FC <-> VMC Telemetry Cable
It's important that the FC and VMC can communicate with each other. This bi-directional communication will allow us to receive telemetry data from the FC and send data to it from the VMC. If you recall, in Phase I we communicated with the FC using a micro-USB cable connected to a PC running QGroundControl. What you will be able to do in Phase II is communicate over a WiFi network, which will make this process easier.
In addition to a wireless link between the VRC drone and QGC you will learn how to configure position hold capabilities using external cameras. You may have noticed in Phase I that the VRC drone required constant input from the pilot to maintain position in stabilized flight mode. With the assistance of these cameras you will be able to hover in position mode with ease! The cable we build in this section makes this all possible.
Locate the cable bundle in Box 5 and find the cable with a 4 pin JST-GH connector as seen below. The colors of the wires should be red, black, blue, and white.
Plug the JST-GH connector into the port labeled IR/TLM2 as shown in the photo below. Later on in the configuration process we will load new parameters from QGC onto the FC, which will enable communication over this port.
At the other end of the cable there are plastic connectors that will be removed. Each of the connectors has a small tab that can be lifted up using an X-Acto knife or small blade.
After lifting the plastic tab the connector should easily slide off the wire, exposing the metal leads. Remove the connectors for the black, blue, and white wires.
Each of these pins will be placed into a 2x20 crimp housing that can be seen below. There is a bag of several crimp housings located in Box 5. The wires should be placed in the housing so that the plastic tabs lock onto each of the metal leads as seen below. This will prevent the leads from accidentally being pulled out. Be sure to zoom in on the photo to see the proper orientation.
It's very important to make sure your wire order matches the photo below. The blue and white cables are what handle the transmit/receive signals between the FC and VMC. The black wire goes to ground.
It's a good idea to clip the red lead to keep your build nice and tidy. We recommend clipping this lead right where it comes out of the heat shrink. If you look closely at top left of the photo below, you will see where the red lead has been clipped.
The crimp housing is now complete. This will plug into the header pins on the VMC in the next section, so don't worry about plugging it in just yet. It's much easier to mount the VMC and plug this housing in later.
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