Initial version

.gitignore

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+.settings
+.cproject
+.project
+example/build
+example/sdkconfig
+.DS_Store

.gitmodules

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+[submodule "libnmea"]
+	path = libnmea
+	url = https://github.com/jacketizer/libnmea

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2015 Jack Engqvist Johansson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# NMEA parser component for ESP32 ESP-IDF
+
+This is a wrapper around [libnmea](https://github.com/jacketizer/libnmea),
+in the form of an [ESP-IDF](https://github.com/espressif/esp-idf) component.
+
+To use, clone the component into the `components` directory of your project,
+or add it as a submodule.
+See [libnmea documentation](https://github.com/jacketizer/libnmea#how-to-use-it)
+for more details.
+
+
+## Example
+
+Example project is provided inside `example` directory. It works the same way
+as `parse_stdin.c` example from libnmea, except that it reads NMEA sentences
+from UART. Connect TXD pin of GPS receiver to GPIO21 of ESP32, build and
+flash the example. Decoded NMEA messages will be displayed in the console.
+
+## Known issues
+
+`strptime` function in newlib is less smart than the one in Glibc, and can not
+parse format strings such as '%H%M%S' (i.e. when there are no separators
+between numeric fields). Therefore date and time fields of NMEA messages
+are not parsed.
+
+## License
+
+[libnmea](https://github.com/jacketizer/libnmea), this component, and the
+example project are licensed under MIT License.

component.mk

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+COMPONENT_SUBMODULES := libnmea
+COMPONENT_SRCDIRS := libnmea/src/nmea libnmea/src/parsers
+COMPONENT_ADD_INCLUDEDIRS := libnmea/src/nmea libnmea/src/parsers
+PARSER_OBJS := $(addprefix libnmea/src/parsers/,\
+		gpgga.o \
+		gpgll.o \
+		gprmc.o \
+	)
+
+COMPONENT_OBJS := $(addprefix libnmea/src/,\
+		nmea/nmea.o \
+		nmea/parser_static.o \
+		parsers/parse.o \
+	) \
+	$(PARSER_OBJS)
+
+define RENAME_SYMBOLS
+	$(OBJCOPY) \
+		--redefine-sym init=nmea_$(1)_init \
+		--redefine-sym parse=nmea_$(1)_parse \
+		--redefine-sym set_default=nmea_$(1)_set_default \
+		--redefine-sym allocate_data=nmea_$(1)_allocate_data \
+		--redefine-sym free_data=nmea_$(1)_free_data \
+		libnmea/src/parsers/$(1).o
+endef
+
+$(COMPONENT_LIBRARY): | rename_symbols
+
+.PHONY: rename_symbols
+
+rename_symbols: | $(PARSER_OBJS)
+	$(call RENAME_SYMBOLS,gpgga)
+	$(call RENAME_SYMBOLS,gpgll)
+	$(call RENAME_SYMBOLS,gprmc)
+
+CPPFLAGS += -DENABLE_GPGLL=1 -DENABLE_GPGGA=1 -DENABLE_GPRMC=1 -DPARSER_COUNT=3

example/Makefile

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+PROJECT_NAME := nmea_example
+
+EXTRA_COMPONENT_DIRS := $(realpath ..)
+
+include $(IDF_PATH)/make/project.mk
+

