Homework

Homework

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

#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

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)