Add RP2040 support

[multiplemonomials]

Summary of changes

This PR adds initial support for running Mbed on Raspberry Pi 2040 processors via the RASPBERRY_PI_PICO target. It's based on the PR Arduino created against mainline Mbed, but adapted to work with Mbed CE's CMake build system and with some extra bugfixes (BufferedSerial now works) and features (automated uploading and debugging).

Impact of changes

Mbed will now support the RPi Pico.

Migration actions required

Documentation

Wiki page is being worked on here.

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Pull request type

[] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[X] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[] Covered by existing mbed-os tests (Greentea or Unittest)
[X] Tests / results supplied as part of this PR

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Reviewers

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[multiplemonomials]

OK we're doing better with the latest round of fixes:

85% tests passed, 11 tests failed out of 71

Total Test time (real) = 1726.15 sec

The following tests FAILED:
          1 - mbed-drivers-ticker (Failed)
          2 - mbed-usb-device-basic (Failed)
          3 - mbed-usb-device-hid (Failed)
          4 - mbed-usb-device-msd (Failed)
          5 - mbed-usb-device-serial (Failed)
         10 - mbed-hal-flash-functional-tests (Failed)
         15 - mbed-hal-pinmap (Failed)
         17 - mbed-hal-reset-reason (Failed)
         19 - mbed-hal-rtc-reset (Failed)
         29 - mbed-hal-watchdog (Failed)
         31 - mbed-hal-watchdog-timing (Failed)
Errors while running CTest

I won't be working on USB tests as part of this PR, and mbed-hal-rtc-reset will always fail on this device because the RTC does not keep time through a reset. Also, mbed-hal-flash-functional-tests is failing because it seems the current flash api can't handle flash-to-flash program operations.

[multiplemonomials]

OK I think I have fixed nearly all the remaining tests or determined that they can't easily be fixed. Just have mbed-drivers-ticker left to investigate.

One other question in the meantime. @JohnK1987, what would happen if we needed to update the version of pico sdk included here? Did you make any changes to the SDK in the branch? Did you download the entire thing, or some subset of the files? We will probably want to make a plan for the day when it needs to be updated.

[JohnK1987]

One other question in the meantime. @JohnK1987, what would happen if we needed to update the version of pico sdk included here? Did you make any changes to the SDK in the branch? Did you download the entire thing, or some subset of the files? We will probably want to make a plan for the day when it needs to be updated.

I am not sure, but as a muster I used the data from PR mentioned in main post above and ArduinoCore-Mbed, but the SKD was downloaded from original repo and then was applied only change of name rtc_init, because of colision with Mbed's rtc_init.

• mbed-os/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_rtc/include/hardware/rtc.h

  Line 37 in 42e0780

  void _rtc_init(void);

• mbed-os/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_rtc/rtc.c

  Line 22 in 42e0780

  void _rtc_init(void) {

BR, Jan

[JohnK1987]

Ok, I was wrong. The steps what I descpripted previously are true but it was not in my repo, it was future plan. The version of SDK seems to be 1.3.0 but latest is 1.5.1.
Also only src folder is used.

[multiplemonomials]

All right, I fixed the us ticker test! @JohnK1987 this should be good to merge now! I will look into updating the SDK in a subsequent PR.

[JohnK1987]

Well done!