i was wondering if it is possible to use non-vex sensors to program with the the cortex microcontroller

Yes, it is possible to program for some non-VEX sensors. For analog sensors, you can configure the port as a potentiometer or light sensor. For simple digital sensors, a digital in can be used. For more advanced sensors that require communication, you might be able to use UART,I2C, or, if neither of those work, bit bang things out using digital in and out What sensors were you thinking about using in particular? Perhaps someone here can help you out.

thank you for the response, i was thinking of using the vex optical shaft encoder but there are some concerns with the autonomy with it. if the robot collide with another robot or object the sensor will lose its position and it wouldnt get accurate data. right now im looking at other sensors that could help me with the navigation during the autonomy section

If you are planning to use these components in a competition, I would take another look at the VEX Sack Attack Manual (found here), specifically sections <R5> to <R7>:



There may be exceptions to this, though, and I would suggest posting your question (with the specific parts you plan to use) in VEX's Q&A section for an official answer, as it is the only way to know for sure if a part is legal or not.

Yep, you can't use your own sensors in the competition unless you're in the college division.

i am in the college division. is there a way to program the ultrasonic sensor to only detect the signal that you emitted? if the opposition is also using an ultrasonic sensor, wouldnt it affects the the unwanted signals.

If your rangefinder is operating on the same frequency as that of the opposition's, then yes, the signals can interfere with each other. While there are ultrasoinics that operate at different frequencies, most on the market use 40 kHz. Unfortunately, I don't think that there is any easy way (past the calibration that is already done in the sensor) to differentiate between the echo from your ping, and the ping of another sensor *. What you can do however, is write a filter to weed out the erroneous values. It can be as simple as a low pass filter, or you can work up to something like a kalman filter. Take a look at the Wikipedia page on digital filters to lean more: http://en.wikipedia.org/wiki/Digital_filter

*It's possible to build your own sensor, and modulate a unique output signal over the ping, but that's probably a lot more trouble than it's worth. It would certainly be an interesting project though, and the necessary parts are available online if you with to try.

are there any sample code for the i2c port?

I know that this is a bit late, but did you think of using a laser sensor? http://www.pololu.com/catalog/product/136 or http://www.pololu.com/catalog/product/1132. This ultrasound uses 42KHz, https://www.sparkfun.com/products/9491.