf84d93637a5d
diff --git a/build/build.xml b/build/build.xml
index 444c6502bff..d88c233d9c9 100644
--- a/build/build.xml
+++ b/build/build.xml
@@ -26,6 +26,7 @@
   <condition property="platform" value="windows"><os family="windows" /></condition>
   <condition property="platform" value="linux32"><os family="unix" arch="i386" /></condition>
   <condition property="platform" value="linux64"><os family="unix" arch="amd64" /></condition>
+  <condition property="platform" value="linuxarm"><os family="unix" arch="arm" /></condition>
 
   <condition property="macosx"><equals arg1="${platform}" arg2="macosx" /></condition>
   <condition property="windows"><equals arg1="${platform}" arg2="windows" /></condition>
@@ -33,20 +34,26 @@
   <condition property="linux64"><equals arg1="${platform}" arg2="linux64" /></condition>
   <condition property="linux"><equals arg1="${platform}" arg2="linux32" /></condition>
   <condition property="linux"><equals arg1="${platform}" arg2="linux64" /></condition>
+  <condition property="linux"><equals arg1="${platform}" arg2="linuxarm" /></condition>
 
   <condition property="staging_folder" value="macosx"><equals arg1="${platform}" arg2="macosx" /></condition>
   <condition property="staging_folder" value="windows"><equals arg1="${platform}" arg2="windows" /></condition>
   <condition property="staging_folder" value="linux"><equals arg1="${platform}" arg2="linux32" /></condition>
   <condition property="staging_folder" value="linux"><equals arg1="${platform}" arg2="linux64" /></condition>
+  <condition property="staging_folder" value="linux"><equals arg1="${platform}" arg2="linuxarm" /></condition>
 
   <condition property="staging_hardware_folder" value="Arduino.app/Contents/Java/hardware"><equals arg1="${platform}" arg2="macosx" /></condition>
   <condition property="staging_hardware_folder" value="hardware"><equals arg1="${platform}" arg2="windows" /></condition>
   <condition property="staging_hardware_folder" value="hardware"><equals arg1="${platform}" arg2="linux32" /></condition>
   <condition property="staging_hardware_folder" value="hardware"><equals arg1="${platform}" arg2="linux64" /></condition>
+  <condition property="staging_hardware_folder" value="hardware"><equals arg1="${platform}" arg2="linuxarm" /></condition>
 
   <condition property="arch-bits" value="32">
     <equals arg1="${platform}" arg2="linux32"/>
   </condition>
+  <condition property="arch-bits" value="32">
+    <equals arg1="${platform}" arg2="linuxarm"/>
+  </condition>
   <condition property="arch-bits" value="64">
     <equals arg1="${platform}" arg2="linux64"/>
   </condition>
@@ -58,10 +65,12 @@
   <property name="WINDOWS_BUNDLED_JVM" value="${java.home}"/>
   <property name="LINUX32_BUNDLED_JVM" value="none"/>
   <property name="LINUX64_BUNDLED_JVM" value="none"/>
+  <property name="LINUXARM_BUNDLED_JVM" value="none"/>
   <condition property="linux-bundle-jvm-task" value="noop">
     <and>
       <equals arg1="${LINUX32_BUNDLED_JVM}" arg2="none"/>
       <equals arg1="${LINUX64_BUNDLED_JVM}" arg2="none"/>
+      <equals arg1="${LINUXARM_BUNDLED_JVM}" arg2="none"/>
     </and>
   </condition>
   <condition property="linux-bundle-jvm-task" value="bundle">
@@ -72,6 +81,9 @@
       <not>
         <equals arg1="${LINUX64_BUNDLED_JVM}" arg2="none"/>
       </not>
+      <not>
+        <equals arg1="${LINUXARM_BUNDLED_JVM}" arg2="none"/>
+      </not>
     </or>
   </condition>
 
