u2_usb: add watchdog

u2_usb.c

@@ -25,6 +25,8 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdarg.h>
+#include <unistd.h>
+#include <signal.h>
 #include <hidapi/hidapi.h>
 #include <netdb.h>
 
@@ -39,6 +41,15 @@ static void die(const char* format, ...)
 	exit(1);
 }
 
+/* watchdog called after alarm timeout
+ * @param[in] sig alarm signal
+ */
+static void watchdog(int sig)
+{
+	(void)sig; // argument not used
+	die("exiting due to inactivity\n");
+}
+
 /* original trigger message from vendor software
 "\xff\x55\x58\x8a\x13\x79\x06\x57\x1a\x01\x0a\x02\x00\x00\x00\x00" \
 "\x5e\x00\x00\x00\xff\x55\x2f\xb2\x8b\xdc\x5a\xd4\x1a\x2c\xa4\x00" \
@@ -121,6 +132,9 @@ int main(int argc, char* argv[])
 		}
 	}
 
+	signal(SIGALRM, watchdog); // setup watchdog
+	alarm(5); // start watchdog (in case connecting to the U2 gets stuck)
+
 	// UDP socket to send data to influxdb
 	int influxdb_fd = 0;
 	struct addrinfo* res = 0;
@@ -200,8 +214,11 @@ int main(int argc, char* argv[])
 			if (debug) {
 				printf("trigger measurement\n");
 			}
+			continue;
 		}
 
+		alarm(5); // restart watchdog
+
 		// parse measurement values
 		meas.seconds = meas.payload[2];
 		meas.increment1 = meas.payload[3];