[jgastonraoul]

Summary

Fixes an incorrect TARGET_NAME / TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS define in the SEEED_XIAO_NRF52840_SENSE_PLUS variant. The variant's defines.txt still carries the target name of the plain SEEED_XIAO_NRF52840_PLUS variant (no "Sense"), which appears to be a leftover from copying that variant's generated files when the Sense Plus variant was added.

Problem

Third-party libraries commonly guard board-specific behavior behind the TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS define — for example, Seeed_Arduino_LSM6DS3 uses it to redirect the onboard IMU to the internal Wire1 bus and to enable PIN_LSM6DS3TR_C_POWER, both required for the onboard LSM6DS3TR-C to respond on this board.

Because the variant's defines.txt defines TARGET_SEEED_XIAO_NRF52840_PLUS instead, that #ifdef never triggers, and the onboard IMU is silently undetectable on this variant when using this core — with no compile-time warning, since the code compiles fine either way.

Root cause

variants/SEEED_XIAO_NRF52840_SENSE_PLUS/defines.txt
-DTARGET_NAME=SEEED_XIAO_NRF52840_PLUS <- should be SEEED_XIAO_NRF52840_SENSE_PLUS
-DTARGET_SEEED_XIAO_NRF52840_PLUS <- should be SEEED_XIAO_NRF52840_SENSE_PLUS

Both defines match the SEEED_XIAO_NRF52840_PLUS (no Sense) variant's defines.txt exactly, which strongly suggests these files were copied from that variant when SEEED_XIAO_NRF52840_SENSE_PLUS was created, without regenerating the target-specific defines.

Scope of the fix

This PR only touches defines.txt. I checked whether includes.txt (which references TARGET_SEEED_XIAO_NRF52840_PLUS in an mbed-os include path) needed the same treatment, but confirmed there is no dedicated cores/arduino/mbed/targets/.../TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS directory in this core — only TARGET_SEEED_XIAO_NRF52840_PLUS and TARGET_SEEED_XIAO_NRF52840_SENSE exist. The Sense Plus variant genuinely borrows the Plus variant's mbed-os target tree (which makes sense, since the underlying SoC/SDK support is identical — only the PCB differs, adding the onboard IMU/mic). So includes.txt is correct as-is and should not be changed; the preprocessor-level TARGET_NAME/TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS defines are what's actually broken and consumed by userland code.

Testing

Verified on physical hardware (Seeed XIAO nRF52840 Sense Plus, this core installed via Boards Manager, v2.9.3): before this fix, Seeed_Arduino_LSM6DS3's imu.begin() fails to detect the onboard LSM6DS3TR-C. After applying this fix, TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS is correctly defined, the library's existing #if defined(TARGET_SEEED_XIAO_NRF52840_SENSE_PLUS) branch triggers as intended, and the onboard IMU is detected and reads correctly with no changes needed on the library or sketch side.