Create ultrasonic.c

[moranod3]

Code works for a single sensor, the code for the second sensor is still buggy. The timer for the second sensor does not count at the correct speed and still needs to be fixed. Changes made to ultrasonic.h since the Ultrasonic_Init function does not pass filter_t, or the callback into the function in the working code.

[muhlbaier]

This is too processor specific to be acceptable. There should be a hal_ultrasonic.c or similar to implement the processor specific code. You don't need to support more than one processor but the module needs to be portable otherwise it isn't a module it is just a chunk of application specific code.

[moranod3]

What exactly is processor specific, because I know when we presented this you told us the hal_ultrasonic file we had was unnecessary. I'm assuming its the code in the Timer and Port interrupts but not 100% sure.