Patching a package creates a new HEAD of the package repository. Using `git describe --tag` to generate a version string used for the ESP8266 bootloader therefore generates a different version string for each new compilation, which in turn results in different hash values of the binaries for the same application in subsequent compilations in CI. To use the commit in `git describe --tag` for commit used by the package, the commit has to specified in the command.
We had four versions of pre-built bootloaders for the esp8266 with
different settings of logging and color logging. These bootloaders were
manually built from the SDK and shipped with RIOT-OS source code.
However there are more settings that affect the bootloader build that
are relevant to the app or final board that uses this bootloader. In
particular, flash size and flash speed is important for the bootloader
to be able to load an app from a large partition table at the fastest
speed supported by the board layout and flash chip.
Another example is the UART baudrate of the logging output from the
bootloader. The boot ROM will normally start at a baud rate of 74880
(depending on the crystal installed), so it might make sense to keep
the UART output at the same speed so we can debug boot modes and
bootloader with the same terminal.
This patch builds the bootloader.bin file from the ESP8266 SDK source
code. The code is built as a module (esp8266_bootloader) which at the
moment doesn't generate any object code for the application and only
produces a bootloader.bin file set to the BOOTLOADER_BIN make variable
for the esptool.inc.mk to flash.
The code needs to be compiled and linked with custom rules defined in
the module's Makefile since the bootloader.bin is its own separate
application.
The `BOOTLOADER_BIN` variable is changed from a path relative to the
`$(RIOTCPU)/$(CPU)/bin/` directory to be full path. This makes it easier
for applications or board to provide their own bootloader binary if
needed.
As a result of building the bootloader from source we fixed the issue of
having a large partition table. Fixes#16402.
The shared `build-libs` directory needs to be available for
modules/packages that depend on the SDK before that package
is eventually compiled.
Packages are downloaded, patched and prepared before any
module is compiled. By adding the directory creation and
header as a dependency of `PKG_PREPARE` we make sure the
rule is run before compilation starts.
Some small changes to use a common document and naming style for all ESP SDK packages. The @defgroup command should start with the name to keep alphabetical order in doc as well as Kconfig
RIOT-OS uses part of Espressif ESP8266 RTOS SDK to build support for
this CPU. The SDK includes some vendor-provided closed source
pre-compiled libraries that we need to modify to adapt to RIOT-OS
usage. This library modifications was done once and uploaded to a fork
of the vendor repository and was provided as an environment variable.
This patch changes two things:
1. It installs the SDK as a RIOT PKG from the new pkg/esp8266_sdk
directory instead of requiring the user to download it separately.
2. It performs the library modifications (symbol renames) on the pkg
Makefile removing the need to use a fork with the modifications applied
and simplifying the SDK update and future modifications.
This change sets the SDK package version (git SHA) to the same one that
our fork was using as a parent in the vendor repository, meaning that
the output libraries are exactly the same as before.
Tested with
```
ESP8266_RTOS_SDK_DIR=/dev/null USEMODULE=esp_log_startup make -C tests/shell BOARD=esp8266-esp-12x flash
```
and verified that the program works. The boot message now includes:
```
ESP8266-RTOS-SDK Version v3.1-51-g913a06a9
```
confirming the SDK version used.
`/dev/null` in the test is just to make sure that no evaluation of
`ESP8266_RTOS_SDK_DIR` in make is affected by the environment variable
value which would be set to the SDK for people who followed the set up
instructions before this change.
Tested the checkout size:
```bash
$ du -hs build/pkg/esp8266_sdk/
124M build/pkg/esp8266_sdk/
```
