Difference between revisions of "Debouncing Multiple-Keypress PRGM GetKey"
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| − | The below code is not a single function, but rather a group of functions for fulfilling a single purpose: providing key debouncing and multi-keypress detection to the PRGM GetKey function | + | == Synopsis == |
| + | The below code is not a single function, but rather a group of functions for fulfilling a single purpose: providing key debouncing and multi-keypress detection to the PRGM GetKey function. The needed function and variable declarations are as follows: | ||
| + | |||
| + | === Definition === | ||
const unsigned short* keyboard_register = (unsigned short*)0xA44B0000; | const unsigned short* keyboard_register = (unsigned short*)0xA44B0000; | ||
| − | unsigned short | + | unsigned short lastkey[8]; |
| − | unsigned short | + | unsigned short holdkey[8]; |
void keyupdate(void) { | void keyupdate(void) { | ||
memcpy(holdkey, lastkey, sizeof(unsigned short)*8); | memcpy(holdkey, lastkey, sizeof(unsigned short)*8); | ||
| − | |||
memcpy(lastkey, keyboard_register, sizeof(unsigned short)*8); | memcpy(lastkey, keyboard_register, sizeof(unsigned short)*8); | ||
| − | |||
} | } | ||
int keydownlast(int basic_keycode) { | int keydownlast(int basic_keycode) { | ||
| Line 31: | Line 32: | ||
These functions are used to check the current state of a key in the key array during the current loop runthrough, or check the value from the last loop. These use the KEY_PRGM_<key> key codes, and should be used in something like a game loop to provide clean debouncing. Here is an example of these functions at work in an example game loop: | These functions are used to check the current state of a key in the key array during the current loop runthrough, or check the value from the last loop. These use the KEY_PRGM_<key> key codes, and should be used in something like a game loop to provide clean debouncing. Here is an example of these functions at work in an example game loop: | ||
| − | + | while(running) { | |
keyupdate(); // update both key arrays | keyupdate(); // update both key arrays | ||
| Line 48: | Line 49: | ||
if(!keydownlast(KEY_PRGM_UP) && keydownhold(KEY_PRGM_UP)) | if(!keydownlast(KEY_PRGM_UP) && keydownhold(KEY_PRGM_UP)) | ||
} | } | ||
| + | |||
| + | === Inputs === | ||
| + | keyupdate: None | ||
| + | |||
| + | keydownlast: int (KEY_PRGM_<key> keycode) | ||
| + | |||
| + | keydownhold: int (KEY_PRGM_<key> keycode) | ||
| + | |||
| + | === Outputs === | ||
| + | keyupdate: None | ||
| + | |||
| + | keydownlast: 1 if key has been pressed during last keyupdate() call, 0 otherwise | ||
| + | |||
| + | keydownhold: 1 if key has been pressed two keyupdate() calls ago, 0 otherwise | ||
| + | |||
| + | == Comments == | ||
| + | It's a bit more wordy to use than its simple PRGM GetKey sibling, but it's also very flexible and can even be used to check for pseudo keydown/keyup key events. It also reads directly from keyboard hardware ports, so it's very fast and doesn't rely on the OS's control. | ||
| + | [[Category: Useful Routines]] | ||
Latest revision as of 17:12, 18 April 2014
Synopsis
The below code is not a single function, but rather a group of functions for fulfilling a single purpose: providing key debouncing and multi-keypress detection to the PRGM GetKey function. The needed function and variable declarations are as follows:
Definition
const unsigned short* keyboard_register = (unsigned short*)0xA44B0000;
unsigned short lastkey[8];
unsigned short holdkey[8];
void keyupdate(void) {
memcpy(holdkey, lastkey, sizeof(unsigned short)*8);
memcpy(lastkey, keyboard_register, sizeof(unsigned short)*8);
}
int keydownlast(int basic_keycode) {
int row, col, word, bit;
row = basic_keycode%10;
col = basic_keycode/10-1;
word = row>>1;
bit = col + 8*(row&1);
return (0 != (lastkey[word] & 1<<bit));
}
int keydownhold(int basic_keycode) {
int row, col, word, bit;
row = basic_keycode%10;
col = basic_keycode/10-1;
word = row>>1;
bit = col + 8*(row&1);
return (0 != (holdkey[word] & 1<<bit));
}
These functions are used to check the current state of a key in the key array during the current loop runthrough, or check the value from the last loop. These use the KEY_PRGM_<key> key codes, and should be used in something like a game loop to provide clean debouncing. Here is an example of these functions at work in an example game loop:
while(running) {
keyupdate(); // update both key arrays
...
// checking to see if the up key has been held down for a while
if(keydownlast(KEY_PRGM_UP) && keydownhold(KEY_PRGM_UP))
// checking to see if the up key has not been held down for a while
if(!keydownlast(KEY_PRGM_UP) && !keydownhold(KEY_PRGM_UP))
// checking to see if the up key has just been pressed
if(keydownlast(KEY_PRGM_UP) && !keydownhold(KEY_PRGM_UP))
// checking to see if the up key has just been released
if(!keydownlast(KEY_PRGM_UP) && keydownhold(KEY_PRGM_UP))
}
Inputs
keyupdate: None
keydownlast: int (KEY_PRGM_<key> keycode)
keydownhold: int (KEY_PRGM_<key> keycode)
Outputs
keyupdate: None
keydownlast: 1 if key has been pressed during last keyupdate() call, 0 otherwise
keydownhold: 1 if key has been pressed two keyupdate() calls ago, 0 otherwise
Comments
It's a bit more wordy to use than its simple PRGM GetKey sibling, but it's also very flexible and can even be used to check for pseudo keydown/keyup key events. It also reads directly from keyboard hardware ports, so it's very fast and doesn't rely on the OS's control.
