Adding HDZero FPV to the FT Gremlin Guardian v2

by Josh Cook, FliteTest | July 4, 2024 | (0) Posted in How To

Converting the Flite Test Gremlin Guardian v2 to HDZero

With digital FPV Systems getting better, more compact and more affordable, looking to upgrade your fleet becomes more feasible.  I took the opportunity to try out the HDZero Eco Bundle on the Flight Test Gremlin Guardian v2 to bring this amazing quad up to the digital HD era.  If you’re familiar with a little bit of soldering, it’s a pretty straightforward task.  And you get OSD!

Skills Required

  • Soldering

  • 3D Printing

  • Betaflight

Tools and Parts

Before we start, make sure to have the following:

  • Flite Test Guardian Gremlin v2

  • HDZero Eco Bundle

  • HDZero Monitor or HDZero Goggles

  • Soldering Iron

  • Solder

  • Soldering Helping Hands

  • Wire Strippers or Razor Blade

  • Heat Shrink Tubing (Extra Small) or Electrical Tape

  • Heat Gun, Dryer, or Lighter

  • Hot Glue Gun

  • Hot Glue Stick

  • 4 x 26-28 gauge silicone wire approximately 90mm (3.5 inches) long

    • 4 different colors would be ideal to keep the wires from being confused

    • These will be cut into two different lengths, 50mm (2 inches) and 40mm (1.5 inches)

    • The 40mm length can be harvested from the plug that comes with the HDZero Eco Bundle

    • If you still have the extra wires from your flight controller, there is a bundle of 4 wires 100mm long that can be used for this.

  • USB-A to Micro USB Data Cable

  • Betaflight Configurator

  • New HDZero Flite Test Guardian Gremlin Canopy 3D Print

Getting Started

While we’re working, go ahead and print out the new canopy for the HDZero Eco Bundle camera.  I linked to it on the Flite Test Forums up above.  It only takes a few minutes to print, and I recommend using PLA+, Tough PLA, or even PETG if you have it.  I chose to do mine out of PETG, it’s a little more durable as well as heat and UV resistant which for me is important since I live in Arizona.  But any of those materials will work.  If you don’t have a 3D printer, reach out to a friend for help!

If you’ve already built your Flite Test Gremlin Guardian v2 and have the Caddx Ant AIO Camera/VTX combo in there, the first step is to go ahead and remove the top plate, and desolder it from the flight controller.  Set that aside, along with the canopy that it sits in. You can use that for your next FPV build, whether a plane or a multirotor!  Also, go ahead and remove the stack nuts as well and set them aside somewhere safe (they’re super tiny!!).

Since the soldering iron is still hot, we need to desolder the camera on the HDZero Eco Bundle from the VTX.  We need to extend these wires by about 40mm to extend the reach so we can mount both the camera and the VTX where they need to be.  Take note of where the wires are soldered so we don’t get them mixed up.  Use the pictures below for reference.

Wire Lengths

From the four lengths of 90mm wire, we’ll need to trim these down to four lengths of 40mm and four lengths of 50mm.  As stated above, if you kept the extra wires and parts from your Flight Controller, there’s a bundle of 4 wires 100mm long that can be used for this.  You can also cut the wires from the plug that comes with the HDZero Eco Bundle for the 40mm segment since we will not need the plug on this project.

Strip about 2mm from one side of the 40mm length wires and tin them to prep them for the HDZero VTX.  On the other side, strip about 3mm to prep them for extending the camera wires.

Strip approximately 2-3mm from one side of the 50mm wires and tin them to prep them for the HDZero VTX.  On the other side, strip approximately 2mm and tin them to prep them for the flight controller.

You do not have to do this all at once.  If it makes sense for you to just do one side at a time, feel free to do that so you can keep the ends correct for the right purpose.  You can come back and reference this section as needed.

Extending the Camera Wires

Utilizing the 3mm sides of the 40mm wires, you’ll need to splice the wires together.  This is where the helping hands will come in handy to hold the wires together while you solder them.  Adjust the wires so the tinned ends are overlapping each other as seen below.

Take your time to align these properly so you get a good strong solder joint.  Once aligned, go ahead and put a solder bead to connect them.  Do this for the remainder of the camera wires.  Once completed, put your heat shrink over the joints.  The segments of heat shrink does not need to be long, just enough to cover the joint plus a few millimeters on either side.  When complete, the wires should look like the below image.

We can now turn our attention to soldering the wires back to the HDZero VTX.  Use your soldering iron to wet each pad and drop a bead of fresh solder on each to prep them.  Now you can solder each wire back.  Make sure you’re putting them back onto the correct pads.  Ensure that none of the wires are creating a short.  You can check this with an electrical multimeter if you have one handy.  Also, instead of having the wires route over the board as it originally comes, have the wires come off the edge of the board.  You can use the below picture for reference.

