Adds heartbeat functionality using GPIO

Introduces a heartbeat mechanism to the robot node using GPIO.
This allows for external monitoring of the node's active state.

The heartbeat is implemented using a GPIO pin that toggles
at a regular interval, indicating that the system is running.

Updates CMakeLists to link the project with gpiod libraries
staged locally.
Adds .gitignore entries for local dependencies and PC build directories.

src/RobotNode/.gitignore

@@ -38,4 +38,10 @@
 *.app
 
 # debug information files
-*.dwo
+*.dwo
+
+# Local dependencies
+extern/
+
+# PC-side build directories
+cmake-build-*/

src/RobotNode/CMakeLists.txt

@@ -1,5 +1,4 @@
-# Sets the minimum CMake version required to handle modern C++ features
-cmake_minimum_required(VERSION 3.10) # Version 4.1 doesn't exist yet (standard is 3.x)
+cmake_minimum_required(VERSION 3.10)
 
 # Defines the project name
 project(Dixon)
@@ -7,14 +6,9 @@ project(Dixon)
 # Forces the compiler to use C++20 features
 set(CMAKE_CXX_STANDARD 20)
 
-# Load the PkgConfig tool to find libraries automatically
-find_package(PkgConfig REQUIRED)
-
-# Search for libgpiod v2.x C++ bindings
-pkg_check_modules(GPIOD REQUIRED libgpiodcxx)
-
 # Define the executable and its source files
-add_executable(Dixon main.cpp
+add_executable(Dixon
+        main.cpp
         DixonNodeState.cpp
         DixonNodeState.h
         DixonBrain.cpp
@@ -22,8 +16,14 @@ add_executable(Dixon main.cpp
         CardioCenter/Heart.cpp
         CardioCenter/Heart.h)
 
-# Add the Include directories found by PkgConfig (where the .hpp files live)
-target_include_directories(Dixon PRIVATE ${GPIOD_INCLUDE_DIRS})
+# Header Path: Use the local v2.1 headers staged in the project
+target_include_directories(Dixon PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/extern/libgpiod/include")
 
-# Link the specific libraries found by PkgConfig
-target_link_libraries(Dixon PRIVATE ${GPIOD_LIBRARIES})
+
+# Link the gpiod libraries
+target_link_libraries(Dixon PRIVATE
+        "${CMAKE_CURRENT_SOURCE_DIR}/extern/libgpiod/aarch64/libgpiodcxx.so.2"
+        "${CMAKE_CURRENT_SOURCE_DIR}/extern/libgpiod/aarch64/libgpiod.so.3")
+
+# Tell the linker: "Trust me, the Pi has the rest of the C++ and C libraries"
+target_link_options(Dixon PRIVATE "-Wl,--allow-shlib-undefined")

src/RobotNode/CardioCenter/Heart.cpp

@@ -3,33 +3,40 @@
 
 namespace cardio
 {
-     Heart::Heart(const char* chipName, unsigned int lineOffset)
-    : _isOn(false),
-      _request(setup_request(chipName, lineOffset))
+    Heart::Heart(const char* chipName, unsigned int lineOffset)
+        : chip_(std::string("/dev/") + chipName),
+          isOn_(false),
+          _lastBeat(std::chrono::steady_clock::now()),
+          request_(get_line_request(chip_, lineOffset))
     {
     }
 
     void Heart::beat()
     {
-        _isOn = !_isOn;
-        auto val = _isOn ? gpiod::line::value::ACTIVE : gpiod::line::value::INACTIVE;
-
-        _request.set_value(HEART_LINE_INDEX, val);
+        const auto now = std::chrono::steady_clock::now();
+        if (const auto elapsed = std::chrono::duration_cast<std::chrono::milliseconds>
+            (now - _lastBeat); elapsed.count() >= 500)
+        {
+            isOn_ = !isOn_;
+            const auto val = isOn_ ? gpiod::line::value::ACTIVE : gpiod::line::value::INACTIVE;
+            request_.set_value(DEFAULT_HEART_PIN, val);
+            _lastBeat = now;
+        }
     }
 
-    gpiod::line_request Heart::setup_request(const char* chipName, const unsigned int lineOffset)
-     {
-         std::string chipPath = std::string("/dev/") + chipName;
-         gpiod::chip chip(chipPath);
+    void Heart::stop()
+    {
+        isOn_ = false;
+        request_.set_value(DEFAULT_HEART_PIN, gpiod::line::value::INACTIVE);
+    }
 
-         auto settings = gpiod::line_settings()
-             .set_direction(gpiod::line::direction::OUTPUT);
+    gpiod::line_request Heart::get_line_request(gpiod::chip& chip, const unsigned int lineOffset)
+    {
+        const auto settings = gpiod::line_settings()
+            .set_direction(gpiod::line::direction::OUTPUT);
 
-         auto line_cfg = gpiod::line_config();
-         line_cfg.add_line_settings(lineOffset, settings);
-
-         return chip.prepare_request()
-                    .set_line_config(line_cfg)
-                    .do_request();
-     }
-}
+        return chip.prepare_request()
+            .add_line_settings(lineOffset, settings)
+            .do_request();
+    }
+}

src/RobotNode/CardioCenter/Heart.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <gpiod.hpp>
+#include <chrono>
 
 namespace cardio
 {
@@ -9,13 +10,16 @@ namespace cardio
     public:
         explicit Heart(const char* chipName = GPIO_CHIP_NAME, unsigned int lineOffset = DEFAULT_HEART_PIN);
         void beat();
+        void stop();
 
     private:
+        static gpiod::line_request get_line_request(gpiod::chip&,  unsigned int lineOffset);
         static constexpr auto GPIO_CHIP_NAME = "gpiochip0";
         static constexpr unsigned int DEFAULT_HEART_PIN = 17;
         static constexpr unsigned int HEART_LINE_INDEX = 0;
-        static gpiod::line_request setup_request(const char* chipName, unsigned int lineOffset);
-        bool _isOn;
-        gpiod::line_request _request;
+        std::chrono::steady_clock::time_point _lastBeat;
+        gpiod::chip chip_;
+        bool isOn_;
+        gpiod::line_request request_;
     };
 }

src/RobotNode/DixonBrain.cpp

@@ -4,7 +4,8 @@
 #include <thread>
 
 DixonBrain::DixonBrain()
-    : state_(DixonNodeState::instance())
+    : heart_(),
+      state_(DixonNodeState::instance())
 {
     std::cout << "DixonBrain initialised\n";
 }
@@ -37,6 +38,8 @@ void DixonBrain::stop()
     if (loopThread_.joinable())
         loopThread_.join();
 
+    heart_.stop();
+
     std::cout << "DixonBrain stopped\n";
 }
 
@@ -44,6 +47,7 @@ void DixonBrain::runLoop()
 {
     while (state_.isBrainRunning())
     {
+        heart_.beat();
         // TODO: main control logic
         std::this_thread::sleep_for(std::chrono::milliseconds(10));
     }

src/RobotNode/DixonBrain.h

@@ -1,5 +1,6 @@
 #pragma once
 #include "DixonNodeState.h"
+#include "CardioCenter/Heart.h"
 #include <thread>
 
 class DixonBrain
@@ -14,6 +15,7 @@ public:
 private:
     void runLoop();
 
+    cardio::Heart heart_;
     DixonNodeState& state_;
     std::thread loopThread_;
 };