Noob Questions Please Answer

[roboticnoob11]

I'm interested in starting a robotics team/club at my school, and have nearly made the decision to go with vex. I've just need to find out a few more things (rather quickly because radioshack is running out) before I go ahead and buy the robots.

1) I've looked on the internet, and people seem to disagree about whether you can program in c with the normal programming kit (it would be nice to have the option of programming in c as well because I'm interested in programming the robots to be autonomous). So is it possible in any way to program in C with the normal programming kit?

2) Are vex robots compatible with r/c toy batteries if they are the appropriate voltage?

3) Honestly, are Vex robots a good choice if you are going to program them to be autonomous?

4) Are vex robots compatible with generic/3rd party sensors? Somwhere I read that someone had used a "custom" IR sensor.......

[bcieslak]

From my experience:
1) You need to buy the programming kit for the special cable. You can use MPLAB and the C18 compiler if your an old time C programmer and don't like the glitzy bells and whistles of EasyC. I personally don;t care for Easy C but thats because I've been programming for 20 years and old habits are hard to break. You will also need the IFI downloader. Yo can get that from the vex website along with sample code and the all important Default code.

2)I will defer this one to the VEXlabs guys since its their warranty at stake. The Vex power packs are so cheap at radio shack that it would be silly to miss the deal.

3)They are good robots to experiment with autonomously, especially if you master the programming and archietecture of the default code that is provided. You have access all the IO and PWMS. Programming info for the VEX is scarce. But check out the IFI website and look at the programming manuals for the FRC controller and the minicontroller (aslo called EDUbot). THe Vex program structure is 'almost' the same. I modeld some of our FRC autonomous stuff on the VEX.

4)Whatever you can hook up to digital IO and A/d's can be used on the VEX. Just watch the voltage levels and polarities. I have third party shaft encoders from DigiKey and IR range finders from Hobby Engineering on mine. You can even create smart sensors and talk over the additional serial port. I use the CMU camera.(its really more like a vision system) for example. The thing that makes VEX a pain is the connectors used to attach senors to the IO ports. I bought cables with the connectors on them and cut them to fit my needs. My vex starter kit comes with bumper switches and limit switches.

Last bit of advice...Read robot books...learn about interfacing sensors and behavioural programming.

My two cents worth.
Good Luck and have Fun.

[fryfrog]

1) From what I have seen, you can use the EasyC that comes with the kit or use MPLAB which is free... or something? I think the "new" kits from vexlabs will offer MPLAB.

2) I'm not an official vex labs person! The bot battery is a 7.2V NiCD (or NiMH) standard RC car battery. I bought 2 from a hobby store for like $10 each. The transmitter is a 9.6V NiCD / NiMH too, got them from radioshack. $10 for battery, $25 for batt + charger. The $40 (or $80?) they charge for a 9.6V, 7.2V and charger is... dumb-tarded.

In theory, the transmitter runs on 12V and the bot runs on 9V (when filled with 1.5V normal batteries), so you could *probably* run an 8.4V pack (7 cell instead of 6) for a bit of extra umpf. I don't think there are any 10 cell (12V) NiMH / NiCD packs that would fit in the transmitter.

3) I've been a big fan of robotics and building since Lego Mindstorms came out. Unfortunatly, I am not in any sort of school so it has always been a hobby. And I never got into the electronics kit, so maybe I'm not that great a fan.

IMHO, Lego Mindstorms (or the new NXT) make a great kit for younger crowds. Or perhaps for quicker building and less physically abusive use. It is a lot easier to snap together a robot than it is to screw it together. Lego also has a **** TON of parts available, both robot related and not.

But I like my Vex. I have 2 starter kits and tons of other items, I love it. I just wish I had some friends or kids that liked it too... I have 3 transmitters and no one to play with!

4) Haven't done anything with 3rd party sensors yet. I was kind of annoyed at the system used by Vex, as the connectors are of course the exact opposite of standard RC gear. Of course? :p

[artdutra04]

1) I've looked on the internet, and people seem to disagree about whether you can program in c with the normal programming kit (it would be nice to have the option of programming in c as well because I'm interested in programming the robots to be autonomous). So is it possible in any way to program in C with the normal programming kit?As long as you purchase the vex programming module, you can use either EasyC (visual GUI) or MPLAB IDE ('hard line coding'). If you use MPLAB, you will need the IFI Loader to download the code to the Vex robot.

2) Are vex robots compatible with r/c toy batteries if they are the appropriate voltage?Any 7.2v hobby r/c battery (with a standard r/c battery connector) will work with the Vex Controller.

3) Honestly, are Vex robots a good choice if you are going to program them to be autonomous?Vex is a great platform to combine the mechanical and programming aspects. Whereas there are plenty of Linux-based microcontrollers and similar platforms that offer a hardcore approach to autonomous progrogramming, the Vex controller is a "middle-ground" approach that has many advanced capabilities while still being user-friendly enough for 14 year old teenagers to use.

4) Are vex robots compatible with generic/3rd party sensors? Somwhere I read that someone had used a "custom" IR sensor.......That was probably me. ;)

Any 5v analog or digital device will work with Vex, but the key part there is the 5 volt. A 12v sensor will not work with Vex, as the power pins on the Controller only provide 5v. As long as its the right voltage, you can use custom IR short/long range, ultrasonic, limit switches, potentiometers, encoders, accelerometers, etc. with Vex.

[coinvoyager]

You do not need mplab to compile and run 'c' programs for vex. Everthing you need comes with the programming kit, including the loader. You can update your loader from the vex web site, but you don't have to. I posted on the technical forum how to do this here:

http://www.vexforum.com/showthread.php?p=327#post327

I downloaded the student edition of mplab and it appeared to me to be just an assembler. Maybe there is a development environment for "c" in there but I could not find it so I removed it.

The programming kit comes with Microchip's c18 compiler (http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en010014&part=SW006011)that compiles 'c' code for the vex microcontroller. Note that the easyC program is just a visual wrapper around this compiler. EasyC generates "c" code which it sends to Microchip's compiler which in turns produces a hex file. The hex file is then sent to your vex controller.

Note that Microchip does not fully support (or claim to support) ansi-c. I don't know what all of the caveats are yet but one tip is to always use braces with your conditionals (no one-statement shortcuts.) I observed some erratic behavior if you do not. This is likely documented somewhere and I have not looked very hard.

[artdutra04]

I downloaded the student edition of mplab and it appeared to me to be just an assembler. Maybe there is a development environment for "c" in there but I could not find it so I removed it.The MPLAB IDE (integrated development environment) is available to FIRST Robotics Competition (http://www.usfirst.org/) (FRC) teams in the yearly "Kit of Parts" that teams recieve when they register for a FRC Team. The parent organization of FRC - FIRST - is also the parent organization of the FIRST Vex Challenge (http://www.usfirst.org/vex/) (FVC) and the FIRST Lego League (http://www.usfirst.org/jrobtcs/flego.htm) (FLL). :)

[Malhon648]

the only problem with the batteries i've found is that the plug in on the robot is the 9.6 volt size, so the 7.2's ive seen have too small of a connector, but this can be changed on the battery pack

[fryfrog]

Er, the plug on the Vex Controller is identical to *all* Hobby / RC 7.2V battery packs. The "Vex" power kit is just an RC 7.2V battery.

The plug in the transmitter is the same kind as well, so no worries there.