Robotics Assignment 5

In the following code we implemented the code for the sonar ranger. For this particular example we use a cricket to send a signal on the bus to this logochip to start the sonar sequence. Once the logochip receives a hexadecimal 180 it then goes off and starts the ranger. The way the ranger works, is that it needs a 5v pulse to start the sonar and it will return on its output pin the edge of the sonar pulse. The pulse represents the time it takes to send out a sonar signal and receive a response. To measure that time, the logochip timer gets started when we reach the edge of the pulse, and it gets stoped when we reach the oposite edge. The problem with this is that the resolution of the logochip timer is 1millisecond making the sonar computation a little off. We then use the knowledge that the speed of sound travels at approximatly 1inch every 74 microseconds to compute our result. The result then gets send on the bus to the cricket on the other end.

In the following code we implemented the bus/motor code for the Handy Cricket. This works by sending the command (hexidecimal 180) to the logochip on the cricket bus, and waiting for a response from the logochip. The logochip sends a 1 byte response to the cricket which represents the distance to the object imeadiatly in front of the sonar in inches. The cricket then takes that answer, and if the distance is greater than 7 inches it moves the motors forward for 1 millisecond then tries again. If the distance is less than 7 inches, the motors get turned to reverse for 1 millisecond. When the distance equals 7 inches, the motor is stopped.