Hey everyone, I'm working on a sumo robot that uses four Ping sensors, the kind with 3 pins, to find targets. On previous attempts I could be lazy and use the pulseIn function- as found in the Ping example code- however this time around the team is using drill motors, which in terms of software behave identically to brushless. Because a lot of timing is required for motor control as well as other parts of the system, interrupts and delays (beyond a few micros) are out of the question- That includes pulseIn. Attempting to replace pulseIn with non-blocking code has been unsuccessful, generally resulting in the sensors firing but not returning data, or firing once and remaining off. So far as I can tell most of it boils down to:
-
Not understanding the return pulse of the ultrasonic sensor
-
Unsure of what pulseIn(pingPin, HIGH) is looking for and timing, several Arduino forum posts and the documentation differ on how it's triggered on/off
Thanks, much appreciated.
const int pingPin = 3;
unsigned long start = 0;
bool readingPulse = false;
int stage = 0;
void setup() {
// initialize serial communication:
Serial.begin(9600);
}
void loop() {
unsigned long duration, inches, cm;
if(stage == 0){
stage = 1;
digitalWrite(13, LOW);
pinMode(pingPin, OUTPUT);
digitalWrite(pingPin, LOW);
delayMicroseconds(2);
digitalWrite(pingPin, HIGH);
delayMicroseconds(5);
digitalWrite(pingPin, LOW);
pinMode(pingPin, INPUT);
}
//here's where pulseIn would be
if(stage == 1){
if(digitalRead(pingPin) == HIGH && readingPulse == false){
start = micros();
readingPulse = true;
digitalWrite(13, HIGH);
}
else if(digitalRead(pingPin) == LOW && readingPulse == true){
stage = 0;
duration = micros() - start;
readingPulse = false;
digitalWrite(13, LOW);
}
}
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);
Serial.print(inches);
Serial.print("in, ");
Serial.print(cm);
Serial.print("cm");
Serial.println();
}
long microsecondsToInches(long microseconds) {
return microseconds / 74 / 2;
}
long microsecondsToCentimeters(long microseconds) {
return microseconds / 29 / 2;
}
(Obviously this is a modified version of the Ping example code. Trying to minimize points of failure before getting too custom, since that code works fine with the sensors)
