For anything time sensitive don't rely on framerate but instead use millis()

As for the rest of it: you've confused me a bit too.  I'd guess you should be fine loading it all into memory: I can't imagine it's a very big file...  However; if you're loading the contents of the file in setup then why do you need to 'read' contents from it every second.  Presumably you mean you want to move a step forward through the data each second?

If that's the case and assuming you're loadng the content of the file into an array you can set a global variable that represents the index of the array and increase this every second by using millis():

1. String myArray[];
2. int arrayIndex;
3. int startTime;
4. 
   
5. void setup() {
6.       size(400,400);
7.       // populate array
8.       myArray = loadStrings("myTextFile.txt");
   
9.       startTime = millis();
10. }
11. 
    
12. void draw() {
13.       println(myArray[arrayIndex]);
14.       if(millis() >= startTime + 1000){
15.             arrayIndex ++;
16.             // reset start time
17.             startTime = millis();
18.       }
19. }

Sorry if i was confusing,

Here's a more intelligible version of my question (i hope so).

I've recorded a signal in a CSV file (not that big, u're right). The signal was recorded during 1 second at 64Hz.
So my file contain 64 entry each 15.625ms.
Each row of the CSV file looks like Time, Voltage with :

• Time -> the time ellapsed since started recording
• Voltage -> the signal value at Time T

Now, i want to playback the signal at exactly the same rate it was recorded.
So if the sampling rate is 64hz i need to read the array entry each 15.625ms.

That is if i got a row like 0.90625, -0.845175 i need the -.845175 value to be read at 906.25ms since the sketch is started.
The problem is i'm not sure i can read values with that precision or even higher (because i do have other recording at 512hz).

To resume, the content of the file should be read in exact timing at which it was recorded.
So after one second the sketch is started, the array was totally read.

Many thanks for your answer btw and sorry again for the confusion

S.

I understood your intenstion, but i would be interested why do you need it to be read at the exact time. Not sure but i would say you wont recognize it anyway. Why is it so important.

I understood your intenstion, but i would be interested why do you need it to be read at the exact time. Not sure but i would say you wont recognize it anyway. Why is it so important.

Because the values are extracted from an ECG simulator.
I wanna loop the array at the same exact time to reproduce the heart BPM which was simulated.
It's just a test framework but afterwards the intention is to rely people to the sketch with real ECG in realtime.
That's why i try to read the file at the same frequency.

ah ok, so the sketch is looping through the file every second?

anyway, pretty hard tastk. not sure if it is possible at all.
If you set the frameRate to 256 to get as many frames per second. you still get this result as frame Rate :


258.3869
257.75513
256.9887
256.31744
255.65779
263.81705
262.25693
261.17062
254.75963
263.71704


so not as precisely as you wish

ah ok, so the sketch is looping through the file every second?

Exactly,  but i redesigned the idea of the program. I fear my approach was wrong and stupid. As the signal is recorded at a fixed samplerate i don't need to extract the time values from the file.

 Instead i just need to read the voltage value at the time interval given by the sampling frequency. So if it's 64hz that gives 15,625ms.

Now the problem isn't to read the values at the same time from the file but how to read the values each 15,625ms.

If i'm getting the right idea, setting the framerate to 64 fps should do call draw every ~15/16ms so should reproduce a close behavior or am i wrong ?

For anything time sensitive don't rely on framerate but instead use millis()

You'll never get the level of accuracy you want if you rely on the frameRate.  Even millis() may not be accurate enough for your purposes; but I do recall someone suggesting a Java solution that offered greater accuracy; and possibly running the timing on a separate thread...

TBH this question is something of a FAQ - I'd suggest you search the old forum.

You'll never get the level of accuracy you want if you rely on the frameRate.  Even millis() may not be accurate enough for your purposes; but I do recall someone suggesting a Java solution that offered greater accuracy; and possibly running the timing on a separate thread...

TBH this question is something of a FAQ - I'd suggest you search the old forum

I totally agree with your point of view, many thanks for that answer. I'll dig a search in the old forum and post the link to solve that issue as soon as i find the correct answer. I'll let you know. Thanks a lot again.