I recently got an FPV board camera with one of the little in-line joysticks to adjust the settings via OSD. The only problem is that the joystick has a DC barrel jack for power and a BNC connector for video, so I would have to re-wire everything to adjust settings in the field. Today, I built a harness to allow me to plug in just the joystick, while leaving power and video run out to the vTX, so I can easily adjust the OSD in the field, while viewing video in real time through the goggles. (EDIT: Not while flying, obviously!)
The connector on the back of the camera is a four-pin micro-molex, or something like that. It has the following pins: power, ground, video, OSD. The key to understanding how the harness works is that the OSD works by putting varying resistance between the OSD lead and ground. So, for example, if you click the joystick right, there is 2.2 kOhms between OSD and ground. If you click the joystick left, there is 15 kOhms. Etc... (Those values made up as I didn't write the actual values down.) So, basically, the camera measures the resistance on the OSD lead and that's how it detects joystick presses.
Therefore, here is what we need. We need a Y harness that has power, ground, and video on one end and OSD and ground on the other end. That way, we can plug in the power, ground, and video to the vTX, and the OSD and ground to the joystick at the same time.
It looks like this:
I apologize for my over-exposed photo, but you can see the two servo connectors coming from the camera. One of them goes to the servo lead pictured, which is actually coming from the vTX. The other branches off ground from the first one and contains the white OSD lead from the original connector.
Here's a diagram:
The joystick side looks the same, but with the opposite gender of servo connectors. I like to buy 10 cm extensions and then cut them in half just to get the connectors.
This setup allows that cable to be used for power/video out if so desired, just un-plug the vTX from the appropriate connector and plug the joystick cable in instead.
The connector on the back of the camera is a four-pin micro-molex, or something like that. It has the following pins: power, ground, video, OSD. The key to understanding how the harness works is that the OSD works by putting varying resistance between the OSD lead and ground. So, for example, if you click the joystick right, there is 2.2 kOhms between OSD and ground. If you click the joystick left, there is 15 kOhms. Etc... (Those values made up as I didn't write the actual values down.) So, basically, the camera measures the resistance on the OSD lead and that's how it detects joystick presses.
Therefore, here is what we need. We need a Y harness that has power, ground, and video on one end and OSD and ground on the other end. That way, we can plug in the power, ground, and video to the vTX, and the OSD and ground to the joystick at the same time.
It looks like this:
I apologize for my over-exposed photo, but you can see the two servo connectors coming from the camera. One of them goes to the servo lead pictured, which is actually coming from the vTX. The other branches off ground from the first one and contains the white OSD lead from the original connector.
Here's a diagram:
The joystick side looks the same, but with the opposite gender of servo connectors. I like to buy 10 cm extensions and then cut them in half just to get the connectors.
This setup allows that cable to be used for power/video out if so desired, just un-plug the vTX from the appropriate connector and plug the joystick cable in instead.
