ros_arduino_firmware: ros_arduino_firmware: sensors.h Source File

00001 /* Functions for various sensor types */
00002 
00003 float microsecondsToCm(long microseconds)
00004 {
00005   // The speed of sound is 340 m/s or 29 microseconds per cm.
00006   // The ping travels out and back, so to find the distance of the
00007   // object we take half of the distance travelled.
00008   return microseconds / 29 / 2;
00009 }
00010 
00011 long Ping(int pin) {
00012   long duration, range;
00013 
00014   // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
00015   // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
00016   pinMode(pin, OUTPUT);
00017   digitalWrite(pin, LOW);
00018   delayMicroseconds(2);
00019   digitalWrite(pin, HIGH);
00020   delayMicroseconds(5);
00021   digitalWrite(pin, LOW);
00022 
00023   // The same pin is used to read the signal from the PING))): a HIGH
00024   // pulse whose duration is the time (in microseconds) from the sending
00025   // of the ping to the reception of its echo off of an object.
00026   pinMode(pin, INPUT);
00027   duration = pulseIn(pin, HIGH);
00028 
00029   // convert the time into meters
00030   range = microsecondsToCm(duration);
00031   
00032   return(range);
00033 }
00034