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examples/raspi/rf95/shared/gpsMT3339.cpp

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+// -*- mode: C++ -*-
+/*
+ * gpsMT3339.cpp
+ *
+ *  Created on: Jun 11, 2020
+ *      Author: Tilman Glötzner
+ */
+
+#include <gpsMT3339.h>
+#include <stdio.h>
+#include <help_functions.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+
+
+gps_MT3339::gps_MT3339(const char* SerialDevice, pthread_mutex_t* mutex) {
+	// TODO Auto-generated constructor stub
+	this->mutex = mutex;
+
+	gpsDevice = (char*)malloc(strlen(SerialDevice)*sizeof(char));
+	if (gpsDevice == NULL)
+		return;
+	strcpy(gpsDevice,SerialDevice);
+}
+
+gps_MT3339::~gps_MT3339() {
+	// TODO Auto-generated destructor stub
+	stop_reading = true;
+}
+
+char* gps_MT3339::getLatitude() {
+	return latitude;
+}
+
+char* gps_MT3339::getLongitude() {
+	return longitude;
+}
+
+char* gps_MT3339::getTimestamp() {
+	return timestamp;
+}
+
+//function to read gps device of Dragino GPS hat (to be executed by a thread)
+char* gps_MT3339::strnstr(const char *haystack, const char *needle, size_t len)
+{
+        int i;
+        size_t needle_len;
+
+        if (0 == (needle_len = strnlen(needle, len)))
+                return (char *)haystack;
+
+        for (i=0; i<=(int)(len-needle_len); i++)
+        {
+                if ((haystack[0] == needle[0]) &&
+                        (0 == strncmp(haystack, needle, needle_len)))
+                        return (char *)haystack;
+
+                haystack++;
+        }
+        return NULL;
+}
+
+void* gps_MT3339::read_gps(void* ptr)
+{
+	ssize_t n, gga_len,i, comma_count;
+	char* start_ptr;
+	char* end_ptr;
+	char gps_buffer[LEN_GPS_READ_BUFFER];
+	char GPGGA_sentence[LEN_GPS_SENTENCE_BUFFER];
+	int gps_fd = -1;
+	int nofchar;
+	unsigned int empty_read_counter = 0;
+
+	printf("\nGPS READER started\n");
+	print_scheduler();
+	print_scope();
+	memset(gps_buffer,0x00,LEN_GPS_READ_BUFFER);
+
+	while (!stop_reading)
+	{
+		if (gps_fd < 0)
+		{
+			// Open the device in non-blocking mode
+			gps_fd = open(gpsDevice, O_RDWR | O_NONBLOCK);
+			if(gps_fd < 0)
+			{
+				printf("\nWarning: Could not open device file of GPS\n" );
+			}
+		}
+		else
+		{
+			n = read(gps_fd, gps_buffer, 200);
+
+			if (n == 0)
+			{
+				// counter incremented if there was nothing read back
+				empty_read_counter++;
+			}
+			if (n <= 0)
+			{
+				if (((errno != EAGAIN) and (errno != EWOULDBLOCK))
+						|| (empty_read_counter > MAX_EMPTY_READ))
+				{
+				// on read error close file descriptor and restart
+					printf("GPS device being reset\n");
+					strcpy(longitude,"NoValue");
+					strcpy(latitude,"NoValue");
+					strcpy(timestamp,"NoValue");
+
+					close(gps_fd);
+					gps_fd = -1;
+					empty_read_counter = 0;
+					memset(gps_buffer,0x00,LEN_GPS_READ_BUFFER);
+				}
+			}
+			else
+			{
+				// sucessful read => reset counter tracking empty reads
+				empty_read_counter = 0;
+
+				// Scan for sentence read from GPS device containing position
+				start_ptr = strnstr (gps_buffer, "$GPGGA", LEN_GPS_READ_BUFFER);
+				if( start_ptr != NULL)
+				{
+					end_ptr = (char*)memchr(start_ptr, '*',
+							LEN_GPS_READ_BUFFER - (start_ptr - gps_buffer));
+
+					if (end_ptr != NULL)
+					{
+
+						gga_len = (end_ptr-start_ptr) < LEN_GPS_SENTENCE_BUFFER ?
+								(end_ptr-start_ptr) : LEN_GPS_SENTENCE_BUFFER - 1;
+						memcpy(GPGGA_sentence,gps_buffer,gga_len);
+						// make sure that string is delimited
+						GPGGA_sentence[gga_len+1] = '\0';
+						//printf(GPGGA_sentence);
+
+						// extract time and gps coordinates from GPGGA sentence
+						// Sample: GPGGA,193630.000,4846.8772,N,00912.2288,E,1,5,1.57,131.5,M,48.0,M,,
+						comma_count = 0;
+						//printf("%s\n", GPGGA_sentence);
+						start_ptr = strchr(GPGGA_sentence,',') + 1;
+						end_ptr=start_ptr;
+						pthread_mutex_lock(mutex);
+						while (end_ptr != NULL && start_ptr != NULL)
+						{
+							end_ptr = strchr(start_ptr,',');
+							if (end_ptr != NULL)
+							{
+								nofchar = (end_ptr - start_ptr);
+								if (nofchar < LEN_GPS_INFO_BUFFER)
+									end_ptr[0] = '\0';
+								else
+									break;
+
+								int temp = nofchar;
+								if (comma_count == 0)
+								{
+									nofchar = temp < LEN_GPS_INFO_BUFFER ?
+											temp : LEN_GPS_INFO_BUFFER - 1;
+									strncpy(timestamp,start_ptr,nofchar);
+									timestamp[nofchar] = '\0';
+
+								}
+								if (comma_count == 1)
+								{
+									nofchar = temp < LEN_GPS_INFO_BUFFER - 2 ?
+											temp : LEN_GPS_INFO_BUFFER - 2;
+									strncpy(latitude,start_ptr,nofchar);
+									latitude[nofchar] = '\0';
+
+								}
+								if (comma_count == 2)
+								{
+									nofchar = strlen(latitude);
+									strncpy(latitude+nofchar,start_ptr,1);
+									latitude[nofchar+1] = '\0';
+
+								}
+								if (comma_count == 3)
+								{
+									nofchar = temp < LEN_GPS_INFO_BUFFER - 2 ?
+											temp : LEN_GPS_INFO_BUFFER - 2;
+									strncpy(longitude,start_ptr,nofchar);
+									longitude[nofchar] = '\0';
+
+								}
+								if (comma_count == 4)
+								{
+									nofchar = strlen(longitude);
+									strncpy(longitude+nofchar,start_ptr,1);
+									longitude[nofchar+1] = '\0';
+									// all data extracted => bail out
+									end_ptr = NULL;
+									start_ptr = NULL;
+								}
+								start_ptr = end_ptr+1;
+
+								comma_count++;
+							}
+						}
+						pthread_mutex_unlock(mutex);
+					}
+				}
+
+			}
+		}
+		pthread_yield();
+	}
+	free(gpsDevice);
+	close(gps_fd);
+}
+
+void gps_MT3339::stop() {
+	stop_reading = true;
+}
+
+

