You mean, external interrupts.
Yes, a typical school assignment. It's the wrong task, as I've said above. And, actually, should you genuinely need to handle a noisy signal in EXTI, it's actually quite hard to do correctly.
What you are expected to do is:
- have a global variable, say Speed
- I expect you know that each module needs to have clock enabled in RCC, and I expect you've already read RM0090 chapters RCC, GPIO, SYSTICK and EXTI (that's a subchapter of the interrupts chapter)
- set up given pin as GPIO input in GPIO (maybe with pullup or pulldown, depending on the actual circuit)
- map given pin to EXTI in SYSCFG
- enable detection of first edge in EXTI, say falling (if the button shorts to GND and there's a pullup), and enable interrupt on it in the EXTI interrupt mask register
- enable the EXTI interrupt in NVIC
- write an EXTI interrupt handler, which clears the pending register, then - based on current Speed value - clears one edge enable and sets the other, and toggles Speed,
- in main()'s loop, perform the same blink as above, just not based on ButtonInput() but based on Speed
This will work, somehow.
Write the simple version I outlined above, without EXTI, first, and get it running.
Then try to write the interrupt version and debug it until it works somehow. If in trouble, try harder; if in serious trouble, ask.
If you want to go further and understand the problem which is in this approach, draw yourself waveform of a bouncing button http://www.ganssle.com/debouncing.htm then imagine that several of the edges occur in a rapid succession in between consecutive steps taken within the ISR, or in between invocations of the ISR.
JW
