Add STM32U073Cx & STM32U083Cx boards

[ndoo]

Summary

Adds board definitions for the STM32U0 series (Cortex-M0+, 56 MHz, 40 KB RAM) and
the required OpenOCD fix to flash them.

New boards

STM32U073 - 12 generic variants (all variants supported by upstream Arduino STM32 core)

Package	64K (x8)	128K (xB)	256K (xC)
C-T	genericSTM32U073C8T	genericSTM32U073CBT	genericSTM32U073CCT
C-U	genericSTM32U073C8U	genericSTM32U073CBU	genericSTM32U073CCU
R-I	genericSTM32U073R8I	genericSTM32U073RBI	genericSTM32U073RCI
R-T	genericSTM32U073R8T	genericSTM32U073RBT	genericSTM32U073RCT

STM32U083 (all variants supported by upstream Arduino STM32 core, including Nucleo U083RC)

Board	Notes
genericSTM32U083CCT	C-package, LQFP48
genericSTM32U083CCU	C-package, QFN48
genericSTM32U083RCI	R-package, BGA64
genericSTM32U083RCT	R-package, LQFP64
nucleo_u083rc	ST eval board, onboard ST-Link

OpenOCD version bump and hla_swd deprecation

xpack OpenOCD 0.12.0-5 (2025-02-05) deprecated the HLA layer for ST-Link and
converted all interface scripts from transport select hla_swd to swd. Using
hla_swd with xpack ≥ 0.12.0-5 causes OpenOCD to error out. This PR changes
platform.py to always emit transport select swd for all adapters, and bumps
tool-openocd to ~3.1200.5 — also the first release that ships stm32u0x.cfg
(required to target STM32U0).

Note: the PlatformIO registry currently only has tool-openocd @ 3.1200.0.
Users must install xpack OpenOCD ≥ 0.12.0-5 manually until the registry is updated.
Attached is a script to locally update OpenOCD to 0.12.0-7 on MacOS:
install-openocd.sh

Blink test

Test sketch in tests/ updated to include all new boards, this was used to test actual hardware (refer to list below).

Tested on

• All 17 new environments build successfully (Arduino blink, local platform)
• genericSTM32U073CBT flashed and verified on actual hardware
• nucleo_u083rc flashed and verified on actual hardware

Closes: #798

[ndoo]

This also requires tool-openocd to be updated to at least xpack openocd v0.12.0-5 (though newer/latest would be nice), the current version in PIO is very very old cc @valeros @ilg-ul

[nschurando]

@valeros I second this PR.

[ndoo]

Since quite a length of time has passed without any review/activity from upstream, I have taken the liberty to:

1. Rebase on develop HEAD since 2 major versions have since been released
2. Flesh out the PR with full support for the entire range of STM32U073 and STM32U083 that is supported in STM32duino, including the Nucleo-U083RC
3. Properly set the OpenOCD dependency
   • The upstream version doesn't exist yet
   • I attached a script to the PR (only tested on MacOS) that overrides the local PlatformIO OpenOCD package to a newer version so that this PR works for flashing over SWD (or any other protocols that will use OpenOCD)
4. Add the new boards to the test sketch

---

Further details:

Commit f7fa973 → Add STM32U0 series board support:

• 16 generic boards - all U073/U083 generic boards in STM32duino core + nucleo_u083rc

Commit 9430683, Fix stlink transport and bump minimum OpenOCD to 3.1200.5:

• platform.py: transport select hla_swd (stlink) / swd (others) → always swd (hla_swd is deprecated as of OpenOCD 3.12-5)
• platform.json: tool-openocd ~3.1200.0 → ~3.1200.5.

These are coupled: 0.12.0-5 is both the first release with stm32u0x.cfg (needed for
STM32U0 targets) and the release that drops the HLA layer for ST-Link.

Commit b3a8668 → Add Arduino blink tests for STM32U073/U083 boards:

• 17 environments added to tests/arduino-blink-different-cores/platformio.ini.
• All 17 build clean
• genericSTM32U073CBT flashed and verified on actual hardware
• nucleo_u083rc flashed and verified on actual hardware

[ndoo]

My bad, looks like tool-openocd 3.1200.7 has landed so this PR should not need an out-of-tree OpenOCD (but the hla_swd fix is still needed, once the pinned version in platform-ststm32 is moved to 3.1200.7).

[ndoo]

My bad, looks like tool-openocd 3.1200.7 has landed so this PR should not need an out-of-tree OpenOCD (but the hla_swd fix is still needed, once the pinned version in platform-ststm32 is moved to 3.1200.7).

Oh, just checked. Not supported. But at least a custom upload_command and stm32cubeprogrammer works well with my PR changeset.