Custom targets

[JohnK1987]

Hello,

what is a Custom target for MbedCE?
For example Bluephill or Blackpill are real custom targets? Technically they are unofficial dev boards what can be bought.
From my point of view the Custom board can be a board what I will made for myself or for my own product. But when I make a dev board based on a popular MCU and will be available in a shop, for example like Blackpill... what is Custom about it? In the context of ARM Mbed it is clear - no official maintainer or Mbed partner for the dev board = it is up to community = Custom board.

@multiplemonomials

BR, Jan

[multiplemonomials]

I'd say that custom target simply means that the target isn't included in the base Mbed OS source distribution, but is supported by a 3rd party package. At RPL, we generally created a custom target for each of our own boards (I confess that the new custom target support is motivated by our own internal needs).

Since Mbed CE is up to the community by definition, I think there's no problem with people contributing their own boards to the OS so long as those boards are actually a real product that people can get. So I'd welcome an MR to add an "official" blackpill target, so long as there is appropriate documentation for the target.

[multiplemonomials]

If you are using a custom target you do have to set this variable, it's used in CMake here: https://github.com/mbed-ce/mbed-os/blob/master/tools/cmake/mbed_generate_configuration.cmake#L10C4-L10C29

[lefebvresam]

That's strange. I put it in comment and it's all just working:

sam@elitebook-845:~/git/hmc20_ce_test$ sh build.sh -f
Generate build folder for target 'HMC20' with profile 'develop'
-- Mbed: Loading default upload method configuration from /home/sam/git/hmc20_ce_test/HMC20/HMC20.cmake
-- Mbed: Not building any Mbed OS tests.
-- Mbed: Code upload and debugging enabled via upload method STLINK
-- Mbed: No IDE detected, will generate configurations for command-line debugging (e.g. ninja gdbserver, then ninja debug-SomeProgram)
-- Configuring done (0.2s)
-- Generating done (0.1s)
-- Build files have been written to: /home/sam/git/hmc20_ce_test/build/develop
Build the code for target 'HMC20' with profile 'develop'
[1/1] Linking CXX executable source/hmc20.elf
-- built: /home/sam/git/hmc20_ce_test/build/develop/source/hmc20.bin
-- built: /home/sam/git/hmc20_ce_test/build/develop/source/hmc20.hex
| Module             |      .text |    .data |      .bss |
|--------------------|------------|----------|-----------|
| [fill]             |    112(+0) |   12(+0) |    39(+0) |
| [lib]/c.a          |  53016(+0) | 1808(+0) |   414(+0) |
| [lib]/gcc.a        |   3388(+0) |    0(+0) |     0(+0) |
| [lib]/misc         |    268(+0) |    4(+0) |    25(+0) |
| mbed-os/CMakeFiles |  48198(+0) |  456(+0) |  9686(+0) |
| source/CMakeFiles  |    958(+0) |   32(+0) |   444(+0) |
| Subtotals          | 105940(+0) | 2312(+0) | 10608(+0) |
Total Static RAM memory (data + bss): 12920(+0) bytes
Total Flash memory (text + data): 108252(+0) bytes

and the first time after deleting the folder:

-- Mbed: First CMake run detected, generating configs...
mbed_config.cmake has been generated and written to '/home/sam/git/hmc20_ce_test/build/develop/mbed_config.cmake'

[lefebvresam]

I guess that in MBEDTOOLS_CONFIGURE_COMMAND there must be something as a default location.

[JohnK1987]

maybe?

mbed-os/tools/cmake/mbed_generate_configuration.cmake

Lines 9 to 10 in f19273a

	# MBED_APP_JSON_PATH - Path to mbed_app.json. If relative, will be interpreted relative to CMAKE_SOURCE_DIR.
	# CUSTOM_TARGETS_JSON_PATH - Full path to custom_targets.json, may be set to empty/undefined if not using it. If relative, will be interpreted relative to CMAKE_SOURCE_DIR.

[lefebvresam]

Shoud dig into the code but for me it's not a blocking one. Just to understand 'the system'.

[JojoS62]

arm-mbed is usually only accepting targets that have the debug hardware included, that was a requirement for the 'mbed enabled' logo.
Blue/Blackpill boards don't have this onboard link and so they are harder and to test and to support. But an OS should not run only on Devboards, so it is a really important to have a good custom target supprt.
Bluepill can be a standard board in mbed-ce, the user has just to connect a debug probe and set the upload cfg. In this case, it should be possible also in application level so that not for every board a mbed-ce modification is neccessary.

[JohnK1987]

Yeah, I forgot this reason about onboard debugger, but how you wrote "usually". So according to Maxim's targets, the debugger can just be included in package and not onboard.
I agree with that. I believe that was the one of main points of Mbed's concept. Fast prototype with a dev board and easy switch to a custom board.

[lefebvresam]

@multiplemonomials To answer on your question of issue_393 I opened a test project for the bootloader with the same structure I currently use for the customized target. There you can see the only way I got it working with an almost empty c-file.

git clone [email protected]:saleconix/mcuboot.git

Later I will close this project and regenerate the keys.