Implement I2C communication with STM

.clang-format

@@ -68,6 +68,10 @@ ForEachMacros:
   - BOOST_FOREACH
 IncludeBlocks: Regroup
 IncludeCategories:
+  # This will hopefully only catch stdlib headers
+  - Regex: "^<[^/]*>"
+    Priority: 5
+    SortPriority: 0
   - Regex: '^[<"]SDL2/'
     Priority: 2
     SortPriority: 0

CMakeLists.txt

@@ -11,6 +11,12 @@ set(CMAKE_CXX_STANDARD 17)
 find_package(SDL2 REQUIRED)
 find_package(SDL2TTF REQUIRED)
 find_package(SDL2IMAGE REQUIRED)
+find_library(I2C_LIBRARY i2c REQUIRED)
+if ("${I2C_LIBRARY}" STREQUAL "I2C_LIBRARY-NOTFOUND")
+    message(FATAL_ERROR "libi2c not found!")
+else()
+    message("libi2c found at ${I2C_LIBRARY}")
+endif()
 
 include(FetchContent)
 
@@ -48,6 +54,7 @@ add_executable(
     stw-display
     src/main.cpp
     src/App.cpp
+    src/AppState.cpp
     src/View.cpp
     src/MissionSelect.cpp
     src/widgets.cpp
@@ -67,6 +74,7 @@ target_link_libraries(
     ${SDL2_LIBRARIES}
     ${SDL2TTF_LIBRARY}
     ${SDL2IMAGE_LIBRARY}
+    ${I2C_LIBRARY}
     fmt
     spdlog::spdlog)
 add_dependencies(stw-display fmt)

include/App.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "AppState.h"
 #include "MissionSelect.h"
 #include "defines.h"
 
@@ -7,8 +8,6 @@
 
 #include <memory>
 
-enum class AppView { MISSION_SELECT, AMI, DRIVER, TESTING };
-
 class SDLManager {
 public:
   SDLManager();
@@ -24,6 +23,7 @@ public:
 
 private:
   void init_sdl();
+  void init_state();
 
   void handle_events();
   void render();
@@ -33,10 +33,10 @@ private:
   // others and its destructor is called after the others.
   SDLManager sdl_manager;
 
+  std::unique_ptr<AppState> state;
   std::unique_ptr<MissionSelect> mission_select;
 
   bool running;
-  AppView view;
 
   SDL_Window* window;
   SDL_Renderer* renderer;

include/AppState.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <fmt/ostream.h>
+
+#include <optional>
+#include <ostream>
+#include <string>
+
+constexpr int I2C_SLAVE_ADDR = 0x20;
+constexpr int I2C_POLL_COMMAND = 0x00;
+
+enum class AppView { MISSION_SELECT, AMI, DRIVER, TESTING };
+std::ostream& operator<<(std::ostream& os, AppView view);
+
+class AppState {
+public:
+  AppState(const std::string& i2c_dev_path);
+  ~AppState();
+
+  void poll();
+
+  AppView get_view();
+
+private:
+  // This is optional so that we can still run the code on a PC without I2C
+  std::optional<int> i2c_dev_file;
+
+  AppView view;
+};

src/App.cpp

@@ -1,5 +1,6 @@
 #include "App.h"
 
+#include "AppState.h"
 #include "MissionSelect.h"
 #include "events.h"
 
@@ -13,10 +14,14 @@
 #include <fmt/format.h>
 #include <spdlog/spdlog.h>
 
+#include <memory>
 #include <queue>
 #include <stdexcept>
 
-App::App() : view{AppView::MISSION_SELECT} { init_sdl(); }
+App::App() {
+  init_sdl();
+  init_state();
+}
 
 App::~App() {
   // Destroy window
@@ -43,6 +48,14 @@ void App::init_sdl() {
   }
 }
 
+void App::init_state() {
+  try {
+    state = std::make_unique<AppState>("/dev/i2c-3");
+  } catch (const std::runtime_error& e) {
+    spdlog::error("Couldn't create AppState: {}", e.what());
+  }
+}
+
 int App::run() {
   mission_select = std::make_unique<MissionSelect>(renderer);
 
@@ -58,6 +71,10 @@ int App::run() {
       frames = 0;
     }
 
+    if (state != nullptr) {
+      state->poll();
+    }
+
     handle_events();
     render();
 
@@ -93,22 +110,24 @@ void App::handle_events() {
     }
   }
 
+  AppView view = state->get_view();
   switch (view) {
   case AppView::MISSION_SELECT:
     mission_select->handle_events(events);
     break;
   default:
-    throw std::runtime_error(fmt::format("Unknown view: {}", (int)view));
+    throw std::runtime_error(fmt::format("Unknown view: {}", view));
   }
 }
 
 void App::render() {
+  AppView view = state->get_view();
   switch (view) {
   case AppView::MISSION_SELECT:
     mission_select->draw();
     break;
   default:
-    throw std::runtime_error(fmt::format("Unknown view: {}", (int)view));
+    throw std::runtime_error(fmt::format("Unknown view: {}", view));
   }
   SDL_RenderPresent(renderer);
 }

src/AppState.cpp

@@ -0,0 +1,69 @@
+#include "AppState.h"
+
+#include <fmt/format.h>
+#include <spdlog/spdlog.h>
+
+#include <fcntl.h>
+#include <optional>
+extern "C" {
+#include <i2c/smbus.h>
+}
+#include <linux/i2c-dev.h>
+#include <sys/ioctl.h>
+
+#include <cstdint>
+#include <stdexcept>
+#include <unistd.h>
+
+std::ostream& operator<<(std::ostream& os, AppView view) {
+  switch (view) {
+  case AppView::MISSION_SELECT:
+    return os << "MISSION_SELECT";
+  case AppView::AMI:
+    return os << "AMI";
+  case AppView::DRIVER:
+    return os << "DRIVER";
+  case AppView::TESTING:
+    return os << "TESTING";
+  default:
+    return os << "UNKNOWN_VIEW[" << static_cast<int>(view) << "]";
+  }
+}
+
+AppState::AppState(const std::string& i2c_dev_path)
+    : view{AppView::MISSION_SELECT} {
+  i2c_dev_file = open(i2c_dev_path.c_str(), O_RDWR);
+  if (i2c_dev_file < 0) {
+    spdlog::error("Couldn't open I2C device: {}", errno);
+    i2c_dev_file = std::nullopt;
+    return;
+  }
+
+  if (ioctl(*i2c_dev_file, I2C_SLAVE, I2C_SLAVE_ADDR) < 0) {
+    spdlog::error("Couldn't set I2C slave address: {}", errno);
+    close(*i2c_dev_file);
+    i2c_dev_file = std::nullopt;
+  }
+}
+
+AppState::~AppState() {
+  if (i2c_dev_file) {
+    close(*i2c_dev_file);
+  }
+}
+
+void AppState::poll() {
+  if (!i2c_dev_file) {
+    return;
+  }
+
+  uint8_t data[32];
+  int count = i2c_smbus_read_block_data(*i2c_dev_file, I2C_POLL_COMMAND, data);
+  if (count < 0) {
+    throw std::runtime_error(fmt::format("Couldn't poll I2C slave: {}", errno));
+  }
+  view = static_cast<AppView>(data[0]);
+  spdlog::info("View after poll: {}", view);
+}
+
+AppView AppState::get_view() { return view; }