add Chapter17

Chapter17/fsm/app/src/main_fsm_simple.cpp

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+#include <cstdint>
+#include <cstdio>
+
+#include <functional>
+
+#include <stm32f072xb.h>
+
+#include <hal.hpp>
+#include <stm32f0xx_hal_uart.hpp>
+#include <uart_stm32.hpp>
+
+#include <retarget.hpp>
+
+enum class ble_state {
+    idle,
+    advertising,
+    connected
+};
+
+enum class ble_event {
+    ble_button_pressed,
+    connection_request,
+    timer_expired
+};
+
+class ble_fsm {
+public:
+    void handle_event(ble_event event) {
+        switch (current_state_) {
+            case ble_state::idle:
+                if (event == ble_event::ble_button_pressed) {
+                    start_advertising();
+                    current_state_ = ble_state::advertising;
+                }
+                break;
+
+            case ble_state::advertising:
+                if (event == ble_event::connection_request) {
+                    current_state_ = ble_state::connected;
+                } else if (event == ble_event::timer_expired) {
+                    stop_advertising();
+                    current_state_ = ble_state::idle;
+                }
+                break;
+
+            case ble_state::connected:
+                if (event == ble_event::ble_button_pressed) {
+                    disconnect();
+                    current_state_ = ble_state::idle;
+                }
+                break;
+            default:
+                break;
+        }
+    }
+
+    ble_state get_state() const {
+        return current_state_;
+    }
+
+private:
+    ble_state current_state_ = ble_state::idle;
+
+    void start_advertising() {
+        printf("Action: start_advertising()\n");
+    }
+
+    void stop_advertising() {
+        printf("Action: stop_advertising()\n");
+    }
+
+    void disconnect() {
+        printf("Action: disconnect()\n");
+    }
+};
+
+static const char* state_to_string(ble_state state) {
+    switch (state) {
+        case ble_state::idle:        return "idle";
+        case ble_state::advertising: return "advertising";
+        case ble_state::connected:   return "connected";
+        default:                     return "unknown";
+    }
+}
+
+int main()
+{
+    hal::init();
+
+    hal::uart_stm32<hal::stm32::uart> uart(USART2);
+    uart.init();
+
+    retarget::set_stdio_uart(&uart);
+
+    ble_fsm my_ble_fsm;
+
+    const auto print_current_state = [&]() {
+        printf("Current State: %s\n", state_to_string(my_ble_fsm.get_state()));
+    };
+
+    print_current_state();
+
+    my_ble_fsm.handle_event(ble_event::ble_button_pressed);
+    print_current_state();
+
+    my_ble_fsm.handle_event(ble_event::connection_request);
+    print_current_state();
+
+    my_ble_fsm.handle_event(ble_event::ble_button_pressed);
+    print_current_state();
+
+
+    while(true)
+    {
+    }
+}