Template:LIBGPIOD V2 C EXAMPLE: Difference between revisions

Latest revision as of 19:52, 10 March 2025

libgpiod C++ Application

[ libgpiod] provides bindings for C++, Python and Rust applications. C++ examples are available in the libgpiod [/tree/bindings/cxx/examples /tree/bindings/cxx/examples ] directory.

Below is a simple C application demonstrating how to use the bindings with GPIO0_IO05:

Makefile:

LDFLAGS = -lgpiodcxx -lgpiod

# Nome do executável e arquivos fonte
TARGET = main
SRCS = main.cpp

all: $(TARGET)

$(TARGET): $(SRCS)
	$(CXX) $(SRCS) $(LDFLAGS) -o $(TARGET)

clean:
	rm -f $(TARGET)

main.cpp

// SPDX-License-Identifier: GPL-2.0-or-later
// SPDX-FileCopyrightText: 2023 Kent Gibson <warthog618@gmail.com>

/* Minimal example of reading a single line. */

#include <cstdlib>
#include <filesystem>
#include <gpiod.hpp>
#include <iostream>

namespace {

/* Example configuration - customize to suit your situation */
const ::std::filesystem::path chip_path("/dev/gpiochip0");
const ::gpiod::line::offset line_offset = 5;

} /* namespace */

int main()
{
	auto request = ::gpiod::chip(chip_path)
			       .prepare_request()
			       .set_consumer("get-line-value")
			       .add_line_settings(
				       line_offset,
				       ::gpiod::line_settings().set_direction(
					       ::gpiod::line::direction::INPUT))
			       .do_request();

	::std::cout << line_offset << "="
		    << (request.get_value(line_offset) ==
					::gpiod::line::value::ACTIVE ?
				"Active" :
				"Inactive")
		    << ::std::endl;

	return EXIT_SUCCESS;
}

@@ Line 1: / Line 1: @@
-== libgpiod C Application ==
+== libgpiod C++ Application ==
-[{{#var:LIBGPIOD_URL}} libgpiod] provides bindings for C/C++ applications. C++ examples are available in the libgpiod [{{#var:LIBGPIOD_URL}}/tree/bindings/cxx/examples /tree/bindings/cxx/examples ] directory.
+[{{#var:LIBGPIOD_URL}} libgpiod] provides bindings for C++, Python and Rust applications. C++ examples are available in the libgpiod [{{#var:LIBGPIOD_URL}}/tree/bindings/cxx/examples /tree/bindings/cxx/examples ] directory.
-Below is a simple C application demonstrating how to use the bindings with GPIO4_IO21:
+Below is a simple C application demonstrating how to use the bindings with GPIO0_IO05:
 '''Makefile:'''
 <pre>
-LDFLAGS = -lgpiod
+LDFLAGS = -lgpiodcxx -lgpiod
+# Nome do executável e arquivos fonte
 TARGET = main
-SRCS = main.c
+SRCS = main.cpp
 all: $(TARGET)
@@ Line 21: / Line 22: @@
 </pre>
-'''main.c'''
+'''main.cpp'''
 <pre>
 // SPDX-License-Identifier: GPL-2.0-or-later
@@ Line 28: / Line 29: @@
 /* Minimal example of reading a single line. */
-#include <errno.h>
+#include <cstdlib>
-#include <gpiod.h>
+#include <filesystem>
-#include <stdio.h>
+#include <gpiod.hpp>
-#include <stdlib.h>
+#include <iostream>
-#include <string.h>
-/* Request a line as input. */
+namespace {
-static struct gpiod_line_request *request_input_line(const char *chip_path,
-						     unsigned int offset,
-						     const char *consumer)
-{
-	struct gpiod_request_config *req_cfg = NULL;
-	struct gpiod_line_request *request = NULL;
-	struct gpiod_line_settings *settings;
-	struct gpiod_line_config *line_cfg;
-	struct gpiod_chip *chip;
-	int ret;
-	chip = gpiod_chip_open(chip_path);
+/* Example configuration - customize to suit your situation */
-	if (!chip)
+const ::std::filesystem::path chip_path("/dev/gpiochip0");
-		return NULL;
+const ::gpiod::line::offset line_offset = 5;
-	settings = gpiod_line_settings_new();
+} /* namespace */
-	if (!settings)
-		goto close_chip;
-	gpiod_line_settings_set_direction(settings, GPIOD_LINE_DIRECTION_INPUT);
+int main()
+{
-	line_cfg = gpiod_line_config_new();
+	auto request = ::gpiod::chip(chip_path)
-	if (!line_cfg)
+			       .prepare_request()
-		goto free_settings;
+			       .set_consumer("get-line-value")
+			       .add_line_settings(
-	ret = gpiod_line_config_add_line_settings(line_cfg, &offset, 1,
+				       line_offset,
-						  settings);
+				       ::gpiod::line_settings().set_direction(
-	if (ret)
+					       ::gpiod::line::direction::INPUT))
-		goto free_line_config;
+			       .do_request();
-	if (consumer) {
-		req_cfg = gpiod_request_config_new();
-		if (!req_cfg)
-			goto free_line_config;
-		gpiod_request_config_set_consumer(req_cfg, consumer);
-	}
-	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);
-	gpiod_request_config_free(req_cfg);
-free_line_config:
-	gpiod_line_config_free(line_cfg);
-free_settings:
-	gpiod_line_settings_free(settings);
-close_chip:
-	gpiod_chip_close(chip);
-	return request;
+	::std::cout << line_offset << "="
-}
+		    << (request.get_value(line_offset) ==
+					::gpiod::line::value::ACTIVE ?
-static int print_value(unsigned int offset, enum gpiod_line_value value)
+				"Active" :
-{
+				"Inactive")
-	if (value == GPIOD_LINE_VALUE_ACTIVE)
+		    << ::std::endl;
-		printf("%d=Active\n", offset);
-	else if (value == GPIOD_LINE_VALUE_INACTIVE) {
-		printf("%d=Inactive\n", offset);
-	} else {
-		fprintf(stderr, "error reading value: %s\n",
-			strerror(errno));
-		return EXIT_FAILURE;
-	}
 	return EXIT_SUCCESS;
-}
-int main(void)
-{
-	/* Example configuration - customize to suit your situation. */
-	static const char *const chip_path = "/dev/gpiochip3";
-	static const unsigned int line_offset = 21;
-	struct gpiod_line_request *request;
-	enum gpiod_line_value value;
-	int ret;
-	request = request_input_line(chip_path, line_offset, "get-line-value");
-	if (!request) {
-		fprintf(stderr, "failed to request line: %s\n",
-			strerror(errno));
-		return EXIT_FAILURE;
-	}
-	value = gpiod_line_request_get_value(request, line_offset);
-	ret = print_value(line_offset, value);
-	/* not strictly required here, but if the app wasn't exiting... */
-	gpiod_line_request_release(request);
-	return ret;
 }
 </pre>