The HexCrawler for a Science project

lassethomsen

Hi-
I've been lurking around in the forums, but dosnt have found answers to all my questions. So here I go.

For a science project (bachelor) we want to make some software to controll a robot. The HexCrawler seems like a very good platform to use. (Also to expand on, later in our studies)

In the kit there is a BS2 microcrontroller as i read it, but can you do som real world programming on those? Ive tried the ATMEL Mega16 and its a fine controller and you can write it in c, but i dont really know much about this BS2 controller. Can anybody tell me if its realistict to do som serious programming in the BASIC language, or is it just more a prototyping language? Or perhaps even better, can you mount another crontroller to the HexaCrawler? (and a little bit easy, im a software dude).

Our plan is in rough draft this:

Control a mobilerobot, obstangle avoid etc the basic controll.
The robot should some how (part of the project) could load a map, and should follow a route. So there is a need for a compas.
Video link and controll with some posibility to make feedback to a central.

Besides the videolink stuff.
Is it possible to make this project from what there is in the HexCrawler kit, or do i need something extra?

Sorry for any allready asked questions, but i just havnt been able to find the answers in the forum.

Best Regards
Lasse Thomsen

Chris Savage

Hello,

·· Bear in mind that, while the Hex crawler comes with a BS2 which is more than capable of controlling it and several sensors, we have other controllers available which could be used and that are more powerful, such as the SX and the Propeller.· I hope this helps.· Take care.

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Chris Savage
Parallax Tech Support

Mike Green

The HexCrawler is really just a mobile platform with a simple controller. It is an excellent building block for the kind of project you're interested in. It doesn't include any sensory devices. It's designed for mounting all kinds of devices. The PING ultrasonic distance sensor mounted on its optional servo bracket is a good beginning. Parallax recently posted a video showing the BOE-BOT with a PING sensor on this bracket scanning a table top with two metal cylinders, then moving directly to the closest cylinder. The same kind of thing can be done with the HexCrawler. There is a Hitachi compass module that can be mounted to the same bracket as the PING to provide absolute references for the PING sensor when mapping the environment.

You could mount a video camera and transmitter on the HexCrawler. Most of them are made for security monitoring purposes and are not designed for battery operation. Some of the R/C (radio controlled) model airplane suppliers have much better systems from a size/weight/power standpoint.

The BS2 controller that comes with the BOE-BOT and HexCrawler is fairly limited in program memory space and has quite limited data storage. Consider replacing the BS2 with a BS2p which has more program space which can also be used for storing a map and has additional data storage. Also investigate using the Propeller. It's much much faster than any of the Stamps, has more memory, and can function more independently than the Stamps. The Propeller Demo Board can attach to a keyboard, mouse, VGA or video display. Disadvantages of the Propeller is that it's new. There's not much documentation yet while there are several books on programming and on robotics and industrial/process control using the Stamp. There are plenty of examples of the use of a variety of sensors with the Stamp while there are only a few examples using the Propeller.

lassethomsen

Hi thanks for your replies.

So if i purchase a HexCrawler I would also have to add a Ping ultrasonic sensor, a compass and perhaps replace the onboard controller with a more powerfull one like the propeller.

A question about the Propeller, I have been working with the Atmel MEGA16, and for this chip can I write my software in C (which i love), but as i see it, you have to write Assembley for the Propeller, is this true? Not that i see Assembley as something bad, I just like to have a little higher lever of programming langauge.

About the documentation, as long as Parallax has made a full release of registers, use of it, etc,etc,etc, it shouldnt be any trouble.

But in my search around on the www, it sure looks like that the hexcrawler is the platform im going to use. (Maybe the Quad version if, the collected price becomes to high)

Mike Green

The Propeller has two languages. Assembly language is one of them. The other is an interpreted (but very fast) high level language called SPIN. It has some features like C, some object programming, and the assembler is part of the SPIN compiler. You can write routines in SPIN to do serial I/O "bit banging" or for controlling up to 4 servos at a time, but, for higher performance, you have to run more than one SPIN interpreter (trivial to do .. takes one statement) or use an assembly routine. There's an expanding library of SPIN/assembly "objects" including one that does VGA graphics, one that does VGA text up to 1024x768 resolution, one that can control up to 32 servos at a time, a PS/2 keyboard interface, a PS/2 mouse interface, and a complete IEEE floating point package. There's a Propeller manual that's a free download (or buy the paper version) that has a complete description of the chip, the IDE (integrated development environment), the SPIN language, and the complete assembly instruction set.

lassethomsen

For our project we have now made a list of the following we need.

