update readme

README.md

@@ -4,5 +4,20 @@ So far:
 * MyNewProject - blinking lights
 * Calculator - not finished
 
+<hr>
+
+# Notes
+
+### Changes to generated code
+After generating `Core/Src/main.c` in any project, we have typically had to
+comment the following lines out:
+```C
+osThreadDef(defaultTask, startDefaultTask, osPriorityNormal, 0, 4096);
+defaultTaskHandle = osThreadCreate(osThread(defaultTask), NULL);
+osKernelStart();
+```
+These are related to RTOS, but more importantly, they prevent `while (1)`
+(user generated code loop) from running immediately like we usually want.
+
 <hr>
 <small>not for release</small>