diff --git a/Makefile b/Makefile
index cd08e55..8e1abe5 100644
--- a/Makefile
+++ b/Makefile
@@ -15,7 +15,10 @@ TUSB_PATH    = lib/tinyusb/src
 NRFX_PATH    = lib/nrfx
 SD_PATH      = lib/softdevice/$(SD_FILENAME)
 
-SD_VERSION   = 7.2.0
+ifndef SD_VERSION
+   SD_VERSION   = 6.1.1
+endif
+
 SD_FILENAME  = $(SD_NAME)_nrf52_$(SD_VERSION)
 SD_HEX       = $(SD_PATH)/$(SD_FILENAME)_softdevice.hex
 
diff --git a/src/boards/nrf52833/board.mk b/src/boards/nrf52833/board.mk
index a979f7e..d76b2b7 100644
--- a/src/boards/nrf52833/board.mk
+++ b/src/boards/nrf52833/board.mk
@@ -1 +1,2 @@
-MCU_SUB_VARIANT = nrf52833
\ No newline at end of file
+MCU_SUB_VARIANT = nrf52833
+SD_VERSION=7.2.0
\ No newline at end of file
diff --git a/src/boards/pca10100/board.mk b/src/boards/pca10100/board.mk
index d60ac48..d76b2b7 100644
--- a/src/boards/pca10100/board.mk
+++ b/src/boards/pca10100/board.mk
@@ -1 +1,2 @@
 MCU_SUB_VARIANT = nrf52833
+SD_VERSION=7.2.0
\ No newline at end of file