Vex Legal Speaker

It’s been mentioned a few times around the forum how V5 no longer has speaker support, as the required hardware is missing and it is impossible to produce audio without it.

Recently, I wanted to get some experience with circuit design, and I thought that designing a legal speaker would be an interesting project. This meant that the entire system had to be analog, as microcontrollers are explicitly forbidden, even in decorations, which made it different than most things I’ve worked on.

After some time, I finished this design, and am now able to use two ADI ports to create any tone from 0-4kHz. This is still limited, but it allows me to play basic music.
This would certainly not be allowed for user feedback, but I do personally think it would be legal as long as it stays non-functional. Unfortunately, it’s too late to ask the GDC, but I’ve talked to a Worlds head ref who doesn’t think there should be any major issues.

Here’s a video of it working:–Y. You can also access part of my team’s notebook documenting its design process here if anyone is interested


That is a fantastic project!

I suspect you would even be able to use it for DRIVER feedback. If you look at <R12>:


from your documentation.

Our findings showed that it was quite limited in function, as it didn’t do exactly what the documentation claimed. Rather than output 0-5V as a PWM signal, it outputted a quite limited duty cycle with ranging only from ~6% to 13% of a 3.3V 60hz signal,

I’m not sure we ever claimed anything else. This is a standard servo pwm signal.


I’m well aware, it was more of a comment on the pros documentation, which claimed a 0-5V 12-bit output. In reality, it’s only an 8-bit hobby servo signal, with a 3.3V peak. I obviously ended up dealing with it, it just wasn’t exactly what I expected. I think I’ll open a pull request with them to fix it, there wasn’t anything wrong on your end.


You’re correct in that it wouldn’t violate <R12.f> in that it doesn’t provide robot feedback, but it would break <R12.g>, as it isn’t providing visual feedback, but rather audible. While the intent of the rule may have been to allow any feedback to drive team members, my device wouldn’t fall under the rule as it is written. The only real way to tell is to talk to the GDC, which I guess I could try at worlds. We’ll see.


Good catch.

Hopefully, GDC will find that this falls under <G3> (Use common sense).

I suspect the reason they specified visual feedback is that they did not want any form of electronic feedback and did not envision teams successfully designing an audio feedback system.

Based on the effort you spent implementing audio feedback, that was not an unreasonable assumption…


Actually, audio feedback diminishes access to those with hearing challenges in terms of feedback. For those who are visually challenged, the haptic feedback is an affordance.


This topic was automatically closed 365 days after the last reply. New replies are no longer allowed.