example/main/nmea_example_main.c

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+/* NMEA parsing example for ESP32.
+ * Based on "parse_stdin.c" example from libnmea.
+ * Copyright (c) 2015 Jack Engqvist Johansson.
+ * Additions Copyright (c) 2017 Ivan Grokhotkov.
+ * See "LICENSE" file in libnmea directory for license.
+ */
+
+#include <stdio.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "driver/uart.h"
+#include "nmea.h"
+#include "gpgll.h"
+#include "gpgga.h"
+#include "gprmc.h"
+
+#define UART_NUM                UART_NUM_2
+#define UART_RX_PIN             21
+#define UART_RX_BUF_SIZE        (1024)
+
+static void uart_setup();
+static void read_and_parse_nmea();
+
+void app_main()
+{
+    uart_setup();
+    read_and_parse_nmea();
+}
+
+static void uart_setup()
+{
+    uart_config_t uart_config = {
+            .baud_rate = 9600,
+            .data_bits = UART_DATA_8_BITS,
+            .parity = UART_PARITY_DISABLE,
+            .stop_bits = UART_STOP_BITS_1,
+            .flow_ctrl = UART_HW_FLOWCTRL_DISABLE
+    };
+    uart_param_config(UART_NUM, &uart_config);
+    uart_set_pin(UART_NUM,
+            UART_PIN_NO_CHANGE, 21,
+            UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
+    uart_driver_install(UART_NUM, UART_RX_BUF_SIZE * 2, 0, 0, NULL, 0);
+}
+
+
+static void read_and_parse_nmea()
+{
+    // Configure a temporary buffer for the incoming data
+    char *buffer = (char*) malloc(UART_RX_BUF_SIZE + 1);
+    char fmt_buf[32];
+    size_t total_bytes = 0;
+    while (1) {
+        // Read data from the UART
+        int read_bytes = uart_read_bytes(UART_NUM,
+                (uint8_t*) buffer + total_bytes,
+                UART_RX_BUF_SIZE - total_bytes, 100 / portTICK_RATE_MS);
+        if (read_bytes <= 0) {
+            continue;
+        }
+
+        nmea_s *data;
+        total_bytes += read_bytes;
+
+        /* find start (a dollar sign) */
+        char* start = memchr(buffer, '$', total_bytes);
+        if (start == NULL) {
+            total_bytes = 0;
+            continue;
+        }
+
+        /* find end of line */
+        char* end = memchr(start, '\r', total_bytes - (start - buffer));
+        if (NULL == end || '\n' != *(++end)) {
+            continue;
+        }
+        end[-1] = NMEA_END_CHAR_1;
+        end[0] = NMEA_END_CHAR_2;
+
+        /* handle data */
+        data = nmea_parse(start, end - start + 1, 0);
+        if (data != NULL) {
+            if (data->errors != 0) {
+                printf("WARN: The sentence struct contains parse errors!\n");
+            }
+
+            if (NMEA_GPGGA == data->type) {
+                printf("GPGGA sentence\n");
+                nmea_gpgga_s *gpgga = (nmea_gpgga_s *) data;
+                printf("Number of satellites: %d\n", gpgga->n_satellites);
+                printf("Altitude: %d %c\n", gpgga->altitude,
+                        gpgga->altitude_unit);
+            }
+
+            if (NMEA_GPGLL == data->type) {
+                printf("GPGLL sentence\n");
+                nmea_gpgll_s *pos = (nmea_gpgll_s *) data;
+                printf("Longitude:\n");
+                printf("  Degrees: %d\n", pos->longitude.degrees);
+                printf("  Minutes: %f\n", pos->longitude.minutes);
+                printf("  Cardinal: %c\n", (char) pos->longitude.cardinal);
+                printf("Latitude:\n");
+                printf("  Degrees: %d\n", pos->latitude.degrees);
+                printf("  Minutes: %f\n", pos->latitude.minutes);
+                printf("  Cardinal: %c\n", (char) pos->latitude.cardinal);
+                strftime(fmt_buf, sizeof(fmt_buf), "%H:%M:%S", &pos->time);
+                printf("Time: %s\n", fmt_buf);
+            }
+
+            if (NMEA_GPRMC == data->type) {
+                printf("GPRMC sentence\n");
+                nmea_gprmc_s *pos = (nmea_gprmc_s *) data;
+                printf("Longitude:\n");
+                printf("  Degrees: %d\n", pos->longitude.degrees);
+                printf("  Minutes: %f\n", pos->longitude.minutes);
+                printf("  Cardinal: %c\n", (char) pos->longitude.cardinal);
+                printf("Latitude:\n");
+                printf("  Degrees: %d\n", pos->latitude.degrees);
+                printf("  Minutes: %f\n", pos->latitude.minutes);
+                printf("  Cardinal: %c\n", (char) pos->latitude.cardinal);
+                strftime(fmt_buf, sizeof(fmt_buf), "%H:%M:%S", &pos->time);
+                printf("Time: %s\n", fmt_buf);
+            }
+
+            nmea_free(data);
+        }
+
+        /* buffer empty? */
+        if (end == buffer + total_bytes) {
+            total_bytes = 0;
+            continue;
+        }
+
+        /* copy rest of buffer to beginning */
+        if (buffer != memmove(buffer, end, total_bytes - (end - buffer))) {
+            total_bytes = 0;
+            continue;
+        }
+
+        total_bytes -= end - buffer;
+    }
+    free(buffer);
+}