add csrc

lab2/csrc/say_goodbye.c

@@ -0,0 +1,44 @@
+
+void uart_send_char(char c)
+{
+  *((volatile unsigned int *) (0x40000010)) = c;
+  // *((volatile unsigned int *) (0x40000000)) = c;
+}
+
+
+void waste_some_time(int cycle) {
+  unsigned int a = 135;
+  while (cycle--) {
+    a++;
+  }
+}
+
+int main() {
+
+    // const char* s = "abcd";
+    const char* s = "Never gonna give you up~ Never gonna let you down~\n\
+    Never gonna run around and~ desert you~\n";
+
+    while (1) {
+      
+
+      // for (int i = 0; i < ; i++) {
+      //   uart_send_char(s[i]);
+      //   waste_some_time(100);
+      // }
+
+      const char *p = s;
+      while (*p != 0)
+      {
+        uart_send_char(*p);
+        p++;
+        waste_some_time(100);
+      }
+
+      waste_some_time(200);
+
+      break;  // print once, but pressing CPU reset can print again
+    }
+
+    return 0;
+}