FRC 95 The Grasshoppers 2020 Build Thread

Disclaimer: not a programmer

Do you need a brake out board for talons to use encoders? Can you use the spark max breakout board on talons?

Strictly speaking, no. Depending on the encoder, you could put together your own harness without a board, but they do make it easier. I think, though I’m basing this off a guess and photos, that you could connect an encoder to a talon using a sparkmax breakout. You’d just have to do your due diligence to make sure you’re getting the right wires on the right pads, because the pinouts are subtly different so the labels may or may not be correct.

To hopefully explain this a little better, the spark max and talon data ports use the same pinout, but also they don’t.

When in brushed motor mode, they’re the same.

When running a brush-less motor, the encoder A+B pins in the data port are shared with the pins in the encoder port used by the neos built in encoder, and only one encoder can be connected to those pins at a time (Edit: and the neo encoder has to be connected in order for it to work). Rev thought of this and helpfully includes an option for an ‘alternate encoder’ mode that reassigns pins in the data port for a second encoder. Those are pins 6 and 8, which in CRTE’s implementation are not connected and the Reverse limit switch, respectively.

This means that you can’t use the CTRE breakout boards to connect another encoder to the sparkmaxs because those boards don’t breakout pin 6. Rev does sell a breakout that includes pin 6 and is labeled correctly for the sparkmax.

That’s really interesting, thank you for this! To confirm: you could use the REV one on a talon but you can’t use the CTRE on on a spark connected to a NEO?

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Piggy backing off of this, what are the benefits of using a breakout board over plugging up straight to the talon (or rio)?

If you use the BOB you can connect any encoder you want within reason (we love the Grayhill 63R-256) to the Talon/Spark MAX internal control loop. This control loop runs at 1kHz, which is a lot faster than the Athena, and saves the computational power of the Athena for other things. Plus you can put the controller next to the motor and not run encoders wires all over the place.

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I think that is the case. Just to be clear, I don’t work for either Rev or CTRE, so plug things into your expensive speed controllers at your own risk.

It probably won’t break anything. It appears that the rev breakout board breaks out all 10 pins, so with a bit of work on your part it should be easy to map them to the Talons data port.

Since they cost about the same and they both appear to be in stock, I’d suggest using the ‘correct’ board for the speed controller, but hey, I ain’t the boss of you.



What are the advantages of breakout boards? For spark maxes, it allows you to use an external encoder with neos. But what about for talons?

Same benefits for both.
-Less wiring in some cases
-Faster/smoother control loops
-Encoder flexibility
-Less computational burden on Athena

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Are you not able to plug the encoder directly into the talon? (Sorry if this is a stupid question) we are planning on using the rev through bore encoders if that gives you more information.

I am not entirely sure. @Greg_Needel can you provide your expert advice please?

If it is a srx mag encoder, or has a similarly compatible wiring harness, yes you may. If it’s a different encoder, like the greyhill encoders we like, you’d need to splice the ribbon cable that connects to the talon into whatever wiring harness connects to the encoder, and the breakout makes that a lot easier. Page 19 of the talon SRX has a wiring diagram. So far as I can tell, the pins are 5v compatible (the exception being the analog input, which is 3.3v).

The rev through bore encoder appears to use the 6 pin ‘encoder’ port on the spark max, with the option of a wiring harness that breaks that out into a few other connectors. You’d have to check wtih Rev and/or ctre to see what your options are for connecting to a Talon, but it’ll probably include a breakout board. .

Thanks for the help, but out of a courtesy to you, I asked my question in a separate thread so I won’t clutter your build thread with my questions. Here is the link to the thread if anyone is interested.


Don’t worry about leading me astray. Actually, we might have used the CTRE boards on the Spark port and severely messed up our stuff at some point had you not posted. We did just order more REV boards though so all good!

As a fellow lover of Greyhill 63Rs, it’s looking like we’re going to finally make the switch to trusting the NEO internal encoders this year. Despite being on the wrong side of our drivetrain backlash, our path following software seems to be handling the NEO encoders just fine. Not 100% locked into this decision, but it might be another option for you should you continue to have breakout issues.

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My best advice is design for both. We’re trying out the NEO encoders, but the drive gearboxes have mounting points for Greyhills on the correct side of the backlash, just in case.


We did the same. We are going to try to use the NEO encoders but have a location for mounting external encoders if that does not work well enough.

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@JamesCH95 We’ve designed and sent out some boards that convert the talon port to a CAT5 cable, then CAT5 to limit switch or back to that 10pin connector. We can send one your way if you want to give it a shot.


@droswell thanks for the offer! We will pass for now though. We are not planning on having any sensor runs that are very far at all.

Depressing update: two snow days in a row, yesterday and today, has been not great for progress.

Hopefully working Saturday and Sunday will catch us back up!