Creating a Tap Tempo (help needed)

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1

Hello,
I have a arduino Deicimila board, and i have great fun using it.
Now i would like to make a LFO (through PWM) using Tap Tempo.

That is that you have to tap the momantary switch twice to callculate the time for the PWM.
I have a good LFO running from pin9 (PWM) and i have a Potentiometer for the speed/rate control.
But now i would like to do that with a Tap Tempo switch.
How should i set this up in the software?
Could anybody give some idea's.

best regards
Ronald

2

you'll have to take the time between two presses to calculate the differnce in Milliseconds.
so the first thing is to distinguish between the 1st and the 2nd press.
use a variable to count them.

int numberOfButtonPresses = 0;
long int time_1;
long int time_2;

long int time_difference; //thats what your looking for

now in your main loop wait for the action.

if (buttonPressed && numberOfButtonPresses== 0 ) { //first action
//maybe reset millis ... resetMilis();
//store the "start time"
time_1 = millis();
numberOfButtonPresses++;
}

if (buttonPressed && numberOfButtonPresses== 1 ) { //SECOND action
//store the "end time"
time_2 = millis();
time_difference=time_2 - time_1;
numberOfButtonPresses=0; //reset button counter for the next time
}

3

you'll have to take the time between two presses to calculate the differnce in Milliseconds.
so the first thing is to distinguish between the 1st and the 2nd press.
use a variable to count them.

int numberOfButtonPresses = 0;
long int time_1;
long int time_2;

long int time_difference; //thats what your looking for

now in your main loop wait for the action.

if (buttonPressed && numberOfButtonPresses== 0 ) { //first action
//maybe reset millis ... resetMilis();
//store the "start time"
time_1 = millis();
numberOfButtonPresses++;
}

if (buttonPressed && numberOfButtonPresses== 1 ) { //SECOND action
//store the "end time"
time_2 = millis();
time_difference=time_2 - time_1;
numberOfButtonPresses=0; //reset button counter for the next time
}

HEllo,
Thank you very much, that's a big help.

Now i have an other question. I read that the millis() starts on startup. So on the first buttonPressed i need to reset the millis(), right?
But (sorry if this is a dump question) how do i reset the millis() and asign time_1 to the start time?
The same for time_2 and end time?

Is this also tru that you don't need an interrupt on overflow (because the millis() overflows on 9 hours .... )?

Thanks is advance.

regards
Ronald

4

Oke i have put some work in it to try things out and make things work and understand it better, this is what i got so far:

/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  • TTLFO - an Arduino-based Tap Tempo LFO
  • RonaldB, 20-08-2008
*/

const int pinPwmout = 9;
int buttonPressed = 2;
int ledPin = 13;
int val;
int numberOfButtonPresses = 0;
long int startTime;
long int endTime;

long int tempo; //time between tabs

void setup ()
{
pinMode(pinPwmout, OUTPUT);
pinMode(buttonPressed, INPUT);
pinMode(ledPin, OUTPUT);
}

extern volatile unsigned long timer0_overflow_count;

void resetMillis()
{
cli(); // disable interrupts
timer0_overflow_count = 0;
sei(); // enable interrupts
} 

void loop()
{
if(buttonPressed && numberOfButtonPresses == 0){
resetMillis();
startTime = millis(); //store start time
numberOfButtonPresses++;
}
if(buttonPressed && numberOfButtonPresses == 1) {
endTime = millis(); //store the "end time"
tempo = 2000;
numberOfButtonPresses=0; //reset button counter for the next time

digitalWrite (pinPwmout, HIGH); //square wave output on PWM pin 9
delay (tempo);
digitalWrite (pinPwmout, LOW);
delay (tempo);
}
}

I have put a delay of 2000 in the tempo just to see if that is working.
Well the PWM is working at 2000ms on and off, so thats working.

Only when I put in this line:

tempo = startTime - endTime

The LED is flashing really fast (at least i think). Could this be a debounce thing?

How would i get this thing work so it reads the correct tempo between tabs.

thanks in advance

best regards
Ronald
5

Anyone can help me please???

6 
long int debounce_time = 5; // some small number

if( buttonPressed && numberOfButtonPresses == 1 && ( millis() - startTime > debounce_time) ) { 
...

of course you can also 'hardware debounce' your switch with an RC lowpass filter.