This is not very useful in itself, but makes it possible to detect this
address in the output. See the next commit.
This adds around 50 bytes to each binary (except for AVR and wasm). This
is unfortunate, but I think this feature is quite useful still.
A future enhancement might be to create a build tag for extended panic
information that's not set by default.
Multisampling/averaging (using the Samples configuration property) was
returning incorrect values. When I investigated this, I found that the
samd51 gives erratic values when using multisampling together with fewer
than 16 bits resolution.
I fixed this by forcing 16 bit resolution when multisampling, and
adjusting the output to account for multisampling.
Found while reading the battery value on a pybadge, which gave
non-sensible values with Samples set to a value larger than 1.
This improves slightly. It also is some groundwork for better DMA
support in TinyGo in the future.
I'm not entirely sure why it improves performance (in theory the old
code should already saturate the SPI bus) but it does, so 🤷
The SPI frequency was rounded up, not rounded down. This meant that if
you wanted to configure 15MHz for example, it would pick the next
available frequency (24MHz). That's unsafe, the safe option is to round
down and the SPI support for most other chips also rounds down for this
reason.
In addition, I've improved SPI clock selection so that it will pick the
best clock of the two, widening the available frequencies. See the
comments in the patch for details.
As discussed on Slack, I believe this property does more harm than good:
* I don't think it's used anywhere. None of the drivers use it.
* It is not fully implemented. While values <= 8 might work fine,
values larger than 8 result in extra zero bits (instead of anything
sensible).
* Worse, it doesn't return an error when it's out of range. This is
not an optional property: if the SPI peripheral doesn't support a
particular number of bits, it should return an error instead of
silently limiting the number of bits. This will be confusing to
users.
Therefore, I propose we drop it. Maybe there are good uses for it
(perhaps for displays that use big endian 16-bit values?), but without a
good use case like a driver in tinygo.org/x/drivers, I think it's more
trouble than it's worth.
