Our Permanent Solution to the Unreliable Micro USB Ports on the VEX V5 Controller

Link to Google Docs with write up:

Enjoy : )


@mavmaster21, before other mentors pound you with “this is totally illegal and unsafe” feedback, I would like to praise you for the willingness to jump the red tape and fix the * port, instead of just giving up and accepting its sad fate!

Audacity to open up controller and fix it despite of what adults are saying: A+

Documenting the project: A-

One thing that, I think, is missing from your documentation are the picture(s) or more detailed explanation of the damage to the existing microusb port. In my experience damaged metal walls are not the most frequent cause of failure. I more frequently observed individual damaged contacts or entire connector falling off the PCB, requiring resoldering. But this specific part may have different flaws - that’s why additional pictures of the failed ports would have been very nice.

Choosing yellow wire to carry +5v and red wire for one of the data signals: boo!

That’s not how it’s usually done. Red wire means power!


Finally, reusing one of the smart ports for the connection with different pinout and power specs: big boo!

The biggest problem could be if someone accidentally plugs a regular v5 motor wire into the modified smart port on your controller on one end and into V5 brain on the other end.

Do you know where the 12v power lines from V5 are going to be connected on the controller side?

Could it irrepairable damage either brain, or the controller, or both?

If I had to carry out such repair I would either use a standard USB dongle or some other sort of a pigtail connector, that reduces the chances of accidental erroneous connection.

In your case, unless you are going to redo the wiring, I highly recommend to hot glue your custom wire to the modified controller port - it will protect you from potential human error, but will still let you to melt the glue and replace the wire if necessary in the future.


@technik3k To start out, thank you for the reply. I’ll try here to go through and address each concern/ suggestion.

As an organization, we haven’t seen most of the modes of failure in the ports that you described. After our regional competition this Sunday we should have the time get some internal photos of the finished product and document the port damage more extensively.

Although the unconventional wire colors are not a great idea, using the layout that the V5 Smart Wire comes with means that the pin → color stays the same from the internal components to the final USB port making the wiring a bit more intuitive and easier to troubleshoot in our experience.

One solution to this could be adding a Polyfuse between the port and the FB1 and FB2 chipsets so that in the event that the controller is connected to the brain any damage could be mitigated. For the time being, the modified controller is in careful hands so hopefully no harm will come until we are able to make it more foolproof. Great idea about gluing the wire :+1: we are going to get on that ASAP.


I, probably the one @technik3k is referring to, am not going to trash because of “competition legal”, but agree with that the solution needs to be solid and follow electrical standards.

That said, the underlying problem is very real. I am shocked that that the only remedy is to send a V5 Brain back to VEX, for failure that is a number 1 use case, students attempting to plug a micro-usb cable into the V5 Brain. I would have hoped that VEX would release a sd card update option for firmware, or over the air (wifi), or tethered with V5 Joystick controller… but nothing has come from the company. VEX can and should do better.

Thank you for tackling this design flaw.


This is one more time where I would love a pad-compatible USB-C socket so it could be just soldered in place. They’re so much more durable than micro USB and do work with only those pads soldered down, but I’m yet to find a SMD USB-C port that has the same footprint as the standard micro USB. This would be so useful to PCB designers and tinkerers as I believe that USB-C is much better than micro and being able to swap without redesigning the whole board would be nice.

Anyways, nice project and a clever solution. I would’ve loved to see a LEMO connector coming out of the back of a V5 controller, but I understand that is very expenisve and would require difficult modification of the injection molded pieces.


I would have hoped VEX would release schematics and documentation for the V5, made replacement micro-USB ports available, or at least link to where they are, and provide instructions for how to safely repair the brain.

But hey, that’s just me.


What was the reason that you have rejected magnetic usb cables, may I ask?

That worked well for us for the past three years.

this solution appears to be a way to deal with a controller whose port has already failed. And I must say its definitely worth it for a controller that would otherwise be entirely useless. But for an unbroken controller, definitely better to use a magnetic usb cable so that the controller is still competition legal.

I will say though, if it’s possible to return a broken port controller and receive a replacement, that might be the better option so you can then prevent that one from breaking. I don’t know what vex’s policy on returning/replacing v5 components are though so this might not be possible.

all in all, I’d say this seems like a great solution for a team with a broken controller who has some competence with electronics, a functional but competition illegal controller is better than a useless controller after all.


That is what they said:

If they go to the extremes of desoldering components off the PCB, I would remove damaged micro USB port and stick an iPhone magnetic adapter in its place.

I took apart one of those magnetic Lightning adapters and, while it requires some soldering skills, it is not impossible to find and connect wires to GND, Vcc, D+, and D- traces. Data is not exposed on pads by the way. You have to peel off the shell to get to them.

But soldering to power is easy - you just cover all other contacts with kapton tape before soldering.

Hey, I was also involved in this project and just wanted to jump in. Like @Xenon27 said, our port was pretty much entirely dead, which ruled out a magnetic port. Additionally, we did not have the time to order a magnetic cable before states, and wanted a quicker solution that allowed us to continue working. But really, that brings me to the main reason we did this.

I’m pretty sure it is, but again, we needed a functional controller before states, and our program has a shortage of controllers with working ports. Additionally, the smart port is really convenient for us even compared to when we had new ports or magnetic cables. Using it doesn’t wear the port down (which magnetic cables slow down but don’t entirely stop), and the fact that it clicks in and just works has made prototyping our auton much more convenient.

This was also the oldest controller in the program, so we were prepared to absorb the cost of replacement.


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