I found this code over at adafruit that's great for taking the work out of my 5-way joystick (5 buttons). I have now idea how the heart of it works, as I'm only familiar with the Arduino IDE, with no C++ or experience. It calls functions and stuff to trigger a timer to check the buttons independently of my code.
I don't really like not knowing how parts of my code work, but I think this is way over my head. So I would just like to know that this timer interrupt thing will work with all my other code. Mainly, I'll be checking an RTC over SPI every few seconds. This timer interrupt won't butt in on that and make a glitch at random times, will it?
Thanks,
here a copy of the code from adafruit.
#define DEBOUNCE 10 // button debouncer, how many ms to debounce, 5+ ms is usually plenty
// here is where we define the buttons that we'll use. button "1" is the first, button "6" is the 6th, etc
byte buttons[] = {14, 15, 16, 17, 18, 19}; // the analog 0-5 pins are also known as 14-19
// This handy macro lets us determine how big the array up above is, by checking the size
#define NUMBUTTONS sizeof(buttons)
// we will track if a button is just pressed, just released, or 'currently pressed'
volatile byte pressed[NUMBUTTONS], justpressed[NUMBUTTONS], justreleased[NUMBUTTONS];
void setup() {
byte i;
// set up serial port
Serial.begin(9600);
Serial.print("Button checker with ");
Serial.print(NUMBUTTONS, DEC);
Serial.println(" buttons");
// pin13 LED
pinMode(13, OUTPUT);
// Make input & enable pull-up resistors on switch pins
for (i=0; i< NUMBUTTONS; i++) {
pinMode(buttons[i], INPUT);
digitalWrite(buttons[i], HIGH);
}
// Run timer2 interrupt every 15 ms
TCCR2A = 0;
TCCR2B = 1<<CS22 | 1<<CS21 | 1<<CS20;
//Timer2 Overflow Interrupt Enable
TIMSK2 |= 1<<TOIE2;
}
SIGNAL(TIMER2_OVF_vect) {
check_switches();
}
void check_switches()
{
static byte previousstate[NUMBUTTONS];
static byte currentstate[NUMBUTTONS];
static long lasttime;
byte index;
if (millis() < lasttime) {
// we wrapped around, lets just try again
lasttime = millis();
}
if ((lasttime + DEBOUNCE) > millis()) {
// not enough time has passed to debounce
return;
}
// ok we have waited DEBOUNCE milliseconds, lets reset the timer
lasttime = millis();
for (index = 0; index < NUMBUTTONS; index++) {
currentstate[index] = digitalRead(buttons[index]); // read the button
/*
Serial.print(index, DEC);
Serial.print(": cstate=");
Serial.print(currentstate[index], DEC);
Serial.print(", pstate=");
Serial.print(previousstate[index], DEC);
Serial.print(", press=");
*/
if (currentstate[index] == previousstate[index]) {
if ((pressed[index] == LOW) && (currentstate[index] == LOW)) {
// just pressed
justpressed[index] = 1;
}
else if ((pressed[index] == HIGH) && (currentstate[index] == HIGH)) {
// just released
justreleased[index] = 1;
}
pressed[index] = !currentstate[index]; // remember, digital HIGH means NOT pressed
}
//Serial.println(pressed[index], DEC);
previousstate[index] = currentstate[index]; // keep a running tally of the buttons
}
}
void loop() {
for (byte i = 0; i < NUMBUTTONS; i++) {
if (justpressed[i]) {
justpressed[i] = 0;
Serial.print(i, DEC);
Serial.println(" Just pressed");
// remember, check_switches() will CLEAR the 'just pressed' flag
}
if (justreleased[i]) {
justreleased[i] = 0;
Serial.print(i, DEC);
Serial.println(" Just released");
// remember, check_switches() will CLEAR the 'just pressed' flag
}
if (pressed[i]) {
Serial.print(i, DEC);
Serial.println(" pressed");
// is the button pressed down at this moment
}
}
}