@@ -426,8 +438,8 @@
     </antcall>
 
     <antcall target="unzip">
-      <param name="archive_file" value="./libastylej-2.05.1.zip" />
-      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1.zip" />
+      <param name="archive_file" value="./libastylej-2.05.1-3.zip" />
+      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1-3.zip" />
       <param name="final_folder" value="${staging_folder}/libastylej-2.05.1" />
       <param name="dest_folder" value="${staging_folder}" />
     </antcall>
@@ -625,10 +637,12 @@
         <fileset dir="linux/work" includes="arduino" />
         <fileset dir="linux/work" includes="**/*.sh" />
     </chmod>
+  </target>
 
+  <target name="linux-libastyle-x86" depends="linux-build" description="Download libastyle.so for x86/x64 arch">
     <antcall target="unzip">
-      <param name="archive_file" value="./libastylej-2.05.1.zip" />
-      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1.zip" />
+      <param name="archive_file" value="./libastylej-2.05.1-3.zip" />
+      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1-3.zip" />
       <param name="final_folder" value="${staging_folder}/libastylej-2.05.1" />
       <param name="dest_folder" value="${staging_folder}" />
     </antcall>
@@ -650,7 +664,64 @@
 
   </target>
 
-  <target name="linux32-build" depends="linux-build" description="Build linux (32-bit) version">
+  <target name="linux-libastyle-arm" depends="linux-build" description="Download libastyle.so for ARM">
+    <antcall target="unzip">
+      <param name="archive_file" value="./libastylej-2.05.1-3.zip" />
+      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1-3.zip" />
+      <param name="final_folder" value="${staging_folder}/libastylej-2.05.1" />
+      <param name="dest_folder" value="${staging_folder}" />
+    </antcall>
+    <copy file="linux/libastylej-2.05.1/libastylej_arm.so" tofile="linux/work/lib/libastylej.so" />
+    <chmod perm="755" file="linux/work/lib/libastylej.so" />
+
+    <antcall target="portable-${portable}">
+      <param name="parentdir" value="linux/work" />
+    </antcall>
+
+    <antcall target="unzip">
+      <param name="archive_file" value="./liblistSerials-${LIBLISTSERIAL-VERSION}.zip" />
+      <param name="archive_url" value="http://downloads.arduino.cc/liblistSerials/liblistSerials-${LIBLISTSERIAL-VERSION}.zip" />
+      <param name="final_folder" value="${staging_folder}/liblistSerials-${LIBLISTSERIAL-VERSION}" />
+      <param name="dest_folder" value="${staging_folder}" />
+    </antcall>
+    <copy file="linux/liblistSerials-${LIBLISTSERIAL-VERSION}/arm/liblistSerialsj.so" todir="linux/work/lib/" />
+    <chmod perm="755" file="linux/work/lib/liblistSerialsj.so" />
+
+  </target>
+
+  <target name="linuxarm-build" depends="linux-libastyle-arm" description="Build linux (32-bit) version">
+    <antcall target="linux-jvm-${linux-bundle-jvm-task}">
+      <param name="JVM" value="${LINUXARM_BUNDLED_JVM}"/>
+    </antcall>
+
+    <delete dir="${staging_folder}/arduino-builder-arm" includeemptydirs="true"/>
+    <mkdir dir="${staging_folder}/arduino-builder-arm"/>
+    <antcall target="untar">
+      <param name="archive_file" value="./arduino-builder-arm-${ARDUINO-BUILDER-VERSION}.tar.bz2" />
+      <param name="archive_url" value="http://downloads.arduino.cc/tools/arduino-builder-arm-${ARDUINO-BUILDER-VERSION}.tar.bz2" />
+      <param name="final_folder" value="${staging_folder}/arduino-builder-arm/arduino-builder" />
+      <param name="dest_folder" value="${staging_folder}/arduino-builder-arm" />
+    </antcall>
+    <copy file="${staging_folder}/arduino-builder-arm/arduino-builder" tofile="linux/work/arduino-builder" />
+    <chmod perm="755" file="linux/work/arduino-builder" />
+    <move file="${staging_folder}/arduino-builder-arm/tools" tofile="linux/work/tools-builder"/>
+    <copy todir="linux/work/hardware" overwrite="true">
+      <fileset dir="${staging_folder}/arduino-builder-arm/hardware" includes="*.txt"/>
+    </copy>
+    <delete dir="${staging_folder}/arduino-builder-arm" includeemptydirs="true"/>
+
+    <antcall target="avr-toolchain-bundle">
+      <param name="unpack_target" value="untar"/>
+      <param name="gcc_archive_file" value="avr-gcc-4.8.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2"/>
+      <param name="gcc_version" value="4.8.1-arduino5"/>
+      <param name="avrdude_archive_file" value="avrdude-6.0.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2"/>
+      <param name="avrdude_version" value="6.0.1-arduino5"/>
+    </antcall>
+
+    <antcall target="package-library-index-json-bundle"/>
+  </target>
+
+  <target name="linux32-build" depends="linux-libastyle-x86" description="Build linux (32-bit) version">
     <antcall target="linux-jvm-${linux-bundle-jvm-task}">
       <param name="JVM" value="${LINUX32_BUNDLED_JVM}"/>
     </antcall>
@@ -682,7 +753,7 @@
     <antcall target="package-library-index-json-bundle"/>
   </target>
 
