Xbox Joystick Design: Read Up and Down Directions on Motorola HC12 Eval Board

[frogdogbb]

Hello all been a while since I logged on, anyway I am trying to develop a product which uses an analog joystick. It needs to be small and thumb operated so I thought I would first design with a spare analog original xbox controller. I found that the resistance of the pot for the vertical direction when at center is approx. 4k ohm when pushed one way it goes to about 2.5k and when pushed the other way goes to 1.2K or close to that. My question is this, I would like to hook it up to a Motorola HC12 eval board I have but how to read this diference of up and down. I will sense the voltage but if both up and down directions produce voltages/resistances in the same direction how does one differentiate up from down?
Thanks

 

[berkeman]

It must be more than a 2-wire interface. How many wires are there? Can you see how it physically works inside (like see the two pots)?

 

[frogdogbb]

here are some shots of the board I drew a couple of arrows which is where the pots are sitting.

[img=http://img167.imagevenue.com/loc458/th_92178_S4300003_122_458lo.JPG]

[img=http://img169.imagevenue.com/loc554/th_92180_S4300005_122_554lo.JPG]

 

[NoTime]

Pic isn't any help.

You a probably hooking to the wrong pins or something else is going on.
Normally you would get a high resistance value in one extreme and a low resistance value in the other extreme.
All intermediate positions would have a resistance between the two extremes.

 

[frogdogbb]

That is exactly what I expected to see, hence the confusion the 3 solder points below each corresponding pot are where I have tested the ones that have the arrows drawn in the pic

 

[frogdogbb]

Maybe this will help I turned the unit on and tested the voltage across the pins from the potentiometers. I am still confused how this works though as in one position across the pins it goes one way and by switching one of the leads to the other pin it is opposite. See the drawing
oh click on it once brought up if it is out of focus

<< URL deleted by berkeman >>

 

[berkeman]

Maybe this will help I turned the unit on and tested the voltage across the pins from the potentiometers. I am still confused how this works though as in one position across the pins it goes one way and by switching one of the leads to the other pin it is opposite. See the drawing
oh click on it once brought up if it is out of focus

<< URL deleted by berkeman >>

Well, when I clicked on your link, I got to a Free Porn website. I think I'll delete your link for now. Don't do that again, frogdogbb.

 

[frogdogbb]

Sorry I did not do it must have been the piece of crap free image hosting guess I won't use that one anymore. I checked the post and clicked on the image to makesure it worked and it did so... How about this:

[img=http://img407.imageshack.us/img407/582/positionbl9.th.jpg]

 

[Averagesupernova]

The voltages you come up with make perfect sense. One end lead is the negative side of the 5 volt power supply and the other is the positive side. The center lead varies its resistance between the two. Naturally when the full supply voltage is between the center lead and one of the end leads, there will be no voltage between the center lead and the other end lead.

 

[frogdogbb]

I guess so, I got hung up because when I tested the resistance of the thing it was funky so I guess if I put +5V on one axis and -5V on the other axis it should be farily easy to come up with a program for it.
Thanks

 

[berkeman]

Sorry I did not do it must have been the piece of crap free image hosting guess I won't use that one anymore. I checked the post and clicked on the image to makesure it worked and it did so... How about this:

[img=http://img407.imageshack.us/img407/582/positionbl9.th.jpg]

Ah, that works much better. Yeah, I didn't think you did it on purpose. Just the image posting service as you said. Kinda' embarrasing for me at my desk at work though

Glad that you and supernova got it figured out.

 

[frogdogbb]

How about this, I have changed my original design to make this interface wireless. I am trying to figure out a way to transmit this joystick position without having a adc on the t/x side this is not possible is it? So I need a small chip/chips with t/x and dac additional processing can be done on the r/x. High resolution is not that important but size and power consumption is. I have found a number of chips but I is hard for a novice to figure out what a good method is for this. Does anyone with wireless experience have any suggestions or know of any chips.
Thanks

 

[berkeman]

You could use a couple voltage-to-frequency converters with audio frequency outputs, and then use a couple of cheap FM radio transmitters (you can buy cheap kits) that you tune to two different frequencies. Then you can use inexpensive FM receivers to pick up the two audio tones and then do your processing. Use a simple calibration routine (like is done on PCs with cheap joysticks) to help you figure out the center frequencies and extent frequencies for both axes.

 

[frogdogbb]

Thanks Berk i will check into that great idea

 

[frogdogbb]

Check out this bad boy

http://www.nvlsi.no/index.cfm?obj=product&act=display&pro=79

anybody have any experience with this chip? It looks like it has everything I need all in a convient package and small which is extremely important for this design. The only problem is a devolpment kit is $419 I need a grant or something anybody know where students can get grants for projects such as these?
Thanks

 

[berkeman]

Interesting. I hadn't thought of it before, but Cypress has something similar in their Wireless USB line of RF transceivers (WUSB). They also use the 2.4GHz ISM band, and their chips are targeted at wireless keyboards and mice. If you had a wireless keyboard setup on your PC using the WUSB technology, you could probably take apart the WUSB mouse and convert it into a joystick. I think WUSB peripherals are pretty reasonable in terms of cost, but I've never bought any.

Or even any wireless mouse -- maybe they just use a USB stick for the receiver?

http://www.tigerdirect.com/applicat...asp?CatId=9&SRCCODE=WEBGOOINPUT&CMP=KNC-GOOGL

 

[stymie222]

Joystick components

I have been unable to find answers on Joysticks elsewhere. Perhaps you people could help. I noticed while playing combat flight sims that some joysticks of the opposing players have the ability to turn tighter and faster than I can.{please disregard player ability, it is not the case here} Do the electronic components that are used in the contruction of the different sticks have different reaction/response times than others? Could better substitute electronic parts improve performance or communication with the game control assignments within the game? Are there any modifications, software / hardware accelerators that could be used to improve control functions?

 

[berkeman]

I don't know about comparative performces, but at least you should be sure to re-calibrate your joystick occasionally. The calibration routine should be in one of the control panels, depending on what your hardware and software are.