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doc/doxygen: add creating boards doc

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@ -764,6 +764,7 @@ INPUT = ../../doc.txt \
src/mainpage.md \ src/mainpage.md \
src/creating-modules.md \ src/creating-modules.md \
src/creating-an-application.md \ src/creating-an-application.md \
src/porting-boards.md \
src/driver-guide.md \ src/driver-guide.md \
src/getting-started.md \ src/getting-started.md \
../../tests/README.md \ ../../tests/README.md \

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doc/doxygen/src/mainpage.md
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@ -239,6 +239,7 @@ Further information {#further-information}
=================== ===================
- @ref getting-started - @ref getting-started
- @ref creating-an-application - @ref creating-an-application
- @ref porting-boards
- @ref creating-modules - @ref creating-modules
- @ref advanced-build-system-tricks - @ref advanced-build-system-tricks

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@ -0,0 +1,296 @@
Porting boards {#porting-boards}
================
At some point you might need to port a new `BOARD` to `RIOT`, either because
that specific development board is not yet supported or because you have a
custom `BOARD` for your project.
If you want to port a `BOARD` to `RIOT` you have two choices: doing it
inside of `RIOTBASE` or outside. In either case the file structure
is basically the same and moving from one to another is easy.
This guide details the generic structure you need to add a new `BOARD`
to `RIOT`, the different files as well as their functionality.
@note We assume here that your `CPU` and `CPU_MODEL` is already supported
in `RIOT` so no peripheral or cpu implementation is needed.
# General structure {#general-structure}
Like @ref creating-an-application "applications" or @ref creating-modules
"modules", boards consist on a directory containing source files and
makefiles. Usually a `BOARD` directory has the following structure
```
board-foo/
|----dist/
|----scripts
|----board.c
|----doc.txt
|----include/
|----periph_conf.h
|----board.h
|----gpio_params.h
|----Makefile
|----Makefile.dep
|----Makefile.features
|----Makefile.include
```
## Source files {#board-source-files}
Header files in `board-foo/include` define physical mappings or
configurations. e.g:
- `periph_conf.h`: defines configurations and mappings for peripherals as well
as clock configurations.
- `board.h`: holds board specific definitions or mappings, for example LEDs,
buttons. It might as well override default drivers parameters (e.g.: assigning
specific pin connections to a LCD screen, radio, etc.). Some boards might also
define optimized `XTIMER_%` values (e.g. @ref XTIMER_BACKOFF).
- `gpio_params.h`: if the board supports @ref drivers_saul "SAUL" then its
@ref saul_gpio_params_t is defined here.
- other: other specific headers needed by one `BOARD`
@note Header files do not need to be defined in `include/`, but if defined
somewhere else then they must be added to the include path. In
`Makefile.include`: `INCLUDES += -I<some>/<directory>/<path>`
Board initialization functions are defined in `board.c`. This file must at
least define a `board_init()` function that is called at startup. This
function initializes the `CPU` by calling`cpu_init()` among others.
```c
void board_init(void)
{
/* initialize the CPU core */
cpu_init();
/* initialize GPIO or others... */
...
}
```
## Makefiles
### Makefile {#Makefile}
A board's Makefile just needs to include `Makefile.base` in the RIOT
repository and define the `MODULE` as `board` (see @ref creating-modules
"modules" for more details)
```mk
MODULE = board
include $(RIOTBASE)/Makefile.base
```
### Makefile.dep {#makefile-dep}
Dependencies on other `MODULES` or `FEATURES` can be defined here. This might
specify `MODULES` or dependencies that need to be pulled under specific
configurations. e.g.: if your board has a sx1276 lora chip:
```mk
ifneq (,$(filter netdev_default,$(USEMODULE)))
USEMODULE += sx1276
endif
```
@note `Makefile.dep` is processed only once so you have to take care of adding
the dependency block for your board *before* its dependencies pull in their own
dependencies.
### Makefile.features {#makefile-features}
This file defines all the features provided by the BOARD. These features
might also need to be supported by the `CPU`. Here, define the `CPU` and
`CPU_MODEL` (see @ref build-system-basics "build system basics" for more details
on these variables).
e.g.:
```mk
CPU = foo
CPU_MODEL = foobar
# Put defined MCU peripherals here (in alphabetical order)
FEATURES_PROVIDED += periph_i2c
FEATURES_PROVIDED += periph_spi
FEATURES_PROVIDED += periph_uart
```
### Makefile.include {#makefile-include}
This file contains BSP or toolchain configurations for the `BOARD`. It
