> For the complete documentation index, see [llms.txt](https://hkust-robotics-team.gitbook.io/hkust-robotics-team-software-tutorial/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hkust-robotics-team.gitbook.io/hkust-robotics-team-software-tutorial/tutorial/tutorial-2-basic-io/homework.md).

# Homework

## **Homework**

Before you start doing homework, You may find these defines in `lcd.h` useful:

```c
#define CHAR_WIDTH 8
#define CHAR_HEIGHT 16

#define MAX_WIDTH 128
#define MAX_HEIGHT 160

#define CHAR_MAX_X_VERTICAL 16
#define CHAR_MAX_Y_VERTICAL 10

#define CHAR_MAX_X_HORIZONTAL 20
#define CHAR_MAX_Y_HORIZONTAL 8

#define CHAR_MAX_X 20  // max between CHAR_MAX_X_VERTICAL and CHAR_MAX_X_HORIZONTAL
#define CHAR_MAX_Y 10  // max between CHAR_MAX_Y_VERTICAL and CHAR_MAX_Y_HORIZONTAL
```

### **Edge Triggering vs Level Triggering**

Consider 2 uses for a single button: (choose BTN1 or BTN2)

#### **Q1 Level Triggering**

* While the button is down, print `Hello, (Your name)` on TFT **(@1)**
* While it is not, flash the LED (at least one LED). **(@1)**
* Two actions should not happen simultaneously.
* Hints:
  * In this case every time the loop comes around, we are concerned with the **current state** (or level) of the buttons GPIO Pin
  * The implementation of the button reading here should be obvious and simple

![](https://i.imgur.com/qSrTmjr.gif) 

> Notice the green button and the green LED

#### **Q2 Edge Triggering**

* We want to print `Hello, (Your name)` for 1 second when the button is pressed, but only once for each press, so holding the button does nothing more. **(@1)**
* When the button is released, we want to flash the LED for 1 second, but again only once for each release. **(@1)**
* The process repeats. i.e. it will print text again if you click the button. **(@1)**
* Keywords:
  * The event of a signal going from low to high is called the ***rising edge*** and the opposite is the ***falling edge***
  * The `gpio_read()` macro gives us the current state, but edge triggering also requires knowledge of the **past state** as well as some logic
* Hints: How can we design some code that can call a function *only* when the button is first clicked? (Rising edge)

#### **Bonus**

* Create a sprite in the middle of the screen. (Can be in any shape other than simple rectangle) **(@1)**
* It will move to the left for one `CHAR_WIDTH` when `BTN1` is clicked and released,
* move to the right for one `CHAR_WIDTH` when `BTN2` is clicked and released. **(@2 for both short press)**