CLOCK_MONOTONIC_RAW nehmen statt Zyklen zählen

1 files changed, 38 insertions, 18 deletions

diff --git a/sensor.c b/sensor.c
index f279c87..5da4dee 100644
--- a/sensor.c
+++ b/sensor.c
@@ -31,42 +31,62 @@ int main() {
 
 	drop_privileges();
 
-	// start bit
-	digitalWrite(8, HIGH);
-	usleep(18000);
-	digitalWrite(8, LOW);
-	int bit = -3;
 	char data[5];
-	memset(&data[0], 0, 5);
 	int trials = 3;
+	int bit = 0;
 	while ((bit != 40) || ((data[0]+data[1]+data[2]+data[3]-data[4]) % 255 != 0) || ((data[0]|data[1]|data[2]|data[3]|data[4]) == 0)) {
 		trials--;
 		if (trials < 0) {
 			fprintf(stderr, "Failed to obtain valid reading within 3 trials.\n");
 			return -1;
 		}
-		sleep(2);
-		if (bit > -3)
-			fprintf(stderr, ".");
+		if (trials < 2)
+			sleep(2);
+
+		memset(&data[0], 0, 5);
+
 		// start bit
 		digitalWrite(8, HIGH);
 		usleep(18000);
 		digitalWrite(8, LOW);
-		long int cycles = 0;
-		int last_state = digitalRead(9);
-		// ignore 2 bits: reaction on command + "official" start bit
-		bit = -2;
-		memset(&data[0], 0, 5);
-		while (cycles < 100000) {
-			cycles++;
+
+		struct timespec start_time, stop_time;
+		int last_state = 1;
+		long int low_ns = 0;
+		// ignore first bit
+		bit = -1;
+		if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time) != 0) {
+			perror("clock_gettime start_time failed");
+			return -1;
+		}
+		if (clock_gettime(CLOCK_MONOTONIC_RAW, &stop_time) != 0) {
+			perror("clock_gettime stop_time failed");
+			return -1;
+		}
+		while ((!digitalRead(9)) && (stop_time.tv_sec - start_time.tv_sec + (stop_time.tv_nsec - start_time.tv_nsec) / 1000000000. < 0.0002)) {
+			if (clock_gettime(CLOCK_MONOTONIC_RAW, &stop_time) != 0) {
+				perror("clock_gettime stop_time failed");
+				return -1;
+			}
+		}
+		start_time.tv_sec = stop_time.tv_sec;
+		start_time.tv_nsec = stop_time.tv_nsec;
+		while (stop_time.tv_sec - start_time.tv_sec + (stop_time.tv_nsec - start_time.tv_nsec) / 1000000000. < 0.0002) {
+			if (clock_gettime(CLOCK_MONOTONIC_RAW, &stop_time) != 0) {
+				perror("clock_gettime stop_time failed");
+				return -1;
+			}
 			if (last_state == digitalRead(9))
 				continue;
 			if (last_state == 1) {
-				if ((bit >= 0) && (cycles>300))
+				if ((bit >= 0) && ((stop_time.tv_sec - start_time.tv_sec) * 1000000000 + stop_time.tv_nsec - start_time.tv_nsec > low_ns))
 					data[bit / 8] |= 1 << 7 - (bit % 8);
 				bit++;
+			} else {
+				low_ns = (stop_time.tv_sec - start_time.tv_sec) * 1000000000 + stop_time.tv_nsec - start_time.tv_nsec;
 			}
-			cycles = 0;
+			start_time.tv_sec = stop_time.tv_sec;
+			start_time.tv_nsec = stop_time.tv_nsec;
 			last_state = 1-last_state;
 		}
 	}