diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 56af0b1..f8efcf9 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -144,3 +144,65 @@ jobs:
         ccache -M 400M
         ccache -c
 
+  cygwin:
+    runs-on: windows-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        boards: [arm-12-win, sim]
+
+    steps:
+    - run: git config --global core.autocrlf false
+    - name: Checkout nuttx repo
+      uses: actions/checkout@v2
+      with:
+        repository: apache/incubator-nuttx
+        path: nuttx
+        fetch-depth: 0
+
+    - name: Fetch nuttx tags
+      run: |
+        cd nuttx
+        git fetch --tags
+
+    - name: Checkout apps repo
+      uses: actions/checkout@v2
+      with:
+        repository: apache/incubator-nuttx-apps
+        path: apps
+        fetch-depth: 0
+
+    - name: Checkout testing repo
+      uses: actions/checkout@v2
+      with:
+        repository: apache/incubator-nuttx-testing
+        path: testing
+
+    - name: Restore tools cache
+      id: cache-tools
+      uses: actions/cache@v2
+      env:
+        cache-name: ${{ runner.os }}-cache-tools
+      with:
+        path: prebuilt
+        key: ${{ runner.os }}-tools-${{ hashFiles('./testing/cibuild.sh') }}
+
+    - name: Install cygwin base packages with chocolatey
+      shell: pwsh
+      run: |
+        choco install --no-progress cygwin --version 3.1.4
+        choco install cyg-get
+    - name: Install Build Requirements for Cygwin
+      run: |
+        cyg-get make gcc-core gcc-g++ flex git bison byacc gperf gdb unzip awk `
+                automake-1.15 autoconf wget xxd libmpc-devel libncurses-devel `
+                libmpfr-devel zlib-devel patch
+    - name: Set Cygwin PATH env
+      run: |
+        echo '::set-env name=PATH::C:\tools\cygwin\bin;C:\tools\cygwin\usr\bin'
+        echo "::add-matcher::nuttx/.github/gcc.json"
+    - name: Run builds
+      shell: cmd
+      run: |
+        C:\tools\cygwin\bin\bash.exe --noprofile --norc -e -o pipefail -c "cd testing &&./cibuild.sh -i testlist/${{matrix.boards}}.dat"
diff --git a/cibuild.sh b/cibuild.sh
index 928ea8f..3c86610 100755
--- a/cibuild.sh
+++ b/cibuild.sh
@@ -32,9 +32,18 @@ nuttx=$WORKSPACE/nuttx
 apps=$WORKSPACE/apps
 tools=$WORKSPACE/tools
 prebuilt=$WORKSPACE/prebuilt
-os=$(uname -s)
 EXTRA_PATH=
 
+
+kernel="$(uname -s)"
+case $kernel in
+  Linux*)   os=Linux;;
+  Darwin*)  os=Darwin;;
+  CYGWIN*)  os=Cygwin;;
+  MINGW*)   os=MinGw;;
+  *)        os="UNKNOWN:$kernel"
+esac
+
 case $os in
   Darwin)
     install="python-tools u-boot-tools elf-toolchain gen-romfs kconfig-frontends arm-gcc-toolchain riscv-gcc-toolchain xtensa-esp32-gcc-toolchain avr-gcc-toolchain c-cache binutils"
@@ -44,6 +53,9 @@ case $os in
   Linux)
     install="python-tools gen-romfs gperf kconfig-frontends arm-gcc-toolchain mips-gcc-toolchain riscv-gcc-toolchain xtensa-esp32-gcc-toolchain rx-gcc-toolchain c-cache"
     ;;
+  Cygwin)
+    install="gen-romfs kconfig-frontends arm-gcc-toolchain"
+    ;;
 esac
 
 function add_path {
@@ -115,6 +127,9 @@ function kconfig-frontends {
   add_path $prebuilt/kconfig-frontends/bin
 
   if [ ! -f "$prebuilt/kconfig-frontends/bin/kconfig-conf" ]; then
+    if [ ! -d "$tools" ]; then
+      git clone https://bitbucket.org/nuttx/tools.git $tools
+    fi
     cd $tools/kconfig-frontends
     ./configure --prefix=$prebuilt/kconfig-frontends \
       --disable-kconfig --disable-nconf --disable-qconf \
@@ -142,22 +157,33 @@ function bloaty {
 
 function arm-gcc-toolchain {
   add_path $prebuilt/gcc-arm-none-eabi/bin
+  urlbase="https://developer.arm.com/-/media/Files/downloads/gnu-rm/9-2019q4/"
+  releasebase="gcc-arm-none-eabi-9-2019-q4-major"
 
   if [ ! -f "$prebuilt/gcc-arm-none-eabi/bin/arm-none-eabi-gcc" ]; then
-    local flavor
+    cd $prebuilt
+    local filename
     case $os in
       Darwin)
-        flavor=mac
-        ;;
+        filename="$releasebase-mac.tar.bz2"
+        wget --quiet $urlbase/$filename
+        tar jxf $filename
+        mv $releasebase gcc-arm-none-eabi
+	;;
       Linux)
-        flavor=x86_64-linux
+        filename="$releasebase-x86_64.tar.bz2"
+        wget --quiet $urlbase/$filename
+        tar jxf $filename
+        mv $releasebase gcc-arm-none-eabi
+        ;;
+      Cygwin)
+        filename="$releasebase-win32.zip"
+        wget --quiet $urlbase/$filename
+	mkdir -p gcc-arm-none-eabi
+        unzip -qq $filename -d ./gcc-arm-none-eabi
         ;;
     esac
-    cd $prebuilt
-    wget --quiet https://developer.arm.com/-/media/Files/downloads/gnu-rm/9-2019q4/RC2.1/gcc-arm-none-eabi-9-2019-q4-major-${flavor}.tar.bz2
-    tar jxf gcc-arm-none-eabi-9-2019-q4-major-${flavor}.tar.bz2
-    mv gcc-arm-none-eabi-9-2019-q4-major gcc-arm-none-eabi
-    rm gcc-arm-none-eabi-9-2019-q4-major-${flavor}.tar.bz2
+    rm $filename
   fi
   arm-none-eabi-gcc --version
 }
@@ -322,6 +348,9 @@ function binutils {
     case $os in
       Darwin)
         brew install binutils
+	# It is possible we cached prebuilt but did brew install so recreate
+	# simlink if it exists
+        rm -f $prebuilt/bintools/bin/objcopy
         ln -s /usr/local/opt/binutils/bin/objcopy $prebuilt/bintools/bin/objcopy
         ;;
     esac
@@ -391,6 +420,9 @@ function run_builds {
     Linux)
       ncpus=`grep -c ^processor /proc/cpuinfo`
       ;;
+    Cygwin)
+      ncpus=`grep -c ^processor /proc/cpuinfo`
+      ;;
   esac
 
   options+="-j $ncpus"
diff --git a/testlist/arm-12-win.dat b/testlist/arm-12-win.dat
new file mode 100644
index 0000000..e725df2
--- /dev/null
+++ b/testlist/arm-12-win.dat
@@ -0,0 +1,5 @@
+/arm/stm32f0l0g0,CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW
+
+/arm/stm32f7,CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW
+
+/arm/stm32h7,CONFIG_ARMV7M_TOOLCHAIN_GNU_EABIW