added support for specifying the trigger length and waiting after tha…

…t before expecting the echo
d03n3rfr1tz3 · Jun 7, 2021 · 95e10a3 · 95e10a3
1 parent 92f4628
commit 95e10a3
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Showing 2 changed files with 12 additions and 4 deletions.
diff --git a/src/HCSR04.cpp b/src/HCSR04.cpp
@@ -9,13 +9,15 @@
 HCSR04Sensor::HCSR04Sensor() {}
 HCSR04Sensor::~HCSR04Sensor() { this->end(); }
 
-void HCSR04Sensor::begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, eUltraSonicUnlock_t unlock) {
+void HCSR04Sensor::begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, uint16_t triggerTime, uint16_t triggerWait, eUltraSonicUnlock_t unlock) {
 	if (this->echoCount != echoCount) this->end();
 
 	this->triggerPin = triggerPin;
 	pinMode(triggerPin, OUTPUT);
 
 	this->timeout = timeout;
+	this->triggerTime = triggerTime;
+	this->triggerWait = triggerWait;
 	this->echoCount = echoCount;
 
 	if (this->lastMicroseconds == NULL) this->lastMicroseconds = new long[echoCount];
@@ -82,10 +84,13 @@ void HCSR04Sensor::measureMicroseconds(long* results) {
 	digitalWrite(triggerPin, LOW);
 	delayMicroseconds(4);
 
-	// Hold trigger for 10 microseconds, which is signal for sensor to measure distance.
+	// Hold trigger HIGH for 10 microseconds (default), which signals the sensor to measure distance.
 	digitalWrite(triggerPin, HIGH);
-	delayMicroseconds(11);
+	delayMicroseconds(this->triggerTime);
+
+	// Set trigger LOW again and wait to give the sensor time for sending the signal without interference
 	digitalWrite(triggerPin, LOW);
+	delayMicroseconds(this->triggerWait);
 
 	// Attach interrupts to echo pins for the starting point
 	for (uint8_t i = 0; i < this->echoCount; i++) {

diff --git a/src/HCSR04.h b/src/HCSR04.h
@@ -26,7 +26,8 @@ class HCSR04Sensor {
 		void begin(uint8_t triggerPin, uint8_t echoPin) { begin(triggerPin, new uint8_t[1]{ echoPin }, 1); }
 		void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount) { begin(triggerPin, echoPins, echoCount, 100000, eUltraSonicUnlock_t::unlockSkip); }
 		void begin(uint8_t triggerPin, uint8_t echoPin, uint32_t timeout, eUltraSonicUnlock_t unlock) { begin(triggerPin, new uint8_t[1]{ echoPin }, 1, timeout, unlock); }
-		void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, eUltraSonicUnlock_t unlock);
+		void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, eUltraSonicUnlock_t unlock) { begin(triggerPin, echoPins, echoCount, timeout, 10, 10, unlock); }
+		void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, uint16_t triggerTime, uint16_t triggerWait, eUltraSonicUnlock_t unlock);
 		void end();
 
 		long* measureMicroseconds() { measureMicroseconds(lastMicroseconds); return lastMicroseconds; }
@@ -75,6 +76,8 @@ class HCSR04Sensor {
 		double* lastDistances;
 
 		uint32_t timeout;
+		uint16_t triggerTime = 10; // HC-SR04 needs at least 10µs trigger. Others may need longer trigger pulses.
+		uint16_t triggerWait = 10; // HC-SR04 sends its signal about 200µs. We only wait a small amount to reduce interference, but to not miss anything on slower clock speeds.
 		volatile uint8_t triggerPin;
 		volatile unsigned long* volatile triggerTimes;