How to Set Up a Smartwatch to Scan a Libre (without a Phone or Reader)

Scan a Libre with a Sony Smartwatch 3. No phone required!

Objective: Set up a smartwatch, specifically a Sony Smartwatch 3 (SSW3), to SCAN a 10-day Libre sensor WITHOUT a phone or Libre reader. The watch is “stand-alone,” meaning that the watch does not need to be paired with a phone. At the time of writing, this is the only smartwatch that can be used as a stand-alone scanner for the Libre. Additionally, note that the Libre sensor must be a 10-day sensor. 14-day sensors are not compatible.

Readings from the Libre are transferred to the watch via NFC, unlike other CGMs which use Bluetooth. Setting up a SSW3 to use NFC is complicated, which is why I thought I would write a guide as I go through the process.

Bonus: If you use a smartwatch as a scanner, you only need to wait 1 hour for the sensor to warm up.

What this article is NOT about: You can set up a variety of Android smartwatches to act as stand-alone collectors for either a Dexcom CGM or a Libre with a MiaoMiao or Bluecon on top using xDrip+. Notes on how to do this and troubleshooting are HERE. At the time of writing, you cannot use an Apple Watch as a stand-alone reader for a CGM.

Wait, don’t you have a Dexcom G6? Why do you need a Libre? I’m doing a 4.4-mile open water swim later this year and want to be able to easily check my blood sugar. The Dexcom G6 uses Bluetooth to transmit data and thus has a range of only 1cm through water.

Why aren’t there more pictures in this guide? To be honest, this was a tough set up and I lost track of taking screenshots. If you have feedback or screenshots as you go through the process, let me know! I might also agree to set this up for someone in exchange for the chance to take more photos. :-)

Requirements:

• Sony Smartwatch 3 (eBay $80-$100 used)
• Sony Smartwatch 3 data/charging cable
• United States: Freestyle Libre 10-day sensor. 14-day sensors WILL NOT WORK.
• Europe/Canada: Freestyle Libre 14-day sensor. Libre 2 sensors WILL NOT WORK.
• LibreLink app on iPhone or Android OR Libre Reader device
• iPhone users: An Android phone to use during set up. It doesn’t need a SIM card. After set up, you won’t need it anymore. Hopefully you’re like me and have a friend who has an old Android phone sitting in a drawer. (Thanks, Nate!)
• Time and patience — 1 hour assuming everything goes perfectly

Overview of the Steps (clickable links):

• Step 1: Insert Libre sensor and initialize the sensor using LibreLink or reader.
• Step 2: Download Wear OS app on your iPhone or Android and pair with your watch.
• Step 3: Download Android Studio.
• Step 4: Put your watch in developer mode.
• Step 5: Check your build number. Downgrade watch if necessary. (LONG)
• Step 6: Update the watch to build LCA43.
• Step 7: Install NFC.
• Debugging Step: If anything goes wrong, go into Fastboot.
• Step 8: You successfully set up the watch. Now install the Glimp app.
• Oh no! Something went really wrong.

I highly recommend printing these instructions and checking off the steps as you go. Read each step before you implement it. You can also read these simplified instructions which is what I was working off of. Finally, take a look the bottom of this page, where I lay out what to do if something goes really wrong. For example, you get the dead android error.

Poor little Android. :-( Look! A box of Novolog in the background.

Step 1: Insert Libre sensor and initialize the sensor using LibreLink or reader. The Glimp app, which we will be using to scan the Libre, CANNOT start a new sensor. You must do this with the LibreLink app or the Libre reader. Download the LibreLink app from the Apple App store or Google Play store. Create an account and go through the sensor insertion instructions. Then start the sensor. The warm-up countdown is 12-hours, but you will be able to see your blood glucose (BG) using the watch after 1-hour of warming up.

The LibreLink app will walk you through inserting the sensor.

Step 2: Download Wear OS app on your iPhone or Android and pair your watch. I have an iPhone so I went to the apple store and searched for “Wear OS.” Download and open the app. Then start up your watch and go through the pairing instructions.

Step 3: Download Android Studio.

• Go HERE and download Android Studio. You could also download the SDK only to save hard disk space, but I could not get this to work. (No idea what’s wrong. My javac was working correctly and environment variables set…)
• Install Android Studio by double clicking the application file in your Downloads folder. After installing, open the Android Studio app and go through the standard configuration with default options. This will take a bit.

Step 4: Put your watch in developer mode.

• Hold down the side button on the watch.
• Scroll to “Settings” then “About.”
• Tap where it says “Build number” seven times until it says “You are now a developer.”
• Go back to “Settings” then “Developer Options” -> “ADB debugging” and enable.

Step 5: Check your build number. Downgrade watch if necessary.

This is a very long, critical step. There are 10 parts (5.1–5.10).

Step 5.1: Check your watch’s build number.

