Smart Ports Power Wire

This is mainly aimed for @jpearman.
Is there any way to provide power to a DC device through a smart port by taking a smart cable and splicing up one end? I’m trying to find a way to power LED lights from smart ports so that I don’t have to waste a legacy port.

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I’m not going to provide any pinout details, I know somewhere someone had posted that before, but yes, you will find one pin will have battery voltage (so anywhere from perhaps 11V to 14.4V) available, there will also be a GND (0V) pin. That voltage is higher than most LED strips would usually want, also much higher than the 5V available on the legacy ports, so check the specs carefully of whatever you try and connect it to. I also can’t say if using a smart port for anything other than a motor (or vision sensor etc.) would be competition legal.


Would I be able to turn the power on and off in the code with a setup like that?

Here is a pinout of the smart ports:


They use UART over RS-485, which is a half-duplex serial link with two data pins (A and B). The power pins (+ and -) are connected directly to the V5 battery lines, so as James said they are much higher voltage than you probably want (somewhere in the range of 13 V). Also, they cannot be switched on or off. To reasonably control one or more LEDs from a smart port, you’d need some custom electronics to interpret commands sent over the RS-485 link.

The only way to directly connect an LED to the V5 and be able to control it is via any of the 8 “legacy” ports (A through H). I also cannot comment on the exact legalities of using such a custom device in competition (I’m more familiar with the relevant rules for VEX U), but if you’re not sure after reviewing the game manual, I’d encourage you to open a Q&A question.


User programs cannot turn power for a smart port on and off. Depending on how the cable was made, the wire colors may be reversed from what is shown in the above photo.


I believe this year using an external power source for LEDs is now legal, so you do not have to waste any ports to power it. As per rule R12 (f):

Internal power sources (e.g. for a small blinking light) are permitted, provided that no other rules are violated and this source only provides power to the non-functional decoration (e.g. does not directly or indirectly influence any functional portions of the Robot).

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We are currently using 3-wire ports to power the lights. I custom-made some cables for it and I know it is legal.

could you show us how you made those custom cables?

That imagine doesn’t really help without the other half, here it is.



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