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- // ---------------------------------------------------------------------------
- // Calculate a ping median using the ping_timer() method.
- // ---------------------------------------------------------------------------
- #include <NewPing.h>
- #define ITERATIONS 5 // Number of iterations.
- #define TRIGGER_PIN 12 // Arduino pin tied to trigger pin on ping sensor.
- #define ECHO_PIN 11 // Arduino pin tied to echo pin on ping sensor.
- #define MAX_DISTANCE 200 // Maximum distance (in cm) to ping.
- #define PING_INTERVAL 33 // Milliseconds between sensor pings (29ms is about the min to avoid cross-sensor echo).
- unsigned long pingTimer[ITERATIONS]; // Holds the times when the next ping should happen for each iteration.
- unsigned int cm[ITERATIONS]; // Where the ping distances are stored.
- uint8_t currentIteration = 0; // Keeps track of iteration step.
- NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.
- void setup() {
- Serial.begin(115200);
- pingTimer[0] = millis() + 75; // First ping starts at 75ms, gives time for the Arduino to chill before starting.
- for (uint8_t i = 1; i < ITERATIONS; i++) // Set the starting time for each iteration.
- pingTimer[i] = pingTimer[i - 1] + PING_INTERVAL;
- }
- void loop() {
- for (uint8_t i = 0; i < ITERATIONS; i++) { // Loop through all the iterations.
- if (millis() >= pingTimer[i]) { // Is it this iteration's time to ping?
- pingTimer[i] += PING_INTERVAL * ITERATIONS; // Set next time this sensor will be pinged.
- if (i == 0 && currentIteration == ITERATIONS - 1) oneSensorCycle(); // Sensor ping cycle complete, do something with the results.
- sonar.timer_stop(); // Make sure previous timer is canceled before starting a new ping (insurance).
- currentIteration = i; // Sensor being accessed.
- cm[currentIteration] = 0; // Make distance zero in case there's no ping echo for this iteration.
- sonar.ping_timer(echoCheck); // Do the ping (processing continues, interrupt will call echoCheck to look for echo).
- }
- }
- // Other code that *DOESN'T* analyze ping results can go here.
- }
- void echoCheck() { // If ping received, set the sensor distance to array.
- if (sonar.check_timer())
- cm[currentIteration] = sonar.ping_result / US_ROUNDTRIP_CM;
- }
- void oneSensorCycle() { // All iterations complete, calculate the median.
- unsigned int uS[ITERATIONS];
- uint8_t j, it = ITERATIONS;
- uS[0] = NO_ECHO;
- for (uint8_t i = 0; i < it; i++) { // Loop through iteration results.
- if (cm[i] != NO_ECHO) { // Ping in range, include as part of median.
- if (i > 0) { // Don't start sort till second ping.
- for (j = i; j > 0 && uS[j - 1] < cm[i]; j--) // Insertion sort loop.
- uS[j] = uS[j - 1]; // Shift ping array to correct position for sort insertion.
- } else j = 0; // First ping is sort starting point.
- uS[j] = cm[i]; // Add last ping to array in sorted position.
- } else it--; // Ping out of range, skip and don't include as part of median.
- }
- Serial.print(uS[it >> 1]);
- Serial.println("cm");
- }
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