Using Vex Brain as FRC Coprocessor

[Tom Bottiglieri]

Vex Controller: $150

Co-processor anyone? I'm sure you all know how to program for it!

[Richard Wallace]

Originally Posted by Tom Bottiglieri

Vex Controller: $150

Co-processor anyone? I'm sure you all know how to program for it!

IFI is a VENDOR => VEX Controller is a COTS electronic component => compliant(<R45>)=.TRUE.

$150 < $200 => compliant(<R49>)=.TRUE.

Don't know about compliance with <R51>. Can you run a VEX controller from a 12V battery? Specs say 7.2V, and draw is 62mA for the controller and receiver. Since the receiver can't be used, maybe the draw is a little less.

[lukevanoort]

Originally Posted by Richard

$150 < $200 => compliant(<R49>)=.TRUE.

Don't know about compliance with <R51>. Can you run a VEX controller from a 12V battery? Specs say 7.2V, and draw is 62mA for the controller and receiver. Since the receiver can't be used, maybe the draw is a little less.

Could you power it through the pwm outputs on the RC like the servos?

[Tom Bottiglieri]

Woah, my post got merged into a new thread. (I guess someone was expecting this topic to come up?)

Interfacing to the Vex controller shouldn't be hard at all. I haven't been able to play with my kit much since I bought it, but I have been able to interface the cmucam with the vex programming module and a male to male 9 pin serial cable. This setup could probably be become less bulky, as I'm pretty sure the only thing in the programming module box is an TTL->RSR232 converter chip like the one we get in the FRC kop.

Anyway, code to run this coproccesor shouldn't be hard at all. If theres enough support, and Mr. Watson permits me to use his serial driver (what a beautiful piece of software that is..), I should be able to get something released soon.

[UlTiMaTeP]

You need to build a 12v to 7.2 psu's which is fairly easy, the instructions are on IFI's white papers. Also nothing stops you from pulling a tap off of the backup battery supply.

[Richard Wallace]

Originally Posted by UlTiMaTeP

You need to build a 12v to 7.2 psu's which is fairly easy, the instructions are on IFI's white papers. Also nothing stops you from pulling a tap off of the backup battery supply.

Thanks for referencing the IFI white paper on powering the controller. [I think you mean this circuit which uses an LM317T regulator?]

Actually, as written for 2006, <R51> would stop you from pulling a tap off of the backup battery supply.

[UlTiMaTeP]

I was actually planning on building a few of these for purchase next season. It took me quite a long time to track down all the parts and most companies required me to spend 50$ min order.

[Rickertsen2]

Cheaper to build your own coprocessor

[Gdeaver]

Why do you need a coprocessor. Why would you want to spend 150$ just for a PIC coprocessor. What are you trying to do that the FRC can't handle. I could see a coprocessor if you wanted to use a sensor that was I2C or SPI. If you needed fast floating point math. If you wanted to play with machine vision. The Vex Modula would not be a good fit for these purposes. Either it's way to much $ or not powerful enough. There are several chip and carrier solutions on the market that would be easier and more cost effective.

[dlavery]

Originally Posted by Gdeaver

If you needed fast floating point math. If you wanted to play with machine vision.

Hmmmmm...

[Qbranch]

Originally Posted by Gdeaver

If you needed fast floating point math. If you wanted to play with machine vision.

Originally Posted by dlavery

Hmmmmm...

Machine vision is in the land of DSP processors... I don't think you could pull it off with a standard embedded processor... just capturing the pixels would probably take too long, let alone processing them. ( Taking too long to capture pixels = blurry image )

[DonRotolo]

Originally Posted by Richard

Thanks for referencing the IFI white paper on powering the controller. [I think you mean this circuit which uses an LM317T regulator?]

Actually, as written for 2006, <R51> would stop you from pulling a tap off of the backup battery supply.

I would not use that circuit to power a 7.2 volt Vex controller. You'd be far better off using the standard LM317T power circuit (like this), since the quoted circuit is designed to charge a 7.2 volt battery, not replace it. All of the parts are available from Radio Shack, or Jameco, DigiKey, Mouser, etc. You definitely need a heat sink, and it should be powered from a 12 volt tap off the fuse panel.

This is a good circuit to play with in the off season. The LM-317T is a very versatile circuit and everyone would be well-served to gain some familiarity with it - including it's disadvantages (such as heat generated and relative inefficiency with high voltage drops).

Don

[Qbranch]

My question is, why on earth do you need more processing power?

The PIC18F8722 processor runs at 40MHz, which is way faster and has way more flash than any of us could ever want. That is, of course, as long as you don't use any polling loops. (hopefully you aren't polling ). I'm running about 9 parallel processes this year, and no signs of lag...

The processor has 8 external interrupts and several internal interrupts along with four timers, four banks flash memory, 16 channels analog to digital converter, ...

Just curious does anyone had any ideas what they would do with a co processor if they had one?

-Q

[Donut]

Originally Posted by Qbranch

Just curious does anyone had any ideas what they would do with a co processor if they had one?

Originally I thought of a co processor to handle 6+ sonar sensors all requiring interrupts (because then we'd have no room for encoders). Since we've found ones that wouldn't require interrupts now though, I don't think we'd really have much use for it anymore.

If you had a sensor requiring a specific interface I could still see it.

[Gdeaver]

6 sonar sensors? What are you going to do about all the reflections from them ? 1 sonar and a couple Sharp IR's on servos would be better. What about if other robots have sonar? Yes there is a serial sonar on the market now and it has a narrow cone of detection. The problem with the FRC is that it wasn't designed with a communications bus for coprocs or multiple intelligent sensors. The spi and i2c are not available. If in the future the complexity of First robots gets to the point where coprocs are needed then The controller is going to need a major over haul. From what I've seen most teams barely tap the power of the controller we have now.