This commit also adds a bit of version independence, in particular for
external commands. It also adds the LLVM version to the `tinygo version`
command, which might help while debugging.
Add a target for the Adafruit Circuit Playground Bluefruit, which is
based on the nRF52840. Adds the necessary code for the machine
package and the json and linker script files in the targets directory.
The machine package code is based on board_circuitplay_express.go,
with modifications made by consulting the wiring diagram on the
adafruit website here:
https://learn.adafruit.com/adafruit-circuit-playground-bluefruit/downloads
Also adds support to the uf2 conversion packacge to set the familyID
field. The Circuit Playground Bluefruit firmware rejects uf2 files
without the family id set to 0xADA52840 (and without the flag specifying
that the family id is present).
Compared to the already supported stm32f103xx "bluepill" board this:
- features 128 KiB flash memory size ("RB" suffix) instead of 64 KiB, see `targets/stm32f103rb.ld`
- has onboard ST-LINK/V2-1 programmer and debugger requiring different OpenOCD configuration file
- uses USART2 connected to ST-LINK/V2-1 debugger as virtual COM port over USB for `putchar()`
- has a user-accessible button besides the reset button
This provides several advantages. Among others:
* Much faster and hopefully more reliable.
* Good caching support to store LLVM builds.
* Building and testing of release-ready artifacts.
CircleCI is faster and has more features than Travis CI. Additionally,
based on the recent news, the future of Travis CI is rather uncertain.
Keep using Travis CI for macOS testing at the moment, as open source
projects will need to get special permission to use CircleCI for macOS
tests.
Support for channels is not complete. The following pieces are missing:
* Channels with values bigger than int. An int in TinyGo can always
contain at least a pointer, so pointers are okay to send.
* Buffered channels.
* The select statement.
