Implement I2C communication with STM

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; }