STM32F746 Discovery board support

[mojzu]

Made an attempt at adding this myself but ended up making a lot of changes to default package directories which I'm unsure about. I can compile firmware successfully, but upload fails with scons error code 309 (guessing the tool-stlink binaries don't support the processor yet, but managed to get around this using ST's flashing tool and Em::block's STlinkGDB for debugging).

Changes:

• To support the Cortex-M7 I updated the toolchain in .platformio/packages/toolchain-gccarmnoneeabi
• Added new/changed files to .platformio/packages/framework-cmsis/cores/stm32 from stm32cubef7/Drivers/CMSIS/Include
• Added directory .platformio/packages/framework-cmsis/variants/stm32f7 with contents from stm32cubef7/Drivers/CMSIS/Device/ST/STM32F7xx
• Added linker script to .platformio/packages/ldscripts/stm32f746ng.ld from stm32cubef7/Projects/STM32746G-Discovery/Templates/SW4STM32/STM32746G_Discovery/STM32F746NGHx_FLASH.ld

And in the repository I added a board definition to platformio/boards/ststm32.json:

"disco_f746ng": {
    "build": {
        "core": "stm32",
        "extra_flags": "-DSTM32F746xx",
        "f_cpu": "216000000L",
        "ldscript": "stm32f746ng.ld",
        "cpu": "cortex-m7",
        "mcu": "stm32f746ngh6",
        "variant": "stm32f7"
    },
    "frameworks": ["cmsis"],
    "name": "ST STM32F7DISCOVERY",
    "platform": "ststm32",
    "upload": {
        "maximum_ram_size": 327680,
        "maximum_size": 1048576
    },
    "url": "http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1858/LN1902/PF260869",
    "vendor": "ST"
},

[ivankravets]

To support the Cortex-M7 I updated the toolchain in .platformio/packages/toolchain-gccarmnoneeabi

Which toolchain have you used?

[mojzu]

Version 4.9 update 3 from launchpad.

[ivankravets]

It looks that issue is fixed in PlatformIO 3.0. If it doesn't work, pelase open new issue here https://github.com/platformio/platform-ststm32/issues/new