diff --git a/Makefile b/Makefile
index a7bcb900..bc15ed9a 100644
--- a/Makefile
+++ b/Makefile
@@ -99,21 +99,71 @@ BIN = _bin/$(BOARD)
 # Board specific
 -include src/boards/$(BOARD)/board.mk
 
-# MCU_SUB_VARIANT can be nrf52 (nrf52832), nrf52833, nrf52840
-ifeq ($(MCU_SUB_VARIANT),nrf52)
-  SD_NAME = s132
-  DFU_DEV_REV = 0xADAF
-  CFLAGS += -DNRF52 -DNRF52832_XXAA -DS132
-else ifeq ($(MCU_SUB_VARIANT),nrf52833)
-  SD_NAME = s140
+#---------------------------------
+# Select the softdevice to build for
+#---------------------------------
+ifeq ($(SD),s140)
+  CFLAGS += -DS140 -DBLE
   DFU_DEV_REV = 52840
-  CFLAGS += -DNRF52833_XXAA -DS140
-else ifeq ($(MCU_SUB_VARIANT),nrf52840)
-  SD_NAME = s140
+  ifeq ($(MCU_SUB_VARIANT),nrf52833)
+    CFLAGS += -DNRF52833_XXAA
+  else ifeq ($(MCU_SUB_VARIANT),nrf52840)
+    CFLAGS += -DNRF52840_XXAA
+  else
+    $(error Sub Variant $(MCU_SUB_VARIANT) is invalid for softdevice $(SD))
+  endif
+else ifeq ($(SD),s340)
+  $(info Build specified supporting both ANT and BLE)
+  $(warning Ensure you download a dualstack softdevice from thisisant.com)
+  $(warning Make sure to compile against the dualstack softdevice headers)
+  CFLAGS += -DS340 -DBOTH
   DFU_DEV_REV = 52840
-  CFLAGS += -DNRF52840_XXAA -DS140
+  ifeq ($(MCU_SUB_VARIANT),nrf52833)
+    CFLAGS += -DNRF52833_XXAA
+  else ifeq ($(MCU_SUB_VARIANT),nrf52840)
+    CFLAGS += -DNRF52840_XXAA
+  else
+    $(error Sub Variant $(MCU_SUB_VARIANT) is invalid for softdevice $(SD))
+  endif
+else ifeq ($(SD),s132)
+  CFLAGS += -DS132 -DBLE
+  DFU_DEV_REV = 0xADAF
+  ifeq ($(MCU_SUB_VARIANT),nrf52)
+    CFLAGS += -DNRF52832_XXAA
+  else
+    $(error Sub Variant $(MCU_SUB_VARIANT) is invalid for softdevice $(SD))
+  endif
+else ifeq ($SD, s332)
+  $(info Build specified supporting both ANT and BLE)
+  $(warning Ensure you download a dualstack softdevice from thisisant.com)
+  $(warning Make sure to compile against the dualstack softdevice headers)
+  CFLAGS += -DS332 -DBOTH
+  DFU_DEV_REV = 0xADAF
+  ifeq ($(MCU_SUB_VARIANT),nrf52)
+    CFLAGS += -DNRF52832_XXAA
+  else
+    $(error Sub Variant $(MCU_SUB_VARIANT) is invalid for softdevice $(SD))
+  endif
+else ifeq ($SD,)
+  # SD not specified, default to BLE SDs
+  ifeq ($(MCU_SUB_VARIANT),nrf52)
+    SD = s132
+    DFU_DEV_REV = 0xADAF
+    CFLAGS += -DNRF52 -DNRF52832_XXAA -DS132 -DBLE
+  else ifeq ($(MCU_SUB_VARIANT),nrf52833)
+    SD = s140
+    DFU_DEV_REV = 52840
+    CFLAGS += -DNRF52833_XXAA -DS140 -DBLE
+  else ifeq ($(MCU_SUB_VARIANT),nrf52840)
+    SD = s140
+    DFU_DEV_REV = 52840
+    CFLAGS += -DNRF52840_XXAA -DS140 -DBLE
+  else
+    $(error Sub Variant $(MCU_SUB_VARIANT) is unknown)
+  endif
 else
-  $(error Sub Variant $(MCU_SUB_VARIANT) is unknown)
+  # Invalid SD was specified
+  $(error softdevice $(SD) is unknown)
 endif
 
 #------------------------------------------------------------------------------
@@ -289,7 +339,7 @@ CFLAGS += -DSOFTDEVICE_PRESENT
 CFLAGS += -DDFU_APP_DATA_RESERVED=7*4096
 
 CFLAGS += -DUF2_VERSION='"$(GIT_VERSION) $(GIT_SUBMODULE_VERSIONS)"'
-CFLAGS += -DBLEDIS_FW_VERSION='"$(GIT_VERSION) $(SD_NAME) $(SD_VERSION)"'
+CFLAGS += -DBLEDIS_FW_VERSION='"$(GIT_VERSION) $(SD) $(SD_VERSION)"'
 
 _VER = $(subst ., ,$(word 1, $(subst -, ,$(GIT_VERSION))))
 CFLAGS += -DMK_BOOTLOADER_VERSION='($(word 1,$(_VER)) << 16) + ($(word 2,$(_VER)) << 8) + $(word 3,$(_VER))'
diff --git a/README.md b/README.md
index 83e75637..7c3fea94 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,7 @@ For other boards, please check the board definition for details.
 
