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Improved AudioEffectDelayExternal #433

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h4yn0nnym0u5e
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@h4yn0nnym0u5e h4yn0nnym0u5e commented Apr 1, 2022

  • implements a few more options for memory type
  • breaks out the memory management into AudioExtMem base class so (future) audio objects can share resources
  • documentation added

Subsequent improvements

  • resilience against SPI initialisation issues
  • speed improvement for SPI-based memory on Teensy 4.x
  • update() code simplified by improvements to AudioExtMem class

@PaulStoffregen
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oh no, looks like a conflict with another recent commit

… feature/AudioEffectDelayExternal

# Resolved Conflicts:
#	gui/index.html
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Think I fixed it - there was a previous PR which corrected a copy-pasta error to do with freeing up delay memory, which hadn't propagated into this one. Or something...

Only briefly tested with a partially populated 64MB memory board (see https://forum.pjrc.com/threads/29276-Limits-of-delay-effect-in-audio-library?p=320254&viewfull=1#post320254)

There was an issue with the undefined initialization order of the delay object(s) compared to the supporting SPI object. This wasn't apparent during previous testing, and may be a result of updates to the C++ compiler. We now "pre-initialise" the object, and only finish configuring SPI memory when the first call to delay() is made. Search for "C++ static initialization order fiasco" for more detail than you want.

Note that for huge amounts of SPI RAM the initialisation time can be quite significant, as the whole block is zeroed out at the start to ensure silence is output, before the first real samples are input to the memory.
@h4yn0nnym0u5e
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Note that 0544053 fixes a pretty serious bug that rendered this object almost completely unusable, at least on my Windows 10 / Arduino 1.8.19 system.

@h4yn0nnym0u5e
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8ed2b49 reverts by default to the "old scheme" of initialising SPI memory at object construction time, since a fix has been done to the SPI library. Deferred initialisation is still available by setting a third constructor parameter to false (if not supplied it defaults to true): this may be of use to users who have only partially updated their libraries.

See https://forum.pjrc.com/threads/73154-Teensy-4-1-does-not-boot-when-invoking-SPI-from-external-class and PaulStoffregen/SPI@1904fb5

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Brought into sync with Teensyduino 1.60 beta 1 updates

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