This evolves the API from 2.x (and breaks it). Playback devices are now
separate from the samples themselves. This allows for greater playback
flexibility. Two sample sources are audioio.RawSample and audioio.WaveFile.
They can both be mono or stereo. They can be output to audioio.AudioOut or
audiobusio.I2SOut.
Internally, the dma tracking has changed from a TC counting block transfers
to an interrupt generated by the block event sent to the EVSYS. This reduces
the overhead of each DMA transfer so multiple can occure without using up TCs.
Fixes#652. Fixes#522. Huge progress on #263
1. UART: ported to ASF4. Allow rx-only and tx-only. Add .baudrate r/w property.
2. Make NeoPixel timing deterministic by turning off caches during NeoPixel writes.
3. Incorporate asf4 updates:
a. async USART driver
b. bringing Atmel START configuration closer to what we use
c. Clock initialization order now specified by CIRCUITPY_GCLK_INIT_1ST and _LAST.
4. supervisor/port.c: Move commented-out clock-test pin setting to correct location.
This introduces a new spi_flash_api.h that works for both SPI and
QSPI. The previous spi_flash functions are now called external_flash
to minimize confusion.
Also, fixed pin mappings for rev B Metro M4:
swap PA12 and PA13 on SPI 2x3 header
swap A3 and A5
Comment out all frozen modules in CPX again to make room while waiting
for SPI flash.
* Added asf4_conf/samd*/hpl_sercom_config.h
* Adjusted clocks in peripheral_clk_config.h.
* Put some frozen libs back in CPX for testing.
* Implement common-hal I2C
* Add samd*_peripherals.h in parallel with samd*_pins.h for common
functions and data.
* Store SERCOM index in pins table for convenience.
* Canonicalize some #include guard names in various .h files.
simpler reset of SERCOMs; remove unused routine
* Introduce a python script to generate the USB descriptor instead of
a bunch of C macros. In the future, we can use this dynamically in
CircuitPython.
* Add support for detecting read-only mass storage mounts.
Fixes#377
* Revert "Read serial input as a background task so we can check for the interrupt character."
This reverts commit 046092e8a2.
* Revert "Check INTERNAL_LIBM make flag in a safer way."
This reverts commit 2b80add22f.
