Those pesky mice...
 

This year knowing where you are would be muy importante. Thus, our team has kind of decided to use optical mice, two of them, to determine position and direction. After doing some searching I have cleared up some of my questions but I still have two:

1) Does anyone have a brand they might recommend and a way to (semi) easily wire both mice to the Robot Controller? (e.g. a converter)

2) If not, with a recommended brand could you include specs on the wires so I could (hopefully) do it myself?

Thanks.

Re: Those pesky mice...
 

The Chiklet is the only legal way to do a USB conversion to the controller ports. It does need its own power, though.

Barring that, you would need to wire your own connection.

Re: Those pesky mice...
 

I think he means to mount the mice on the robot; in such a case the chiklet/etc restrictions would not apply.

I can't help with the mouse interface though. But, do keep in mind that it is essentially dead reckoning, so errors are cumulative and significant (meaning important).

Don

Re: Those pesky mice...
 

Yes, that is what I mean. I realize we cannot use the chicklet, though. However, by searching these forums I get the distinct impression teams from past years have managed to do what we plan to do. Looking at diagrams is helping me some but to anyone with experience doing this... Please help!

Re: Those pesky mice...
 

Using mice is what robot enthusiasts have tried in the SRS robotic groups. I have heard of one person doing that with small robots. My concern for these fast moving robots is that you would go faster than the mice could record and keep up with.

Re: Those pesky mice...
 

That's where the whole "we kind of decided it" comes into play... Really it was me and an engineering mentor. Our head and secondary engineers are currently gone on a scout camp out, so I haven't talked to them about our maximum speed. But really, I've got to start pursuing this now because if it does work it'll be great and if it doesn't I've got to learn how to use the quad optical encoders and gyroscope in unison...

Speaking of which, I've found a diagram I can use to wire a USB optical mouse myself. Unfortunately, I need to know what D+ and D- correspond to. I'm guessing one means data in and the other data out, but which way? (As in does D+ mean data going into the mouse or into the microcontroller?) Here's the diagram, courtesy of Wikipedia.

Re: Those pesky mice...
 

No, USB uses two wires for data, so they are both carrying the same signals exactly, except one is inverted from the other. Google "Differential Signaling"

Re: Those pesky mice...
 

...
Ah.
Because I so would've got that if left to my own devices, because of course that makes sense that D+ and D- would mean Differential Signaling.
...
That's why I stick to computers. And because I would've never been able to find that out on my own, Arigato, Don Rotolo.

Next question...

Is there any way to do the whole Differential Signaling before going to the RC? Because if I do my math correctly, 3 pins do not equal 4 wires.

Re: Those pesky mice...
 

Your definitly up for a challenge, if you want to use a USB mouse as a position sensor.

You are going to most definitly need an external co-processor, with a USB host chip, and appropriate firmware to decode the HID stream from the mouse to something the RC can understand, like a simple TTL serial stream.

If you can get a hold of some ps/2 mice, it can make your job MUCH easier, and you can easily decode ps/2.

Good luck!

Re: Those pesky mice...
 

I agree: USB is not as simple as connecting it to the robot controller and decoding data. There is a LOT more in there...

I suggest some web searches, see if anyone else has done it.

Don

Re: Those pesky mice...
 

Some mice use an Avago optical mouse controller chip and a Cypress microcontroler. On these mice you can by pass the micro controller and interface with the chip by SPI. That part will work. The problem is with the optics. Others have tried with custom optics. I don't think any one had success with FRC scale and carpet.

Re: Those pesky mice...
 

I attempted this several years ago on a simple robotics project unrelated to FIRST. I ran into several problems.
The mouse must see texture as it compares one image to the next to determine motion and direction. Good imaging is important so before you spend a lot of time make sure the official carpet is not of a nature that treads, dirt or other debris might get caught in the optics as the mouse moves along the floor.
Another test is with the optical mouse you plan to use. There are many makers out there. You may want to plug it into a computer, use a mouse pad, and check repeatability. In other words. pick a spot on the mouse pad. look at the location of the pointer on the screen, move the mouse away and them back to the start point and see what kind of error you get on the screen. This will help you determine max speed your robot can go with that particular mouse.
This doesn't directly address what you are doing but it's an interesting hack and might help.
http://www.contrib.andrew.cmu.edu/~t...ision_Project/
I DID see a small robot that used a mouse for guidance, but that was on a smooth, hard floor with texturing. Parts of the floor I tried to transverse were too smooth for the mouse to pick up the motion and thought it was standing still.

Good luck

Steve

Re: Those pesky mice...
 

is it possible to use a mouse with the usb chicklet on the OI? i have no idea since I have never used one of the chicklets, but if it is, then you could attach a 15pin connector to the chicklet and solder cut-off PWM cables to the other side of it and attach to the robot controller. it all hinges on if the chicklet can recognize the mouse and work with it then. it says in the .pdf file for the chicklet that it can use a "microsoft inteligent optical mouse" so then, you could make a modification of a backup battery recharge circuit for powering the chicklet and have it all be a custom circuit.

well, so far in my head I have come up with a way to do it. so, it would be just like rigging up a custom OI box, but attaching to the robot instead. use the pinout guide on IFI's website to help you find which pins should be connected to the analog connectors of the robot controller, and which should be connected to the digital pins.

note: I have no experience with using optical mice with the robot or with the chicklet, but I know that if the chicklet is supposed to emulate a joystick, then it can produce the same signal as the stuff in the joystick, which also happens to be the same stuff intended to connect to the robot controller, namely 10k ohm potentiometers.

Re: Those pesky mice...
 

Why not? It's legal, and it will do all the trouble of decoding the USB protocol into analog voltages for the two axes. Then all you need is an adapter to go from gameport to three-pin headers, which is pretty much a ten-minute strip-and-solder job. You may have to buy the specific mouse that the Chicklet supports, but that is by far the easiest way to approach the interface problem... much better than trying to bit-bang.

Re: Those pesky mice...
 

They're trying to use the mice as position sensors on the robot, not as driving tools on the OI.

Re: Those pesky mice...
 

I know that. That's why I'm describing the process of adapting the Chicklet to mate with the three-pin headers on the RC.

Re: Those pesky mice...
 

Ah, OK. The fun begins...Now, how do you power the Chicklet on the robot? Direct connection to the 7.2V battery, or will a three-pin header tranmit enough power?

Re: Those pesky mice...
 

The Chicklet claims to draw no more than 500mA. The camera had no trouble with drawing 235mA from the PWM headers... I'm no EE, but I'd expect that the Chicklet would be okay, too.

Re: Those pesky mice...
 

Well, thanks for your help guys. Actually, if I were doing the mouse idea I would just take a ps/2 mouse and strip it down to D+, +, and -. Then I'd plug that directly in the RC. But, as it turns out, I can't seem to find mice that operate faster than around 20 inches/second. Since our robot will be going feet/second, the mouse wouldn't be able to keep up. There's also not enough room on the bottom to mount it higher and widen its camera angle nor can we do that with the ceiling on account of the rack. So it looks like I'm stuck with a gyro, accelerometer, and gear tooth/optical encoder combo using a line sensor for recalibration with the alliance lines.