[Board]: XIAO nRF54L15: BLE/GPS bring-up fixes and XIAO nRF54L15 + Wio-SX1262 variant (tracking)

[hackengineer]

SOC

Other

Lora IC

Wio-SX1262

Product Link

https://www.seeedstudio.com/XIAO-nRF54L15-p-6493.html

Description

Tracking issue for a series of nRF54L15 port fixes and a new variant,
developed and hardware-verified on a Seeed XIAO nRF54L15 Sense +
Wio-SX1262 (+ L76K GNSS). Opening this per the PR guidelines to give the
individual PRs shared context.

Problem: on current develop, the nRF54L15 port advertises but cannot
complete the phone-API bootstrap — the app stalls during/after service
discovery, secure pairing dies right after the PIN is displayed, and
config-required reboots silently don't happen.

Root causes found (each with its own fix):

Cause	Effect	Fix
RC sleep clock (K32SRC_RC in prj.conf) wedges the SW link layer	ATT TX stalls after exactly BT_BUF_ACL_TX_COUNT unacked PDUs; lost disconnects; Controller unresponsive	#11471 (verified by A/B/A on hardware; also removes the PHY/DLE workarounds that were masking it)
resumeAdvertising() called from SMP callback context / mid-connection via PowerFSM	secure pairing stalls after PIN display	#11471
Phone's eager fromRadio read races the deferred ToRadio processing	iOS app waits for a notify that never comes, disconnects ~30 s after want_config	#11471
Power::reboot() has no nRF54L15 branch	admin/config reboots are silent no-ops	#11471
MyNodeInfo.pio_env unterminated with 40+ char env names	nanopb refuses MyInfo, config stream yields 0 bytes	#11468 (merged — thanks @caveman99)
GPS probe indexes rareSerialSpeeds[] out of bounds after a failed scan	garbage-baud probes on GPS re-enable	#11470

PR series:

• Fix unterminated MyNodeInfo.pio_env when APP_ENV is 40+ chars #11468 — pio_env termination (merged)
• Fix out-of-bounds baud table read when GPS is re-enabled after failed probe #11470 — GPS probe bounds fix (5 lines, CI green)
• nrf54l15: fix BLE phone-API bootstrap (sleep clock, adv restart, ToRadio race, reboot) #11471 — nRF54L15 BLE fixes (4 commits, CI green)
• Add Seeed XIAO nRF54L15 Sense + Wio-SX1262 variant with GPS and IMU support #11472 — XIAO nRF54L15 Sense + Wio-SX1262 variant with GPS (L76K)
  and IMU (LSM6DS3) support (draft, CI green — flips to ready once nrf54l15: fix BLE phone-API bootstrap (sleep clock, adv restart, ToRadio race, reboot) #11471
  lands)

Verified on hardware after the series: encrypted fixed-PIN pairing
(security level 4), bond persistence across reboots, full config streams to
the iOS app, LoRa mesh TX/RX/relay, GPS fixes (16+ sats, PDOP ~1), IMU
wake-on-motion.

Happy to rebase, split, or rework any of these however the maintainers
prefer, and I have the hardware on my desk for any requested testing.