examples/raspi/rf95/shared/gpsMT3339.h

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+// -*- mode: C++ -*-
+/*
+ * gpsMT3339.h
+ *
+ *  Created on: Jun 11, 2020
+ *      Author: Tilman Glötzner
+ */
+
+#ifndef GPSMT3339_H_
+#define GPSMT3339_H_
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <errno.h>
+#include <string.h>
+
+#define LEN_GPS_READ_BUFFER 255
+#define LEN_GPS_INFO_BUFFER 20
+#define LEN_GPS_SENTENCE_BUFFER 100
+
+// reading the serial port may eventually lock up.
+// MAX_EMPTY_READ determines how many consecutive reads yielding no results, i.e.
+// nofCharRead = 0, may occur before the program tries to reopen the gps device
+#define MAX_EMPTY_READ 15
+#define GPS_DEVICE "/dev/ttyS0"
+
+
+
+class gps_MT3339 {
+public:
+	gps_MT3339(const char* SerialDevice,pthread_mutex_t* mutex);
+	virtual ~gps_MT3339();
+	void*  read_gps(void* ptr);
+	char* getLatitude();
+	char* getLongitude();
+	char* getTimestamp();
+	void stop();
+
+
+private:
+	char *strnstr(const char *haystack, const char *needle, size_t len);
+	char longitude[LEN_GPS_INFO_BUFFER]="NoInit";
+	char latitude[LEN_GPS_INFO_BUFFER]="NoInit";
+	char timestamp[LEN_GPS_INFO_BUFFER]="NoInit";
+	bool stop_reading = false;
+	char *gpsDevice;
+	pthread_mutex_t* mutex;
+};
+
+#endif /* GPSMT3339_H_ */

examples/raspi/rf95/shared/help_functions.cpp

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+// -*- mode: C++ -*-
+/*
+ * help_functions.cpp
+ *
+ *  Created on: Jun 11, 2020
+ *      Author: Tilman Glötzner
+ */
+// help functions
+#include <help_functions.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <pthread.h>
+
+void print_scheduler(void)
+{
+   int schedType;
+
+   schedType = sched_getscheduler(getpid());
+
+   switch(schedType)
+   {
+   case SCHED_FIFO:
+	   printf("Scheduling Policy is SCHED_FIFO\n");
+	   break;
+   case SCHED_OTHER:
+	   printf("Scheduling Policy is SCHED_OTHER\n");
+	   break;
+   case SCHED_RR:
+	   printf("Scheduling Policy is SCHED_RR\n");
+	   break;
+   default:
+	   printf("Scheduling Policy is UNKNOWN\n");
+   }
+}
+
+void print_scope(void)
+{
+	pthread_attr_t tattr;
+	int scope;
+	int ret;
+
+	/* get scope of thread */
+	ret = pthread_attr_getscope(&tattr, &scope);
+	switch(scope)
+	{
+	case PTHREAD_SCOPE_SYSTEM:
+		printf("Scheduling Scope is SYSTEM\n");
+		break;
+	case PTHREAD_SCOPE_PROCESS:
+		printf("Scheduling Scope is PROCESS\n");
+		break;
+	default:
+		printf("Scheduling Scope is UNKNOWN\n");
+	}
+}

examples/raspi/rf95/shared/help_functions.h

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+// -*- mode: C++ -*-
+/*
+ * help_functions.h
+ *
+ *  Created on: Jun 11, 2020
+ *      Author: Tilman Glötzner
+ */
+
+#ifndef HELP_FUNCTIONS_H_
+#define HELP_FUNCTIONS_H_
+void print_scheduler(void);
+void print_scope(void);
+#endif