Getting Started

Chapter 10: C Structures

he Display state

ystick is clicked down, then I enter the AVR Butterfly

ble

put st

uctures to keep track of it. First we define two generic structures that we will

ter instantiate for each specific state, input, and next state data set.

rfly software was written using an IAR

complier. There are a lot of notes in the code

Thomas who did the porting.

the discussion as they are not

ere.]

nd menu

e three relevant variables:

gned char state; // the current state

_P pText; // pointer to some text in FLASH memory

char (*pFunc)(char input); // pointer to a function

MENU_STATE;

the current state

the input stimulus

} MENU_NEXTSTATE;

need to find the function that

ified state. The MENU_NEXTSTATE structure

state given the present state and an

TE structure first. We see that we can have 256

ame and a function pointer with each. The

character input value and returning a

if the joystick is clicked left, then I enter t
else if the jo
state

For each state, we must know the next state that we must enter for each possi
in ate. That’s going to be a lot of data so lets use what we’ve learned about
str
la

[ASIDE: As mentioned before, the B
AVR

utte
compiler and ported to the Win
that begin // mt. This is a note added by Martin
Kudo’s to Martin, but I’ve removed his notes from
relevant to what we are trying to learn h

In Menu.h we f
ext sta

ind the definitions of data structures for our menu state a
n te that contains th

typedef struct PROGMEM

{

unsi

PGM

}

typedef str

{

uct PROGMEM

unsigned char state; //

unsigned char input; /

unsigned char nextstate; // the resulting next state

The MENU_STATE structure
c

provides the data we
should be run while in the spe
provides the data we need to find the next
input state.

Let’s deal with the MENU_STA
states, and can associate a text n
function pointer is defined as taking a