Convert device elf binary to hex binary

Missed a step in generating the binaries for the teensy - gcc just makes an elf file, but we need to run one final command to convert it into the .hex format that can be loaded onto a teensy

.github/workflows/build-device/action.yml

@@ -22,7 +22,7 @@ inputs:
 outputs:
   binary-path:
     description: Path to the compiled binary
-    value: ${{ steps.retrieve-binary-path.outputs.binary-path }}
+    value: ${{ steps.convert-elf-to-hex.outputs.hex-path }}
 
 runs:
   using: "composite"
@@ -43,14 +43,22 @@ runs:
 
     - id: retrieve-binary-path
       shell: bash
-      name: Retrieve Binary Path
+      name: Retrieve binary Path
       run: |
         PATH=$(cat $HOME/binaries.txt)
         echo "Path is $PATH"
         echo "BINPATH=$PATH" >> $GITHUB_ENV
         echo "::set-output name=binary-path::$(echo $PATH)"
 
+    - id: convert-elf-to-hex
+      shell: bash
+      name: Convert Elf binary to Hex
+      run: |
+        $HOME/arduino_ide/arduino-${{ inputs.arduino_ide_version }}/hardware/tools/arm/bin/arm-none-eabi-objcopy -O ihex -R .eeprom ${{ steps.retrieve-binary-path.outputs.binary-path }} $HOME/device.hex
+        echo "::set-output name=hex-path::$(echo $HOME/device.hex)"
+
     - shell: bash
       name:  Display binary path to user
       run: |
-        echo "From Steps: ${{ steps.retrieve-binary-path.outputs.binary-path }}"
+        echo "Elf: ${{ steps.retrieve-binary-path.outputs.binary-path }}"
+        echo "Hex: ${{ steps.convert-elf-to-hex.outputs.hex-path }}"