-  <target name="linux64-build" depends="linux-build" description="Build linux (64-bit) version">
+  <target name="linux64-build" depends="linux-libastyle-x86" description="Build linux (64-bit) version">
     <antcall target="linux-jvm-${linux-bundle-jvm-task}">
       <param name="JVM" value="${LINUX64_BUNDLED_JVM}"/>
     </antcall>
@@ -730,6 +801,8 @@
 
   <target name="linux64-run" depends="build,start"/>
 
+  <target name="linuxarm-run" depends="build,start"/>
+
   <target name="linux32-start">
     <exec executable="./linux/work/arduino" spawn="false" failonerror="true"/>
   </target>
@@ -738,6 +811,10 @@
     <exec executable="./linux/work/arduino" spawn="false" failonerror="true"/>
   </target>
 
+  <target name="linuxarm-start">
+    <exec executable="./linux/work/arduino" spawn="false" failonerror="true"/>
+  </target>
+
   <!-- Set '${dist_file}_available' property if toolchain dist_file is downloaded              -->
   <!-- Set '${dist_file}_installed' property if toolchain is installed in working directory    -->
   <!--                              hardware/tools/${dist_check_file} is checked for existence -->
@@ -817,10 +894,13 @@
   </target>
 
   <target name="linux32-dist" depends="linux-dist"
-	  description="Build .tar.xz of linux version" />
+	  description="Build .tar.xz of linux x86_32 version" />
 
   <target name="linux64-dist" depends="linux-dist"
-	  description="Build .tar.xz of linux version" />
+	  description="Build .tar.xz of linux x86_64 version" />
+
+  <target name="linuxarm-dist" depends="linux-dist"
+	  description="Build .tar.xz of linux armhf version" />
 
   <!-- - - - - - - - -->
   <!-- Windows       -->
@@ -899,8 +979,8 @@
     <antcall target="windows-build-avr-toolchain" />
 
     <antcall target="unzip">
-      <param name="archive_file" value="./libastylej-2.05.1.zip" />
-      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1.zip" />
+      <param name="archive_file" value="./libastylej-2.05.1-3.zip" />
+      <param name="archive_url" value="http://downloads.arduino.cc/libastylej-2.05.1-3.zip" />
       <param name="final_folder" value="${staging_folder}/libastylej-2.05.1" />
       <param name="dest_folder" value="${staging_folder}" />
     </antcall>
diff --git a/build/build_all_dist.bash b/build/build_all_dist.bash
index 0e98b827cb2..4d1c60e3577 100755
--- a/build/build_all_dist.bash
+++ b/build/build_all_dist.bash
@@ -12,6 +12,9 @@ mv linux/arduino-*-linux32.tar.xz ../
 ant -Djava.net.preferIPv4Stack=true -Dplatform=linux64 $@ clean dist
 mv linux/arduino-*-linux64.tar.xz ../
 
