add Chapter05/gsm_lib

Chapter05/gsm_lib/app/src/main.cpp

@@ -0,0 +1,43 @@
+#include <cstdint>
+
+
+#include <span>
+
+#include <cstdio>
+#include <cstdint>
+
+#include <stm32f072xb.h>
+
+#include <hal.hpp>
+#include <uart_stm32.hpp>
+
+
+
+class gsm_lib{
+    public:
+        gsm_lib(hal::uart &u) : uart_(u) {}
+        void init() {
+            uart_.write("AT\r\n");
+        }
+    private:
+        hal::uart &uart_;
+
+};
+
+
+extern "C" int main(void)
+{
+    hal::init();
+
+    hal::uart_stm32 uart(USART2);
+    uart.init();
+
+    uart.write("Hi from main function!\r\n");
+
+    gsm_lib gsm(uart);
+    gsm.init();
+    
+    while(true)
+    {
+    }
+}