play_tone() not working

[caternuson]

Confirmed. See here for more info and sample code:
https://forums.adafruit.com/viewtopic.php?f=58&t=140985

[caternuson]

For completeness, here's firmware I tested with:

Adafruit CircuitPython 3.0.1 on 2018-08-21; Adafruit CircuitPlayground Express with samd21g18 
>>> from adafruit_circuitplayground.express import cpx
>>> cpx.play_tone(330, 1)
>>> cpx.play_tone(660, 1)
>>>

[ladyada]

huh! ok odd, @kattni wanna take a look in the next day or so?

[sommersoft]

I can third this with 3.0.2. Used...

>>> for i in range(50):
...     tone = 300 + (i * 10)
...     print("Tone:", tone)
...     cpx.play_tone(tone, 0.5)
...

… which has a noticeable droop in the ~540Hz to ~690Hz range.

Additionally, I ran this with a factory fresh CPX with 2.2.0. The tones increase accordingly with above code. May need to debug audioio.AudioOut and/or audioio.RawSample.

[caternuson]

Agree, I think it's going to be something lower level than CPX. I can recreate with this:

import array
import math
import time

import board
import digitalio
import audioio

speaker_enable = digitalio.DigitalInOut(board.SPEAKER_ENABLE)

# Generator thing
def sine_sample(length):
    tone_volume = (2 ** 15) - 1
    shift = 2 ** 15
    for i in range(length):
        yield int(tone_volume * math.sin(2*math.pi*(i / length)) + shift)

# Generate the sample
length = 100
sine_wave = array.array("H", sine_sample(length))
sample = audioio.AudioOut(board.SPEAKER)
sine_wave_sample = audioio.RawSample(sine_wave)

# Play tone
frequency = 330
sample_rate = int(len(sine_wave) * frequency)
speaker_enable = True
sine_wave_sample.sample_rate = sample_rate
sample.play(sine_wave_sample, loop=True)
time.sleep(1)
sample.stop()
sample.deinit()
speaker_enable = False

[ladyada]

ooooh ok maybe this is a @tannewt @dhalbert level issue. (i thought it was just a bug in the cpx library)
will re-assign!

[tannewt]

I've opened adafruit/circuitpython#1196 to continue this investigation deeper. I'll also take a quick look now. Thanks!

[tannewt]

This is actually an issue with both.

The limit of the DAC is 350ksps which we weren't doing because the input clock was too slow. With the fix for adafruit/circuitpython#1196 660hz will work.

However, this library will start to crash when play_tones frequency is over 3500 ( * 100 is 350ksps) because it is now checked correctly.

So, I'm reopening this as well. The sample length should be reduced when the frequency is more than 3500 in order to keep the sample rate below the limit.

[caternuson]

The sample length should be reduced when the frequency is more than 3500 in order to keep the sample rate below the limit.

Take it you mean this needs to be done here in this lib? Instead of hardwired length of 100?

@ladyada should this be re-re-assigned?