Update pico-sdk submodule commit point

[caternuson]

The current pico-sdk sudmodule commit point is prior to a fixed added to help with startup timing for the crystal. See here for more information:
raspberrypi/pico-sdk#457

Once updated, this hack should be able to be removed from the CI worflow:

u2if/.github/workflows/build_uf2.yml

Lines 16 to 21 in 945423f

	#-- HACK-----------------------------------------------------------
	# needed for older pico-sdk, see here for more info:
	# https://github.com/raspberrypi/pico-sdk/pull/457
	- name: Patch pico-sdk for crystal startup
	run: sed -i 's/xosc_hw->startup = startup_delay;/xosc_hw->startup = startup_delay * 64;/' firmware/pico-sdk/src/rp2_common/hardware_xosc/xosc.c
	#-- HACK-----------------------------------------------------------

[caternuson]

This may require more work than just updating the pico-sdk submodule. The pico-sdk in turn has tinyusb as a submodule. There have been some breaking changes to tinyusb that will require additional code changes in the u2if source code.

[freemansoft]

How do you test a board to know if this timer hack is still required? Upgrading pico-sdk went without a hitch in the PR that we closed. I only tested on two devices.

[caternuson]

A board running firmware built without the hack will not enumerate when plugged in or reset. Easiest way to know if this hack is needed is to just look at the file the sed command is altering.

Can also follow the linked pull request for more info and to see what the changes were that fixed it.

[freemansoft]

So if I built my images using the build-all.sh which does not have the hack and with pic-sdk 2.1.0 and my board enumerates then the hack won't be needed any more?

Thanks for replying by the way. I know this isn't the highest priority item.

[caternuson]

I think you still need to deal with it. But you don't need to modify source code. Can define a value for PICO_XOSC_STARTUP_DELAY_MULTIPLIER on command line, and set it to 64.