Oh hello there! I'm pretty new with robotics and all of that exciting stuff. I'd been wanting a microcontroller for a few years, and when mbed gave out free mbeds, (yay) I got one and messed around with it a bit.
I got a Parallax PING sensor a couple weeks ago, and have finally gotten around to trying to use it. Here's my problem: The sensor blinks when I send it a signal, but it doesn't send anything back. The sensor is rated for 5 volts, and I've gotten it to work with both 4.5v and 6v. (6v was only for testing, I'm not planning on using it with 6v all the time.)
My exact C++ code is the following: (hopefully you'll be able to make out what it does, it's pretty heavily commented. It's code copied straight from the mbed site. I did make a few debugging changes, but those shouldn't affect it too much.)
#include "mbed.h"
DigitalInOut pingPin(p10); //sets ping pin to pin 10 (digital in and out)
DigitalOut ld1(LED1); //sets "ld1" as the built-in LED1
DigitalOut ld2(LED2);
Timer tmr; //creates a timer
long microsecondsToInches(long microseconds);
long microsecondsToCentimeters(long microseconds);
int main() {
while (1) {
// establish variables for duration of the ping,
// and the distance result in inches and centimeters:
long duration, inches, cm;
// The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
pingPin.output();//set ping pin to output
pingPin = 0;
wait_us(2);
pingPin = 1;
wait_us(5);
pingPin = 0;
ld1=1;
// The same pin is used to read the signal from the PING))): a HIGH
// pulse whose duration is the time (in microseconds) from the sending
// of the ping to the reception of its echo off of an object.
pingPin.input();
while (!pingPin); // wait for high
tmr.start();
while (pingPin); // wait for low
duration = tmr.read_us();
ld2=1;
// convert the time into a distance
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);
wait_ms(100);
}
}
long microsecondsToInches(long microseconds) {
// According to Parallax's datasheet for the PING))), there are
// 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
// second). This gives the distance travelled by the ping, outbound
// and return, so we divide by 2 to get the distance of the obstacle.
// See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
return microseconds / 74 / 2;
}
long microsecondsToCentimeters(long microseconds) {
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.
return microseconds / 29 / 2;
}
I appreciate the help, and if I haven't been very clear, just ask for more details.