GDT Administrator

IOS App Overview


The GDT Administrator is used to setup and manage a WallGauge GDT.  GDT stands for Gauge Data Transmitter and it is a small printed circuit board (PCB) fitted to a Raspberry Pi Zero’s expansion header.  The GDT-PCB host two infrared LEDs that beam gauge data to all WallGauges (within 20 feet or so) in the same room.  The GDT-PCB also has a red and green LED as well as a button that is used to enable pairing with your smartphone.

In this guide I will walk you through the functions of the GDT Administrator.

  1. Initial load.

    1. When the app is first launched the user is prompted by IOS to allow the connection to the iPhone’s Bluetooth radio  The text is “Please select OK to allow this app to securely communicate and manage your Gauge Data Transmitter.”  

    2. Then the user is asked to agree to our terms of service and privacy policy with a link to

    3. Once the user agrees to the terms they land on the home screen.  It is a list view displaying the GDTs that are within range.  If no GDTs are within range a spinning refresh icon is shown until they are.

    4. The home screen also has a little i in the title bar that brings up a pop over from the bottom giving the user links for Help, Terms & Conditions, and our Privacy Policy.

  2. Connect and setup GDT

    1. When a new GDT appears in the home screen a user can tap on it and they will be presented with the Secure Connection setup view.  This view explains what the connection is for and how to accomplish it.  The user is instructed to push the pairing button on the GDT-PCB.  This enables the pairing process on the phone.  The user then pushes a button labeled “Start Pairing Process” on the smartphone.  This triggers the radio in the iPhone to bind with the GDT and displays the IOS message: “Wall Gauge Data Transmitter would like to pair with your phone”. 

    2. After pairing with the GDT the next screen explains this is a persistent encrypted connection and from now on the phone will use this secure connection to communicate with the GDT.  It then presents the user with an option to return home or continue on with the setup.  If the GDT has already been setup and the user is adding a second phone they can return home.

    3. When the user taps the Continue setup button they are presented with a screen allowing them to give this GDT a name and a contact eMail address.  This name will show up in the home screen so a user with multiple GDTs can identify them. The eMail address is used to send security alerts and notifications.

    4. The next screen starts the network setup of the GDT.  I explain the risks of having an IOT appliance connect to your home network and suggest they connect it to a guest network.  

    5. As the Select a Network screen loads the GDT makes a quick scan of available wireless networks.  The GDT Administrator app will then present a list view.  The user can tap on a network and is taken to the set New Network screen.  Here the user is asked for the wireless network passcode. When the user pushes connect a running log is visible on the bottom half of the screen showing the user the status of the GDT’s connection to the selected wireless network.  If the GDT successfully connects to the wireless network the user is presented with a pop up letting them know.  If not they can try again or go back and pick another network.  

    6. Once a wireless network has been connected, the user is taken to the GDT Setup Complete screen. This screen gives the user some general information about their gauge and how to manage it. 

  3. Gauge Management: Once a GDT has been bound to the iPhone, its’ padlock icon on the right will change to a locked green padlock.  This lets the user know they have a secure connection established and when they tap on this GDT they will be taken to the gauge administration section of the IOS application.  The administration section is a tab view with three tabs: Overview, Network Setup, and Add / Remove Gauge

    1. Overview tab

      1. The Overview tab has information about this GDT’s Device Name, Location, Network connection and overall system status.  It has a list view with the WallGauges installed on this GDT.  Often there will only be one WallGauge but up to 10 WallGauges can be installed on a GDT. At the top of the screen in the menu bar there are two icons one is a filter icon (three horizontal lines) and the other is a maintenance icon (hammer).  

        1. A tap on the filter icon will add a new section to the list view showing the core applications and OS version of the GDT.  This allows the user to see the current version of the software the GDT is running.  If the user taps on one of the core Applications they are taken to a screen that allows them to check for updates and update them.  This is not necessary as the GDT has a nightly maintenance schedule that will update all installed gauges and core applications if an update is required. However, if the user wants to update an app now they have that option.

        2. A tap on the maintenance icon (hammer), pops up an Admin Commands menu.  The user is presented with the option to reboot or shutdown the GDT, Set a new GDT location / name, Enable the uploading of diagnostic logs, Enable the beta test mode, and to turn the midnight Auto update maintenance on and off. 

      2. When a user selects a WallGauge in the “active Gauges” list they will be taken to the Admin screen for that WallGauge.  There they will see the WallGauge’s application version, last gauge value, and an estimated battery replacement date.  Some WallGauges have items that need to be configured and others just work with defaults.  This is the place users will manage those settings. For example to calculate when the batteries will need to be replaced the user must enter the “Battery Last Replaced” date.  By tapping on that in the list view they are presented with a date picker allowing them to pick the date the batteries were replaced.  

        1. If the user taps on the filter icon in the header bar they will see more details about that gauge. 

        2. If the user taps on the log icon (eye) in the header a log showing that gauges data pops up.  This screen can be left open and a running log of gauge values will be shown.  

    2. Network Setup tab

      1. When the user taps on the Network Setup tab they are taken to a screen that allows them to change the network settings of the GDT.  At the top of the screen they see the current network connection, IP address, Mac address, and connection status to the Internet. Below the summery section is a list view of networks in range. To change the network the GDT is connected to, the user can tap on one of the options. They will then be presented with a screen prompting them for a passcode and a button allowing them to connect. 

    3. Add / Remove Gauge tab

      1. When the user taps on the Add / Remove Gauge tab they are presented with a list view of all available gauges that can be installed on this GDT.  The gauge list is colored coordinated and gauges in Green can be added and the ones in Red are already installed and can be removed.  To add or install a gauge the user taps on one of the gauges and is presented with a pop up with additional information and buttons that allows them to delete the gauge or add it to the system.  When a user adds or deletes a gauge they are taken to a log view allowing them to monitor the process.  Gauges that are added will show up in the overview tab with there status. 


IOS App Data

This app is built on the CoreBluetooth API.  Most of the external data the app uses is from the GDT.  The data is read or written with secure encrypted characteristics.  There are only two characteristics that are not encrypted and they are used to help setup and bind the GDT to the IOS device.  No user data (other than the GDT name) is ever sent over a non encrypted characteristic.  The data the IOS app uses that is not over the CoreBluetooth API is from our web site and is general information pertaining to our Terms and Conditions, Privacy policy, and details about a WallGauge. 


The Wall Gauge Data Transmitter shows up in the MY DEVICES section under Bluetooth settings on the iPhone and iPad.  The user can remove the connection at any time by tapping on the more information icon and selecting Forget This Device.