HDZero VTX to Flight Controller

Now, let’s turn our attention to the wires that need to go from the HDZero VTX to get power and information from the flight controller.  The 50mm wires will be used for this and will be routed under the VTX.  Take note of the pads 90 degrees around the VTX marked V / G / T / R.  Those markings stand for Voltage / Ground / Transmit / Receive respectively.

Take note of what color wires you put to each.  To keep it simple, I used red for voltage, black for ground, yellow for transmit, and white for receive.  Whatever color you decide to use, keep it in mind, because they won’t hook up to the flight controller in the same order.  Use your soldering iron to wet each pad with solder.  

As a reminder, we’ll be using the longer stripped side of the 50mm wires here.  Add each wire in sequence, again ensuring that you’re not creating any shorts between the wires.  The wires need to come off the edge of the board, just as the camera wires did.  See the below image as a reference.

Now comes adding those wires to the flight controller so that it can power the HDZero Eco Bundle.  For this, let’s pull the pinout for the flight controller to make sure we’re adding those wires to the right pads.  We’ll be using the pads highlighted in green, closest to the positive battery wire.

Ensure the prep these pads by wetting them with a bead of solder.  The easiest way is to work from the ground wire closest to the positive battery wire.  Just to mix things up a bit, instead of soldering the wires off the edge of the board as we have done up till now, the cleanest way is to solder these across the top of the flight controller.  Also, note that the Transmit wire from the HDZero VTX will goto the pad labeled RX1 on the flight controller while the Receive wire from the HDZero VTX will goto the pad labeled TX1.  This establishes the correct communication between the HDZero Eco Bundle and the flight controller.  See below image for reference.

That’s it for soldering!  Great job!  Make sure and turn off your soldering iron for safety purposes.

Wire Routing and Canopy

Putting the stack back together to route the wires is important so they don’t get caught up in the propellers.  Right now your HDZero VTX should be upside down with the Divimath chip facing down and the wires between the VTX and the flight controller going over the flight controller.  Go ahead and fold the VTX over so the wires are going under the VTX.

Before you put the HDZero VTX down on the stack, make sure and loop the wires under the front stack screw so they are also under the board.  Once done, go ahead and put the VTX on the stack screws, making sure that no wires are in between the gummies on the VTX and flight controller.

To put the camera into the new canopy, it’s easiest to come in from the side and just rotate the lens through the hole.  The canopy is keyed so the camera should lock into those divots.  Also keep in mind that the wires attached to the camera should be at the top.

To secure the camera, you can just put a little hot glue on the corners of the camera that have the screw holes.  If you find this isn’t enough, a little on the two edges of the board should help.  A little goes a long way. 

Also, as we look to install the camera to the frame make sure the wires for the camera are wrapped around the opposite side of the frame standoff from where the wires come out from between the two boards.

Notice that all the wires should be well away from the props and centralized around the stack as much as possible!  Don’t forget to put your stack nuts back on to secure the flight controller and VTX.  Also, make sure your VTX antenna is well away from the props.  You can put a dot of hot glue on it at the stack nut.  Don't glue it on the any of the IC Chips on the board, those get really hot. Leave the top plate off the Flite Test Gremlin Guardian v2 for now, so we can work in Betaflight to ensure that the flight controller is set to work with the HDZero Eco Bundle.

Setting up Betaflight

First, take your props off!  Plug in the USB to your computer and also into your flight controller.  Open up Betaflight and click the connect button at the top right.

Click on the “Ports” tab on the left of the screen.  You’ll recall that we wired up the HDZero Eco Bundle to TX1 and RX1 pads on the flight controller.  The number on those pad designations refers to what UART that equipment is on.  So, in this case, we need to work on UART 1.  

Make sure you click on “Configuration/MSP” slider and under the “Peripherals” column, click the dropdown where it says “Disabled” and change that to VTX (MSP + DisplayPort).

Click “Save and Reboot” at the bottom right of the window.  You should be all set up for HDZero now!  You can now go into the OSD Tab on the left and start setting up your OSD.  You can set this up however you like.  I recommend setting the OSD Video Format to AUTO or HD, it yields the best results.  Remember, you can click on the image on the specific elements and move them around to where you like them.  


With that, you should be good to go!  Don’t forget to put your props back on and secure the top plate!

The Flite Test Gremlin Guardian v.2 is a great aircraft perfect for STEM or just learning the basics of building and flying a multirotor.  Adding the HDZero Eco Bundle is the next step to the immersive world of FPV!


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Adding HDZero FPV to the FT Gremlin Guardian v2