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Handle echo pulse edges in correct order.

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only emit a new distance value if echo pulse edges trigger in the right order. Fixes #1
This commit is contained in:
mandlm 2017-10-15 13:11:46 +02:00 committed by mandlm
parent 94611f2381
commit 4811ab8239
2 changed files with 7 additions and 6 deletions
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1
.gitignore vendored
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@ -1,2 +1,3 @@
build*/ build*/
*.user *.user
.*.swp

12
source/distancethread.cpp
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@ -2,7 +2,7 @@
#include <wiringPi.h> #include <wiringPi.h>
volatile unsigned int timestampHigh = 0; volatile unsigned int timestampHigh = 0;
volatile unsigned int timestampLow = 0; volatile unsigned int pulseLength = 0;
DistanceThread::DistanceThread() DistanceThread::DistanceThread()
{ {
@ -19,9 +19,10 @@ void DistanceThread::run()
{ {
timestampHigh = micros(); timestampHigh = micros();
} }
else else if (timestampHigh != 0)
{ {
timestampLow = micros(); pulseLength = micros() - timestampHigh;
timestampHigh = 0;
} }
}); });
@ -32,10 +33,9 @@ void DistanceThread::run()
digitalWrite(m_triggerPin, LOW); digitalWrite(m_triggerPin, LOW);
delayMicroseconds(40); delayMicroseconds(40);
unsigned int delayUS = timestampLow - timestampHigh; if (pulseLength < 25e3)
if (delayUS < 25e3)
{ {
emit distanceUpdated(delayUS / 0.58); emit distanceUpdated(pulseLength / 0.58);
} }
delay(100); delay(100);