 ### Making your own UF2
 
-To create your own UF2 DFU update image, simply use the [Python conversion script](https://github.com/Microsoft/uf2/blob/master/utils/uf2conv.py) on a .bin file or .hex file, specifying the family as **0xADA52840**. If using a .bin file with the conversion script you must specify application address with the -b switch, this address depend on the SoftDevice size/version e.g S140 v6 is 0x26000 
+To create your own UF2 DFU update image, simply use the [Python conversion script](https://github.com/Microsoft/uf2/blob/master/utils/uf2conv.py) on a .bin file or .hex file, specifying the family as **0xADA52840**. If using a .bin file with the conversion script you must specify application address with the -b switch, this address depend on the SoftDevice size/version e.g S140 v6 is 0x26000
 
 To create a UF2 image from a .bin file:
 ```
@@ -111,25 +111,25 @@ Prerequisites
 To build:
 
 ```
-make BOARD=feather_nrf52840_express all
+make BOARD=feather_nrf52840_express SD=s140 all
 ```
 
 To flash the bootloader with JLink:
 
 ```
-make BOARD=feather_nrf52840_express flash
+make BOARD=feather_nrf52840_express SD=s140 flash
 ```
 
 To upgrade the bootloader using DFU Serial via port /dev/ttyACM0
 
 ```
-make BOARD=feather_nrf52840_express SERIAL=/dev/ttyACM0 dfu-flash
+make BOARD=feather_nrf52840_express SERIAL=/dev/ttyACM0 SD=s140 dfu-flash
 ```
 
 To flash SoftDevice (and chip erase):
 
 ```
-make BOARD=feather_nrf52840_express sd
+make BOARD=feather_nrf52840_express SD=s140 sd
 ```
 
 For the list of supported boards, run `make` without `BOARD=` :
@@ -141,6 +141,26 @@ Supported boards are: feather_nrf52840_express feather_nrf52840_express pca10056
 Makefile:90: *** BOARD not defined.  Stop
 ```
 
+The supported protocols are currently BLE and BOTH (ANT + BLE).
+
+### Building with an ANT softdevice
+
+Currently, the bootloader can be built against the dualstack softdevice headers for
+use of both ANT and BLE simultaneously. To do this:
+
+1. Download either s332 or s340 from thisisant.com. Note that this softdevice is
+   freely available for evaluation use only. Garmin Canada must be contacted to obtain
+   ANT licenses for commercial use.
+2. Place the contents of the softdevice package in the appropriate lib/softdevice folder.
+3. Rename the API folder to <SD name>_nrf52_6.1.1_API.
+4. Rename the softdevice hex to <SD name>_nrf52_6.1.1_softdevice.hex.
+5. When building make sure to set SD=s340 or SD=s332
+
+All bootloader features available in the single-stack BLE softdevice are also available in the
+dualstack softdevice, including OTA-DFU updates using BLE.
+
+Note that single stack ANT softdevices are not currently supported (s2xx series softdevices).
+
 ### Common makefile problems
 
 #### 1. `arm-none-eabi-gcc`: No such file or directory
@@ -148,7 +168,7 @@ Makefile:90: *** BOARD not defined.  Stop
 If you get the following error ...
 
 ```
-$ make BOARD=feather_nrf52840_express all 
+$ make BOARD=feather_nrf52840_express all
 Compiling file: main.c
 /bin/sh: /usr/bin/arm-none-eabi-gcc: No such file or directory
 make: *** [_build/main.o] Error 127
diff --git a/lib/softdevice/s332_nrf52_6.1.1/README.txt b/lib/softdevice/s332_nrf52_6.1.1/README.txt
new file mode 100644
index 00000000..bb4bec19
--- /dev/null
+++ b/lib/softdevice/s332_nrf52_6.1.1/README.txt
@@ -0,0 +1 @@
+Obtain the 6.1.1 s332 softdevice from thisisant.com and place the API folder and softdevice hex here.
\ No newline at end of file
diff --git a/lib/softdevice/s340_nrf52_6.1.1/README.txt b/lib/softdevice/s340_nrf52_6.1.1/README.txt
new file mode 100644
index 00000000..fb0f5a0a
--- /dev/null
+++ b/lib/softdevice/s340_nrf52_6.1.1/README.txt
@@ -0,0 +1 @@
+Obtain the 6.1.1 s340 softdevice from thisisant.com and place the API folder and softdevice hex here.
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
index cf05c1af..a1ee2407 100644
--- a/src/main.c
+++ b/src/main.c
@@ -155,7 +155,7 @@ void softdev_mbr_init(void)
 //--------------------------------------------------------------------+
 int main(void)
 {
-  PRINTF("Bootlaoder Start\r\n");
+  PRINTF("Bootloader Start\r\n");
 
   // Populate Boot Address and MBR Param into MBR if not already
   // MBR_BOOTLOADER_ADDR/MBR_PARAM_PAGE_ADDR are used if available, else UICR registers are used
@@ -328,7 +328,13 @@ static uint32_t softdev_init(bool init_softdevice)
       .accuracy     = NRF_CLOCK_LF_ACCURACY_250_PPM
   };
 
+#ifdef BLE
   APP_ERROR_CHECK( sd_softdevice_enable(&clock_cfg, app_error_fault_handler) );
+#elif defined(BOTH)
+  APP_ERROR_CHECK( sd_softdevice_enable(&clock_cfg, app_error_fault_handler, ANT_LICENSE_KEY ) );
+#else
+  #error "No valid protocol was selected"
+#endif // BLE
   sd_nvic_EnableIRQ(SD_EVT_IRQn);
 
   /*------------- Configure BLE params  -------------*/