• On the watch go to “Settings” -> “About”. Scroll down until you see “Build number”. If your build number starts with “L,” you can skip everything after step 5.5 and proceed to Step 6.

Step 5.2: Set up the ability to send files to your watch by installing Android ADB (debugging) and ADB drivers for the watch.

• Plug your SSW3 into your computer using the power/data cable.
• Note: If you are on a Mac (OSX), try the instructions HERE instead of the next two steps. No guarantees, but worth a shot. Let me know if it works for you.
• [Windows Only] Install the Google USB driver and find the path to your Android SDK. Open Android Studio. Click “Configure” -> “SDK Manager”. In the middle at the top it will say “SDK Tools”. Click this then check “Google USB Driver” then “Apply”, “OK”, “Accept”, and install. You’ve now installed the driver. Next, at the top it will show the path to the SDK. Copy this path.
• Open the command prompt in administrator mode (Windows) or terminal (Mac). To do this in Windows, search for “Command Prompt” then right click “Run as Administrator.” Type (without quotes) “cd ” and the path to the SDK plus a slash and “platform-tools”, (e.g. “cd C:\Users\laure\AppData\Local\Android\Sdk\platform-tools”).

Step 5.3: Authorize ADB on your watch.

• In the Command Prompt/Terminal, type “adb devices”. It will then print the name of your device and “XXXXXX unauthorized” where XXXXXX is the name of your device.
• Back on your watch, which is plugged into your computer, you should now see a screen where you can tap “Authorize debugging”. Tap that on the watch.
• Type “adb devices” in the Command Prompt/Terminal again. It should then say that the device is authorized.

Step 5.4 [Windows only]: Update the drivers for the watch with the ADB drivers.

• [Windows Only] Search for “Device Manager” in the start menu. Open the Device Manager. Scroll to “Universal Serial Bus devices” at the bottom of the list, click the arrow, right click on “SmartWatch3” -> “Properties”

This is what the device manager looks like.

• [Windows Only] Update the driver with the Android ADB driver. Click “Driver” -> “Update Driver” -> “Browse my computer for Driver software” -> “Let me pick from a list of available drivers…” from the SSW3 Properties menu. Then click “ADB Device Interface” (or something that sounds similar/contains ADB) and “Next”. There will be an installing screen and then “Windows has successfully updated your drivers.” You will then have to restart your computer.
• [Windows Only] Open the Command Prompt as administrator again. [Windows Only] Change the directory to the platform tools folder again (e.g. “cd C:\Users\laure\AppData\Local\Android\Sdk\platform-tools”). Type “adb devices” again and enable debugging again on the watch. Type “adb devices” again.

Step 5.5: Enable Fastboot so we can load a file transfer system (TWRP) on the watch in Step 5.7.

• Run Fastboot. In the Command Prompt/Terminal type “adb reboot bootloader”. On your watch it should now say “Running Fastboot on the screen.
• Type “fastboot oem unlock”. The command prompt will then print “< waiting for any device >”.
• Make sure you are in the Command Prompt/Terminal window and hit “Ctrl + C” (no plus sign — hold down the control key then press the C key).
• [Windows Only] Open the Device Manager like we did before. Under “Other devices” you will now see “tetra”. Just like before, right click on properties then “Driver” -> “Update Driver” -> “Browse my computer for Driver software” -> “Let me pick from a list of available drivers…”. Windows does not recognize the device type so now click “Universal Serial Bus devices”. Then click “Android ADB Interface” (or similar) under “Google Inc” and “Next” and “Yes”. There will be an installing screen and then “Windows has successfully updated your drivers.” You will then have to restart your computer.
• Back in the Command Prompt/Terminal, type “fastboot oem unlock” again. It will say “Device still locked.”
• Repeat — type “fastboot oem unlock” a second time. The command prompt will now say “Finished.”

Step 5.6: Download files to transfer to the watch and copy to relevant location.

• Download the files from HERE in your web browser. You can click on the arrow next to the file name “swr 50 fix” then you will see the option to download the whole folder. Then go to your downloads folder and unzip the folder.
• In your computer’s file explorer, navigate to the Google Drive folder we downloaded and unzipped. Copy the all the files into the platform-tools folder if you are on Windows (e.g. “C:\Users\laure\AppData\Local\Android\Sdk\platform-tools”) or some other convenient location if you are on a Mac. If you are on a Mac, back in the Terminal make sure you type “cd path/to/folder” where the path is the path to the convenient location you copied to.

Step 5.7: Start up the TWRP system on the watch to get ready to install the downgraded watch operating system.

• Type the four lines commands below (press enter between each) in the Command Prompt/Terminal.
• fastboot format cache
• fastboot format userdata
• fastboot flash recovery SWR50.img
• fastboot boot twrpnew.img
• The phone will now reboot and you should see a menu on the watch that looks like below. (Not my photo.)

