The point of the Parking Assistant is to record and accurately relay to the driver the distance to the closest obstacle in front of his or her car. In addition, It gives the driver audible cues so that he or she may park without diverting his or her attention. To perform these tasks, we knew that the system had to be relatively accurate, and perform updates at a high enough rate to be useful.
The parking assistant utilizes two Atmel AT90S8515 microcontrollers connected via one-way radio link. One microcontroller is mounted to the front of the car in a protected area or even behind the grill. Connected to it are an ultrasonic ranger capable of measuring distances in the range of 3cm to 3m and an AM digital radio transmitter. This controller continually transmits ultrasonic pulses via the ranger and measures their return times.
Following each return pulse, the microcontroller calculates the distance to the obstacle based on a fixed formula. It then transmits each distance using the attached transmitter to the second Atmel MPU which is equipped with a matched receiver.
In addition to the receiver, the second MPU is connected to a miniature speaker and an LCD. The LCD displays the current distance in centimeters, while the speaker emits short pulses with a period that varies directly with distance.
Three additional features are available through 3 of the pushbuttons available on the STK200. Button 7 calibrates the distance to 0 every time it is pressed, button 6 resets the receiver to report absolute distance, and button 4 toggles the speaker on and off, in case it becomes an annoyance to the driver.
To learn yet MORE about the Parking Assistance, please proceed to the Program/Hardware Design portion of the site.