Porting teensyOsc to 4.1

[dlawle]

Howdy!

I’m working on porting your teensyOsc to 4.1. So far so good aside from a single problem I can’t quite wrap my head around and I was wondering if you had any insight.

I’m using a pcm5102a for the dac output and have confirmed that it’s functioning as it should via some low level audio scripts as well as some example hardware tests.

When I load the modified code (only thing changed was the removal of the dac to an i2s audio object) and removed the dac.analogReference(EXTERNAL); line. The output comes through just fine, but the audio is very “muddy” (almost like there’s cloudy pops in the output).

I’ve tried different pots, different ports etc but can’t seem to figure out the issue. I loaded the serial pot reads onto a teensy lc and can confirm that the pot output is within line/expectation (0.0-0.25).

many ideas here?

[dlawle]

Small update. Placing a delay in loop() seems to fix the quality, but obviously the audio is stuttered by the delay.

I’ve read about analog reads causing noise, so this may be the root cause. Still investigating!

[otem]

Hmm. I’ve actually rebuilt this with a teensy 4 and changed it quite a bit. I think I’m also using the 5102a on this new one. Sounds like it indeed might be a noisy analog read issue. I’d say try removing all the analog reads to test and see if that helps.

[dlawle]

I am planning on trying that as well, I just need to find a good frequency to set everything to so that I can tell audibly (out of the box it’s pretty low!)

Was also reading about audioNoInterrupts(). In your latest port to the 4, did you change the no interrupts location?

Also, fwiw I am testing the output without running it through an opamp, but I don’t think that would cause many issues.

If it’s ok with you, may I fork your repo and post some of the working code there?

[dlawle]

Feel like an absolute numpty. the issue was with the CV pins - My I2s DAC is running on one of the CV pins. So I changed that as follows:

int pitchCVPins[3] = {A15,A14,A16};

And we're good to go,

still see a little noise on the filter pot (currently A10 or pin 24) need to try moving that around.