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Optional softdevice in nordic port - #11251
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A board sets `SD =` (empty) in its mpconfigboard.mk to build without a SoftDevice, reclaiming the MBR + SoftDevice flash and the 56kB of low RAM they reserve. Boards that do not opt out are unaffected. - Makefile: build the bluetooth sources only when SD is set, and link firmware.hex rather than firmware.combined.hex when there is no SoftDevice hex to merge in. Guard the bluetooth_common.mk include with VALID_BOARD so non-board rules such as fetch-port-submodules do not evaluate SoftDevice paths built from an unset MCU_VARIANT. - mpconfigport.mk: force _bleio and the BLE file/serial services off when SD is empty. - mpconfigport.h: without a SoftDevice its headers are not on the include path, so define MBR_SIZE and SD_FLASH_SIZE to 0 locally, and zero both CIRCUITPY_BLE_CONFIG_SIZE (nothing to bond) and SOFTDEVICE_RAM_SIZE. - startup_nrf52840.c: with a SoftDevice the MBR at 0x0 owns the vector table and has already pointed VTOR at ours. Without one, set it. - microcontroller/__init__.c: replace the sd_nvic critical-region calls with PRIMASK save/mask/restore, and write GPREGRET directly. - port.c, PinAlarm.c, neopixel_write, nvm.h: guard SoftDevice headers and calls. port_idle_until_interrupt()'s existing non-SoftDevice path becomes the fallthrough. Built and verified on feather_nrf52840_express (SoftDevice, byte-identical apart from port_idle_until_interrupt), microbit_v2 (nRF52833), and a throwaway SD-less board.
tannewt
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Aug 26, 2026
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Instead of introducing a SD make variable, let's use CIRCUITPY_BLEIO_NATIVE throughout. The mpconfigport does this as ?= so the board should be able to override it.
(I'm sure the actual code changes are fine.)
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Changed in the latest commit to use I retested it successfully on CPB. Same flashing warning from the original comment stands. It's possible to flash to a No-SD build with UF2, but SWD is required to return back to a standard build with SD. |
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This change adds a build flag to disable SoftDevice, set
SD=in mpconfigboard.mk file to disable.My testing was performed on a CircuitPlayground bluefruit and the LED Glasses driver device.
Flashing the UF2 file from a no SD build will wipe the SD from flash. Afterwards, flashing back to a normal with a SD-enabled UF2 file does not work. It flashes but the resulting firmware can't boot successfully. Getting back to a functional SD-enabled firmware requires using SWD to erase, and flash the bootloader+sd hex, then a standard release UF2 can be used to load CircuitPython and bring the device back to normal.