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[Reply #15 on:]

Ohhh, very nice! I need to download a library update, right? Thanks again for such hard work! 

[Reply #16 on:]

No, I have not changed the library yet. Maybe I will do it later after documenting it better - you only need the new batch file. We should try level-shifters or buffers (anything that is very cheap and easy available) to improve the sound (should be placed between Arduino outputs 9/10 and resistor stuff. 

[Reply #17 on:]

I haven't messed out with the library source yet, but do you think it would be possible to get a more instant playback and re-play by setting an initial file, and just have it play, and re-play when requested? This way I could use this to playback long drum sounds. (crashes and cymbals) I need this for a small project I'm doing. ;-) Maybe an option to open the file and have it used until said to open a new one? Also, an option to re-start the file, even if its not done yet, for when you play a drum sound, you are in the middle, but needs to re-trigger the sound.

[Reply #18 on:]

I wonder one thing, would it be possible to handle 16-bit stereo files? Using 4 x pwm outputs for 2 x 16-bit hybrid dacs? What's the limitation them? I see that a 5Mb SD Card can handle it without problems, is the bottle-neck the SPI or the ATmega itself? Maybe running at 20Mhz would help? Just wondering, as it would be KILLER to be able to play 16-bit stereo files.

[Reply #19 on:]

In any event, it should be possible to handle mono 16-bit 31khz .WAV files now, right? I know how to handle WAV files, so I will see if I can be of any help on this...

[Reply #20 on:]

With this I got a perfect loop:

Code:

while (1)
  {
    // Start playback
    SdPlay.play();
 
    // Let the worker work until playback is finished
    while(!SdPlay.isStopped()) {
      SdPlay.worker();
    }
  }

[Reply #21 on:]

I just tested the 16-bit hybrid dac with your code, as explained, and I love it, great quality!  I hear a strange buzz on the background, is that the PWM? I'm using an external power-adapter and running the ATmega328 at 3.3V, to keep the SD Card connections simpler.

I haven't done your full 16-bit dac specs, I used a 256k and just one 1k resistor, so now I will try the way you did, to see if the buzz goes away. ;-)

Thank you so much for the hard work on this lib!! 

[Reply #22 on:]

The project I'm working requires 4 loops to be played, not at the same time, but with the option to go from one to another. So I wonder if I could do some sort of pre-buffering for all 4 files, in a way I could just go from one to another with min. gaps?

[Reply #23 on:]

Ok, I found the buzz sound problem. It was the 3.3 V thingy. Now I'm running at 5V and using a proper SD Card adapter for Arduino (it has all the voltage converters) and it sounds GREAT! Thanks again! 

[Reply #24 on:]

Darn, the buzzing sound is still there, its from the PWM output. But its much lower now, compared to before.

[Reply #25 on:]

Ok, assuming you can also hear the buzzing sound there, how about using 2 timers? One for the DAC and another one for the sample-rate. For instance, Timer1, which you already use now for both sample-out and sample-buffering, you could leave just for the DAC and setup for 9 bits, so the frequency of PWM is much faster. Then another timer for the rest, lets say, Timer2.

I will check the code when possible to see if I could just hack it and hear the result.

At least on my 6-voice sampler I did it with a higher frequency PWM using Timer1 and there's no buzzing sound. Unless my chip is faulty. I will test my 6-voice sampler on this same setup, just in case. ;-) Here's the link: https://github.com/Beat707/BeatVox

Again, thanks for doing this lib, I'm really loving it! 

[Reply #26 on:]

Darn, I can't figure out this buzzing sound, no idea where its coming from, maybe the SPI interface? (doubt that) What I see you did different from my 6-voice thingy, is that you take a bit to update the PWM outputs, I do it first-thing, from a 2-byte buffer, maybe that could help? I will try that. ;-)

[Reply #27 on:]

Darn thing, it does sound like the SPI. Here's a simple test.

Code:

uint8_t bufferL = 80, bufferR = 80;
 
void SdPlayClass::interrupt(void)
{
//SSDA_OC1L = bufferL;
//SSDA_OC2L = bufferR;

SSDA_OC1L = 255;
SSDA_OC2L = 255;

  uint8_t  flags = _flags;  // local copy for faster access
 
...

Code:

void setup()
{
  SdPlay.init(SSDA_MODE_HALFRATE | SSDA_MODE_STEREO);
  SdPlay.setFile("Loop5.a16"); // 16-bit mono file - half rate
   
   while (1)
   {
     SdPlay.play(); while(!SdPlay.isStopped()) { SdPlay.worker(); }
   
     pinMode(SCK, INPUT);
     digitalWrite(SCK, HIGH);
     delay(1000);
     pinMode(SCK, OUTPUT);   
   }
...

I can hear the buzzing sound, once the loop is done, it will pause for 1 second without the buzz sound.

Unless I'm doing this test wrong. ;-)

[Reply #28 on:]

Well, it does seem to be the SPI clock leaking somewhere, not sure what to do... any ideas? 

[Reply #29 on:]

Hi,

the buzzing sound can come from anything on the Arduino or stuff connected to it. I don't think that you can get rid of it just by optimizing the software - increasing sample rate will not change things. The quality out of the PWM is already superior, but get's damaged by the noise on the supply lines.
Therefore as I proposed before try to use something that "isolates" the digital PWM lines from power source. Use a buffer or a level shifter. Then filter the supply for that level shifter very thouroughly  using an own linear regulator or at least a serial resistor with a capacitor to gnd between VCC-digital and VCC-analog.

Regarding 4channel mode: If I translate the interrupt function to assembler then it should be possible to have enough computing power for stereo 16 bit playback...

Regarding pre-load: The function setFile stores internally something about the file in a small structure. By using that struct it should be possible to playback any file with very little latency. Maybe I will add this feature later to the library.