HexCrawler Kit
Proppeller kit.
Compas module.
Accelorometer.
Sonic Ping for object detection.
The mounting bracket for the sonic ping.

And it sould not be any trouble to attach the proppeller demo board to the robot?

We are also gonna need some sort of a power-source. Any ideas or suggestions?
Instead of using a videolink, we are considering to build a robot which can find a rfid chip i a room, and signal back to basestation when found, and the maybe return home.
So to do this we need:

RFID reader
The radio reciever and transmitter and a couple of rfid chips.

Are we missing anything or is this what we need? (if you include a powersource)

Kevin Wood

For your Propeller, you might want to check out the Propeller Robotics Controller Kit: www.wulfden.org/PRC/

lassethomsen

Att: Mike W.
Thanks for your link, I will take a closer look at this later. But it sure look like the connection between the HexCrawler and the Proppeller that I have been looking for.
But Is there anything in my list, I should add / remove?

Mike Green

You will need a power source (6 cell NiMH battery pack and charger), cables, mechanical hardware (screws, nuts, washers, etc.)
For the battery pack, a 7.2V Radio Control NiMH battery pack is more readily available and often comes with (or can be purchased with) a rapid charger. I suggest keeping both the Stamp and the Propeller mounted on the robot chassis. You can learn more easily about the robot and how to control it using the Stamp and the existing books in the Parallax library. When you're ready to move the control functions over to the Propeller, they should be readily converted. The PING and compass already have "objects" in the Parallax Object Exchange that you can download and just use. There may be one for the accelerometer as well (I haven't looked). The servo controller just uses serial commands and there are several different serial drivers for the Propeller. In addition, if you use the Propeller Demo Board, you can temporarily attach a PS/2 keyboard and video monitor to help with debugging.

Consider using a ZigBee RF network adapter that Martin Hebel sells <http://www.selmaware.com/>, one for the robot and one for your PC.

lassethomsen

Hi thanks for all your replies. We are pretty close on purchasing the hardware (trought a Dutch dealer, its WAY to expensive to purchase from outside EU, if anyone can recommend a european dealer please let me know).

Just one last question or more a reasurance.

The Propeller Tool Software v 1.0 (Supports Win2K and above) is all that we need to compile software for the propeller chip? There is no limitations in anyway?

Best Regards.
Lasse Stig Thomsen.

John R.

The only limitations are those in your own mind...

Yes, the free software is all you need (on the PC end), and it is not limited in any way (time nor function).

You'll also need a means of connecting to the Propeller, but should be included in the "Propeller Kit" you had on your list.

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John R.

8 + 8 = 10

lassethomsen

Hi.

The Propeller on the demoboard has all stuff drawn out to VGA, Audio, etc. And only 8 pins for custom I/O. Is this enough to control the servo's and some sensors?

Mike Green

Each servo requires only one pin. Some sensors, like the PING, require only one pin. If you are not using the mouse, you can use those two pins for general I/O. If you are only using the TV output for debugging and control, you can use the 8 VGA outputs for control. There's a little crosstalk between some of the pins because of the VGA resistors, but that shouldn't be a problem if you're using the pins for controlling servos.

The main difficulty is in making the connections. You could certainly get 5 outputs using the VGA connector and parallelling those I/O pins with resistors connected together (1 each red, blue, green, H-sync, V-sync). If you're really good at soldering to SMT devices, you could attach fine wires to the LEDs to get access to both I/O pins of each color output pair to get another 3 output pins. It is easier to use a PropStick or WulfDen's Propeller Robot Controller, but, if you have a demo board, you can use some of the other I/O pins.

Post Edited (Mike Green) : 11/1/2006 2:56:03 PM GMT

lassethomsen

We did just in time realise this problem so instead we have ordered the PropStick, wich do looks a lot more like what we will need.

Thanks for you help.

So now all we can do is wait for the gear to arrive. [noparse]:)[/noparse]