This is what the TWRP menu looks like.

Step 5.8: Reformat your data, cache, and system folders to Ext4.

• You may not need to do the next few steps on your watch, but I needed to, so do the next few steps as a precaution.
• In the TWRP menu, tap “Wipe” -> “Advanced Wipe”
• Click the data folder then “Repair or Change file system” (NOT swipe to wipe)
• “Change File Sys” -> “Ext4”.
• Press the back button and repeat the above steps for the system and cache folders.

Step 5.9: Push and install the downgraded watch operating system.

• Back in the Command Prompt/Terminal, type “adb push SWR50.zip /sdcard/”. In the Command Prompt it will show the loading percentages and then “SWR50.zip: 1 file pushed…”
• Press “Install” in the TWRP menu on the watch.
• Go to the folder sdcard.
• Press SWR50.zip and install.
• After installation, press back.
• Go to “Wipe” and swipe to factory reset. Reboot device (“Reboot” -> “System”).

Step 5.10: Pair the downgraded watch with your Android phone.

• iPhone users, you must switch to Android now. On your Android, go to the Google Play store and download Wear OS.
• Try pairing the downgraded watch. If it doesn’t pair (this happened to me), try downgrading the Wear OS to Android Wear by going to https://tinyurl.com/old-wear-apk on your Android phone (link to my personal Dropbox). Download and install the apk by clicking on it. You’ll notice the app is now the old Android Wear instead of Wear OS. Open Android Wear and attempt to pair again.
• Repeat putting the watch into debug mode. On the watch go to “Settings” -> “About” and tap “Build number” seven times until it says “You are now a developer”.
• Go to “Settings -> Developer options -> ADB debugging” and enable.

Step 6: Update the watch to build LCA43

• Plug your watch back into the computer.
• Go to “Settings” -> “About” and take a look at your build number. If you had to downgrade your watch, the build number should now end in the letter “P.” We will be updating the watch three times. The first update will take the build number from “P” to “K.” The second update will go from “K” to “D.” The third will go from “D” to “LCA.” It is VERY IMPORTANT that you stop after going to LCA. If you did not need to downgrade the watch, make sure you stop at the “LCA” build number from whatever build number you are on.
• Go to “Settings” -> “About” -> “System Update” and start the update. This can take a while.
• Repeat the system update two more times until your build number is LCA43.
• DO NOT PROCEED TO STEP 7 IF YOU ARE NOT ON BUILD LCA43. You will spend hours trying to repair the watch. It is very annoying. (Speaking from experience.)

Step 7: Install NFC.

• Download file tetra_nfc_LCA43_0.2.zip from http://forum.xda-developers.com/smartwatch-3/orig-development/sony-smartwatch-3-nfc-support-package-t3219713
• Copy the file into your “platform-tools” folder or the convenient folder (Mac) you had before. Make sure you “cd” to that folder.
• In the Command Prompt/Terminal, try “adb reboot bootloader” and hopefully you will go into “Running Fastboot” like before. However, if this fails (it did for me) go to the “Debugging Step” below to go into Fastboot then proceed to next bullet.
• In Command Prompt/Terminal type the following commands.
• fastboot oem unlock (Note: will already be unlocked if you needed to put the watch in Fastboot.)
• fastboot oem unlock (Yes, twice)
• fastboot boot twrpnew.img
• adb push tetra_nfc_LCA43_0.2.zip /sdcard/
• On the watch you should see a menu. Press “Install” and locate the file under sdcard. Install it, then reboot.

Debugging Step: If anything goes wrong, go into Fastboot.

• Hold power button until watch turns off.
• Unplug watch from computer.
• Hold power button until a blue screen appears. DO NOT INSERT USB! (Yes, I know it tells you to)
• Double press power button. Now the screen should say “Fastboot” with a black background.
• Double press power button again. The screen should say “Running Fastboot” with a white background.
• Plug watch back to the computer.
• Note: you can use this same method to go back to Step 6 if something goes really wrong or instead of selecting Fastboot, do a factory reset and start again.

Step 8: You successfully set up the watch. Now install the Glimp app.

• Go to the Google Play store on your Android phone.
• Search for Glimp and install.
• In the Wear OS app, select the Glimp watchface for the Smartwatch 3.
• Now back on the watch, you should see the watchface and the bar that says CGM. Tap the bar and just scan your Libre. That’s it.

Oh no! Something went really wrong.

If something goes really wrong, don’t fret. It is very difficult to brick these watches. First, do the steps listed in the “Debugging Step,” but instead of going into Fastboot, click through until it says factory restore. If that doesn’t work, download and install the Sony Xperia Companion app on your computer. Select “Software Repair” and check the box for Smartwatch 3. In my case, I actually had to load TWRP again via Fastboot, go through Step 5, and then repair the watch in Xperia. My first Xperia attempt to repair failed.