Vexnet Joystick port pinouts?

What are the pinouts for the RJ type connectors on the Vexnet Joystick?

If there is power and ground available, I’d like to make a wall-wart adapter to power the joystick.

The Program port appears to have the same pinout as the Serial port on the V0.5 Microcontroller except with RX/TX and the flow control lines reversed null-modem style. (documented here).

If you apply a regulated 5V supply to the Ground and +5 pins, the Vexnet joystick does light up and appears to work. Note that this bypasses the power switch and the “Joystick” led glows red, presumably since the battery supply is switched off and is therefore below the 5.5V threshold.

This appears to apply power “past” the internal regulator, so you should provide only well regulated 5V. I don’t know if this is bad for the joystick in the long term, and I don’t know if it effects any aspect of its operation.

As for the Competition connector, the pinout is described in this schematic.

Pin 7 is shown wired to ground, but it is the Competition Switch Detect pin; if it is grounded, then pins 2 & 3 control the game state and the Game LED is lit. If you leave it open, the Game LED stays dark and pins 2 & 3 are ignored.

I don’t know if pins 5, 6, and 8 have some other purpose, but they do show a low voltage that might imply logic-level signals on these pins.


  • Dean

Terrific, thanks! It makes sense that the programming port of the Vexnet Joystick is the same/Similar to the serial port of the V0.5microcontroller because the same programming cable is used for both.

So a regulated 5v wall wart, driving plus on pin2 and ground on pin4 should be able to supply power all day in a classroom setting, or BEST competition “tower power” to the joystick, eliminating the need for frequent battery swaps in the joystick. Downside is that your “wireless” joystick now has a tether wire for power.
Alternate idea for battery power is a 7.2v battery pack to a 5v regulator dongle to a programming plug, to get the full wireless benefit, at the cost of heavy dangling battery.

Someone on another thread was looking for an “Estop” button.
The programming cable has an “Estop” button function that works for V0.5.
If it works on the Vexnet Joystick, that might be a path to implementation…

Quoting from your link:

Do you mean the button on the orange box in the middle of the programming cable? I’m not sure what that actually does - I’m not sure if it would reliably stop a robot. There isn’t a reset pin or other guaranteed shutdown available on the microcontoller that I’m aware of.

An estop from the remote control could simply plug into the competition port and ground pins 7 & 3. If the robot was linked via VEXnet, this should disable it.

If you want a real Estop on the robot, the best thing to do would be get a matched pair of battery leads (male & female) and make an extension with a switch in the middle. One of these would do nicely, or perhaps one of these missile-switch covers and a basic toggle switch if you prefer the classic “smack to stop” action. They have that switch cover in a variety of styles, including a very cool looking Carbon Fiber.


  • Dean

Actually, looking back over my notes, I don’t think it is wired null-modem style. I think it is wired identically to the V0.5 serial port, which makes sense given that the same programming cable is used for both.

This seems reasonable, though I want to reiterate that I don’t know if long-term use would be harmful to the joystick.

I’ve also noticed that the joystick receives power from the USB A-A tether cable. It may be possible to inject regulated 5V power to that port by tapping into the power wires of a USB extension cable. That has the disadvantage of coming between the joystick and the VEXnet key, but at least it is known to be a supported power inlet for this device.


  • Dean

I thought of that as well, but it is more painful to have to unplug the key, insert the T extension, replug the key. You’d have trouble at a tournament with teams forgetting to take their keys back with them.
Hmm, can you leave the key stuck in the T-power-tapped USB extension cable, so that every team at that field position uses the same vexnet key in the joystick? Since joysticks and cortex were previously hard-linked, it should work fine in theory.

I think that would work.

I don’t know if the tournament organizer would want to accept the responsibility of becoming part of the RF link between the robot and the driver, though. Many forum posts refer to switching VEXnet keys out to avoid overheating, etc., so teams are likely to have strong opinions about that becoming a field-controller function. (especially if they encounter link problems during a match).


  • Dean