`#define MOZZI_AUDIO_RATE 65536` not compatible with `Oscil` on some platform

[tomcombriat]

Setting Mozzi's audio rate to 65536 is not officially supported, but more and more people are using this rate these days as it can be seen in the forum and some of the issues/PR published here.

After the typo fixed in #306 , it seems that setting the rate that high leads to an error, at least on some platforms.

Test sketch

#include <MozziConfigValues.h>
#define MOZZI_AUDIO_RATE 65536
#include <Mozzi.h>

#include <Oscil.h> // oscillator template
#include <tables/sin2048_int8.h> // sine table for oscillator

// use: Oscil <table_size, update_rate> oscilName (wavetable), look in .h file of table #included above
Oscil <SIN2048_NUM_CELLS, MOZZI_AUDIO_RATE> aSin(SIN2048_DATA);


void setup(){
  startMozzi(); // start with default control rate of 64
}


void updateControl(){}

AudioOutput updateAudio(){
  return MonoOutput::from16Bit(0);
}

void loop(){
  audioHook(); // required here
}

Error message

/tmp/.arduinoIDE-unsaved2025621-60578-87yq4x.3gpop/Control_Gain/Control_Gain.ino:9:43: error: narrowing conversion of '65536' from 'int' to 'short unsigned int' [-Wnarrowing]
    9 | Oscil <SIN2048_NUM_CELLS, MOZZI_AUDIO_RATE> aSin(SIN2048_DATA);
      |                                           ^
/tmp/.arduinoIDE-unsaved2025621-60578-87yq4x.3gpop/Control_Gain/Control_Gain.ino:9:50: error: invalid conversion from 'const int8_t*' {aka 'const signed char*'} to 'int' [-fpermissive]
    9 | Oscil <SIN2048_NUM_CELLS, MOZZI_AUDIO_RATE> aSin(SIN2048_DATA);
      |                                                  ^~~~~~~~~~~~
      |                                                  |
      |                                                  const int8_t* {aka const signed char*}

Platform tested

Platform	Compiles	Run
RP2040	No	No
ESP32	No	No
AVR	Yes	?

[tomcombriat]

I guess the easy solution would be to change the second template parameter of Oscil to uint32_t instead of uint16_t. As all the computation involving the rate are done in 32bits in Oscil I would guess this should not have any impact on performances, but I might not have the full picture.

[pelandrun]

Add -Wno-narrowing to the compiler options

compiler.warning_flags=-Werror=return-type -Wno-psabi -Wno-narrowing
compiler.warning_flags.none=-Werror=return-type -Wno-psabi -Wno-narrowing
compiler.warning_flags.default=-Werror=return-type -Wno-psabi -Wno-narrowing
compiler.warning_flags.more=-Wall -Werror=return-type -Wno-ignored-qualifiers -Wno-psabi -Wno-narrowing
compiler.warning_flags.all=-Wall -Wextra -Werror=return-type -Wno-ignored-qualifiers -Wno-psabi -Wno-unused-parameter -Wno-missing-field-initializers -Wno-narrowing

[tomcombriat]

@pelandrun Thanks for this! This explains why it does work on some platforms and not on some as they have different toolchain (and different compiler options).
This might be a bit too much to ask a user to do, I will try to implement the fix discussed above and benchmark how much this has an impact.