Minor tweaks.

Author: armandas

src/SUMMARY.md

@@ -5,7 +5,8 @@
   - [Hardware information](./setup/hardware.md)
   - [Links](./setup/links.md)
 - [Hello World](./hello_world.md)
-- [Blinky](./blinky.md)
-- [Exercise: working with inputs](./button.md)
+  - [Blinky](./blinky.md)
+  - [Exercise: working with inputs](./button.md)
 - [Interrupts](./interrupt_intro.md)
-- [GPIO Interrupt](./gpio_interrupt.md)
+  - [GPIO Interrupt](./gpio_interrupt.md)
+  - [Exercise: toggle LED with interrupt](./led_with_interrupt.md)

src/button.md

@@ -1,4 +1,4 @@
-# Working with inputs
+# Exercise: working with inputs
 
 We have worked through an example of driving a GPIO output.
 Now it's time for you to try and extend the program to read the GPIO input state.

src/interrupt_intro.md

@@ -1,6 +1,6 @@
 # Interrupts
 
-In the last exercise, we learnt how to read to read a GPIO pin state.
+In the last exercise, we learnt how to read a GPIO pin state.
 However, it's not always desirable to poll the pin state in software.
 This is where interrupts come it. We can ask hardware to notify us whenever the pin state changes.