boards/nrf52xxxdk: add openocd as programmer

For the moment openocd doesn't work when softdevice blob module is loaded

boards/common/nrf52xxxdk/Makefile.include

@@ -15,18 +15,29 @@ PORT_LINUX ?= /dev/ttyACM0
 PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.usbmodem*)))
 include $(RIOTMAKE)/tools/serial.inc.mk
 
-# setup JLink for flashing
-export JLINK_DEVICE := nrf52
-
 # The following configuration is dependencies specific
 # but they are resolved later
 # Hack to know now if 'nordic_softdevice_ble' is used
 include $(RIOTBOARD)/$(BOARD)/Makefile.dep
 
-# special options when using SoftDevice
-ifneq (,$(filter nordic_softdevice_ble,$(USEPKG)))
-  export JLINK_PRE_FLASH := erase\nloadfile $(BINDIR)/softdevice.hex
-  export FLASH_ADDR := 0x1f000
-  export LINKER_SCRIPT ?= $(RIOTCPU)/$(CPU)/ldscripts/$(CPU_MODEL)_sd.ld
+PROGRAMMER ?= jlink
+ifeq (jlink,$(PROGRAMMER))
+  # setup JLink for flashing
+  export JLINK_DEVICE := nrf52
+
+  # special options when using SoftDevice
+  ifneq (,$(filter nordic_softdevice_ble,$(USEPKG)))
+    export JLINK_PRE_FLASH := erase\nloadfile $(BINDIR)/softdevice.hex
+    export FLASH_ADDR := 0x1f000
+    export LINKER_SCRIPT ?= $(RIOTCPU)/$(CPU)/ldscripts/$(CPU_MODEL)_sd.ld
+  endif
+  include $(RIOTMAKE)/tools/jlink.inc.mk
+else ifeq (openocd,$(PROGRAMMER))
+  # openocd doesn't work (yet) with softdevice
+  ifneq (,$(filter nordic_softdevice_ble,$(USEPKG)))
+    $(error Cannot use OpenOCD with nordic_softdevice module)
+  endif
+  export DEBUG_ADAPTER ?= jlink
+  export OPENOCD_CONFIG := $(RIOTBOARD)/common/nrf52xxxdk/dist/openocd.cfg
+  include $(RIOTMAKE)/tools/openocd.inc.mk
 endif
-include $(RIOTMAKE)/tools/jlink.inc.mk

boards/common/nrf52xxxdk/dist/openocd.cfg

@@ -0,0 +1,3 @@
+transport select swd
+
+source [find target/nrf52.cfg]