The "spacing" of "buffer structure" is confusing, use the "channel count"
instead.
Testing performed on nrf52840 feather:
Play stereo and mono, 8- and 16-bit, 8kHz RawSamples representing 333.33Hz
square waves.
Use both mono and stereo PWMAudioOut instances.
Scope the RC-filtered signal and use the scope's frequency
measurement function, verify the frequency is 333 or 334Hz in all tested
cases.
In the "stereo output" cases, verify both the L and R channels. Verify
the output amplitude is the same in both channels.
In the "stereo output" cases, run a second test where the L channel's
amplitude is attenuated 50%. Verify the output amplitude is correct
in each channel.
This adapts the "inline assembler" code from the UF2 bootloader, which
in turn is said to be adapted from the arduino neopixel library.
This requires the cache remain ON when using M0, and be turned OFF on M4
(determined by trial and error)
Testing performed on a Metro M4:
* measured timings using o'scope and found all values within
datasheet tolerance.
* Drove a string of 96 neopixels without visible glitches
* on-board neopixel worked
Testing performed on a Circuit Playground Express (M0):
* Color wheel code works on built-in neopixels
* Color wheel code works on 96 neopixel strip
As a bonus, this may have freed up a bit of flash on M0 targets. (2988 ->
3068 bytes free on Trinket M0)
Closes: #2297
Protocols are nice, but there is no way for C code to verify whether
a type's "protocol" structure actually implements some particular
protocol. As a result, you can pass an object that implements the
"vfs" protocol to one that expects the "stream" protocol, and the
opposite of awesomeness ensues.
This patch adds an OPTIONAL (but enabled by default) protocol identifier
as the first member of any protocol structure. This identifier is
simply a unique QSTR chosen by the protocol designer and used by each
protocol implementer. When checking for protocol support, instead of
just checking whether the object's type has a non-NULL protocol field,
use `mp_proto_get` which implements the protocol check when possible.
The existing protocols are now named:
protocol_framebuf
protocol_i2c
protocol_pin
protocol_stream
protocol_spi
protocol_vfs
(most of these are unused in CP and are just inherited from MP; vfs and
stream are definitely used though)
I did not find any crashing examples, but here's one to give a flavor of what
is improved, using `micropython_coverage`. Before the change,
the vfs "ioctl" protocol is invoked, and the result is not intelligible
as json (but it could have resulted in a hard fault, potentially):
>>> import uos, ujson
>>> u = uos.VfsPosix('/tmp')
>>> ujson.load(u)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: syntax error in JSON
After the change, the vfs object is correctly detected as not supporting
the stream protocol:
>>> ujson.load(p)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: stream operation not supported
.. inline-unit-growth was the same across all boards, and the highest
max-inline-insns-auto parameter was shared across 2 of 5 boards, so it's
worth a little work to follow the DRY principle
The sample width register was never set, so all samples were played
as though they were 16 bit.
After this change, 8-bit samples no longer produce audio on the MAX 98357A
BOB, because only 16-, 24-, and 32-bit samples are supported by the
hardware. This will be addressed by a future change to pad samples to
16 bits; see #2323 and the 98357A datasheet page 6.
The meaning of the "single channel" parameter is not well-documented,
but in fact it seems that "true" must be passed or else the returned
channel_count is always 1. This caused stereo samples to be played
incorrectly.
This caused two problems when playing unsigned samples:
* When an even number of samples were present, it "worked" but only
every other sample was copied into the output, changing the waveform
* When an odd number of samples were present, the copy continued beyond
the end of the buffers and caused a hard fault
If we put no samples into the buffer, then there is no last
sample to fill out hold_value with. (and, in fact, the expression such
as *(uint32_t*)(buffer-4) is outside an allocated region)
Detect this condition, and leave the prior value in place.
This improves clicks heard when pausing and resuming a waveform.
If you define MONITOR_BACKGROUND_TASK, then a physical output pin
(Metro M4 Express's "SCL" pin by default) will be set HIGH while in
the background task and LOW at other times
This code is shared by most parts, except where not all the #ifdefs
inside the tick function were present in all ports. This mostly would
have broken gamepad tick support on non-samd ports.
The "ms32" and "ms64" variants of the tick functions are introduced
because there is no 64-bit atomic read. Disabling interrupts avoids
a low probability bug where milliseconds could be off by ~49.5 days
once every ~49.5 days (2^32 ms).
Avoiding disabling interrupts when only the low 32 bits are needed is a minor
optimization.
Testing performed: on metro m4 express, USB still works and
time.monotonic_ns() still counts up