+ant -Djava.net.preferIPv4Stack=true -Dplatform=linuxarm $@ clean dist
+mv linux/arduino-*-linuxarm.tar.xz ../
+
 ant -Djava.net.preferIPv4Stack=true -Dplatform=windows $@ clean dist
 mv windows/arduino-*-windows.zip ../
 
diff --git a/build/build_pull_request.bash b/build/build_pull_request.bash
index 2ca6a709282..5fc7a452265 100755
--- a/build/build_pull_request.bash
+++ b/build/build_pull_request.bash
@@ -18,5 +18,5 @@ fi
 
 VERSION="PR-${ghprbPullId}-BUILD-${BUILD_NUMBER}"
 
-./build_all_dist.bash -Dversion="${VERSION}" -DMACOSX_BUNDLED_JVM=$MACOSX_BUNDLED_JVM -DWINDOWS_BUNDLED_JVM=$WINDOWS_BUNDLED_JVM -DLINUX32_BUNDLED_JVM=$LINUX32_BUNDLED_JVM -DLINUX64_BUNDLED_JVM=$LINUX64_BUNDLED_JVM
+./build_all_dist.bash -Dversion="${VERSION}" -DMACOSX_BUNDLED_JVM=$MACOSX_BUNDLED_JVM -DWINDOWS_BUNDLED_JVM=$WINDOWS_BUNDLED_JVM -DLINUX32_BUNDLED_JVM=$LINUX32_BUNDLED_JVM -DLINUX64_BUNDLED_JVM=$LINUX64_BUNDLED_JVM -DLINUXARM_BUNDLED_JVM=$LINUXARM_BUNDLED_JVM
 
diff --git a/build/libastylej-2.05.1-3.zip.sha b/build/libastylej-2.05.1-3.zip.sha
new file mode 100644
index 00000000000..36e6e9d482c
--- /dev/null
+++ b/build/libastylej-2.05.1-3.zip.sha
@@ -0,0 +1 @@
+948f14cd445429e252d2a9cd3451c79e0d9c468a
diff --git a/build/libastylej-2.05.1.zip.sha b/build/libastylej-2.05.1.zip.sha
deleted file mode 100644
index 919065add56..00000000000
--- a/build/libastylej-2.05.1.zip.sha
+++ /dev/null
@@ -1 +0,0 @@
-0b5e1be1985eed35657f60869a6cad916bd066fc
diff --git a/build/linux/avr-gcc-4.8.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha b/build/linux/avr-gcc-4.8.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha
new file mode 100644
index 00000000000..62a78b76735
--- /dev/null
+++ b/build/linux/avr-gcc-4.8.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha
@@ -0,0 +1 @@
+220662c5411e34dd1e16c181f883b6b77824a942
diff --git a/build/linux/avrdude-6.0.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha b/build/linux/avrdude-6.0.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha
new file mode 100644
index 00000000000..6d87ebcafe9
--- /dev/null
+++ b/build/linux/avrdude-6.0.1-arduino5-armhf-pc-linux-gnu-glibc2.13.tar.bz2.sha
@@ -0,0 +1 @@
+b5968416647e79f5c395bf2a9ba000127dacc9da
diff --git a/build/shared/lib/preferences.txt b/build/shared/lib/preferences.txt
index 26ac20ddbd4..8657dd50b27 100644
--- a/build/shared/lib/preferences.txt
+++ b/build/shared/lib/preferences.txt
@@ -274,3 +274,10 @@ serial.debug_rate=9600
 
 # default chosen language (none for none)
 editor.languages.current = 
+
+# Debugging/Development Preferences
+# ---------------------------------
+
+# Disable signature check on packages_index.json, use only for
+# development/debugging purposes. Do not enable in production.
+#allow_insecure_packages=true