...I Know how to blink a led.( I build an led chaser too!) I would say that I know a bit about serial communication. But I DO need to learn about PWM and interrupts. (NO idea what interrupts are, but I'll google it!)
This is exactly what I mean. No offence, but the way you know how to blink a led, is by copy/paste internet text into some software, connect a cable and push the "send" button.
The time when I didn't know about interrupts, I considered myself being on level "zero" in the world of microcrontrollers.
You will now have to start learning all the other ways to blink that led.
-try this: close internet, the books and examples, and write/type your software yourself, from zero, without libraries.
-blink 8 leds, all together, but at another frequency.
-blink a led at 1HZ, but make sure input from a pushbutton is always immediately sent to rs232.
-blink the led at a rate that is received by serial communication.
-make a led dimmer with pwm.
-Make it blink or dim using interrupts, so less processor performance is used, and other software can run also.
After that, you are ready to take another step, and ready for start thinking about measurement and control.