should at least define the configuration needed for flashing (i.e. a
programmer) as well as the serial configuration (if one is available).
e.g.:
```mk
# Define the default port depending on the host OS
PORT_LINUX ?= /dev/ttyUSB0
PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.usbserial*)))
# setup serial terminal
include $(RIOTMAKE)/tools/serial.inc.mk
# this board uses openocd
include $(RIOTMAKE)/tools/openocd.inc.mk
```
## doc.txt {#board-doc}
Although not explicitly needed, if upstreamed and as a general good
practice, this file holds all `BOARD` documentation. This can include
datasheet reference, documentation on how to flash, etc.
The documentation must be under the proper doxygen group, you can compile the
documentation by calling `make doc` and then open the generated html file on
any browser.
```md
/**
@defgroup boards_foo FooBoard
@ingroup boards
@brief Support for the foo board
@author FooName BarName <foo.bar@baz.com>
### User Interface
....
### Using UART
...
### Flashing the device
...
*/
```
# Using Common code {#common-board-code}
To avoid code duplication, common code across boards has been grouped in
`boards/common`. e.g. `BOARD`s based on the same cpu (`boards/common/nrf52`) or
`BOARD`s having the same layout `boards/common/nucleo64`.
In the case of source files this means some functions like `board_init` can be
already defined in the common code. Unless having specific configurations or
initialization you might not need a `board.c` or `board.h`. Another common use
case is common peripheral configurations:
```diff
-\#include "cfg_timer_tim5.h"
+/**
+ * @name Timer configuration
+ * @{
+ */
+static const timer_conf_t timer_config[] = {
+ {
+ .dev = TIM5,
+ .max = 0xffffffff,
+ .rcc_mask = RCC_APB1ENR_TIM5EN,
+ .bus = APB1,
+ .irqn = TIM5_IRQn
+ }
+};
+
+#define TIMER_0_ISR isr_tim5
+
+#define TIMER_NUMOF ARRAY_SIZE(timer_config)
+/** @} */
```
If you want to use common makefiles, include them at the end of the specific
`Makefile`, e.g. for a `Makefile.features`:
```mk
CPU = foo
CPU_MODEL = foobar
# Put defined MCU peripherals here (in alphabetical order)
FEATURES_PROVIDED += periph_i2c
FEATURES_PROVIDED += periph_spi
FEATURES_PROVIDED += periph_uart
include $(RIOTBOARD)/common/foo_common/Makefile.features
```
# Boards outside of RIOTBASE {#boards-outside-of-riotbase}
All `BOARD`s in RIOT reside in `RIOTBOARD` (`RIOTBOARD` being a make variable
set to `$(RIOTBOARD)/boards`).
If one wants to use a `BOARD` outside of `RIOTBOARD`, the way to go is setting
the `BOARDSDIR` variable to the path to the directory containing your external
boards, e.g.: `BOARDSDIR=/home/external-boards/` (this would commonly be done
in your application `Makefile` or your environment).
```
/home/
|----RIOT/
|---- ...
|----external-boards/
|----board-foo/
|----dist/
|----scripts
|----board.c
|----doc.txt
|----include/
|----periph_conf.h
|----board.h
|----gpio_params.h
|----Makefile
|----Makefile.dep
|----Makefile.features
|----Makefile.include
```
If the external `BOARD` is very similar to a `BOARD` already present in
`RIOTBOARD`, the external `BOARD` (`board-foo`) can inherit from that
parent `BOARD` (e.g: `foo-parent`).
In this case some special considerations must be taken with the makefiles:
- `Makefile`
- `MODULE` cannot be `board`: `foo-parent` will already define
`MODULE = board`, so use any other name, lets say `MODULE = board-foo`.
- Include the location of the parent `BOARD` to inherit from (if there is
one):
```mk
DIRS += $(RIOTBOARD)/foo-parent
```
- `Makefile.include`
- duplicate the include done by `$(RIOTBASE)/Makefile.include` to also
include the parent board header. e.g: if inheriting from `foo-parent`
``INCLUDES += $(addprefix -I,$(wildcard $(RIOTBOARD)/foo-parent/include))`
- `Makefile.dep`: `board` is added by default to `USEMODULE` but since
`board-foo` is used for this `BOARD`, it must be explicitly included by adding
`USEMODULE += board-foo`.
- Then simply include in each `Makefile.*` the corresponding parent `BOARD`
`Makefile.*`, just as it is done for common `BOARD` code (as explained in
@ref common-board-code). e.g:
`include $(RIOTBOARD)/foo-parent/Makefile.*include*`
An example can be found in
[`tests/external_board_native`](https://github.com/RIOT-OS/RIOT/tree/master/tests/external_board_native`)
# Tools {#boards-tools}
Some scripts and tools available to ease `BOARD` porting and testing:
- Run `dist/tools/insufficient_memory/add_insufficient_memory_board.sh <board>`
if your board has little memory. This updates the `Makefile.ci` lists to
exclude the `BOARD` from automated compile-tests of applications that do
not fit on the `BOARD`s `CPU`.
- Run `dist/tools/compile_and_test_for_board/compile_and_test_for_board.py . <board> --with-test-only`
to run all automated tests on the new board.