boards/weact-g030f6: add support for minimal break-out board

[benpicco]

Contribution description

This adds support for a cheap little board based on STM32G030F6.

It is pretty straightforward, except that there is no RTT. This uncovered a bug in stm32g0316-disco which I based this on where the board would not set TIMER_0_MAX_VALUE for the 16 bit timer, leading to way too early timeouts with ztimer_msec.

Since it's just a single line, I added the fix to this PR.

I also noticed that periph_rtc was not supported for this CPU family yet, so I added the required definitions.

I also noticed that I sometimes have trouble flashing the device with a DAP-Link Programmer with

Error: Error connecting DP: cannot read IDR

I then have to hold the reset button and release it once OpenOCD starts probing the CPU - I have NRST connected, so maybe my debugger is just not using it.

Testing procedure

RTC works with alarm:

2024-02-04 19:57:36,308 # > rtc gettime
2024-02-04 19:57:36,308 # 
2024-02-04 19:57:36,309 # 2024-02-04 19:57:33

2024-02-04 19:57:52,373 # > rtc setalarm 2024-02-04 19:58:00
2024-02-04 19:57:52,373 # 
2024-02-04 19:58:03,438 # > The alarm rang

I am a bit wondering if the alarm is working on STM32G4 as I would expect that it should select the same code path as STM32G0 (and STM32L5).
With the default the alarm would not get cleared and keep triggering.

Issues/PRs references

[riot-ci]

Murdock results

✔️ PASSED

e207848 boards/stm32g0316-disco: enable periph_rtc

Success	Failures	Total	Runtime
8627	0	8627	09m:56s

Artifacts

• Documentation preview