nRF52840 – flashing the s340 v6.1.1 SoftDevice

This post is a work in progress (WIP). The result of this experiment is a success. I have flashed my SparkFun nRF52840 mini, and I’m able to run the bicycle combined speed & cadence sensor example.

Before we begin,  a big hats off to Charles, who brought support for the SparkFun board I have to the Adafruit nRF52 bootloader. Cheers Charles! I owe you a beer :) – GitHub profile, blog

Important software versions:

nRF SDK: nRF5_SDK_15.3.0_59ac345
ARM GCC: 8.2.1
s340: s340_nrf52_6.1.1
board: SparkFun Pro nRF52840 mini

Rough outline:

1. Checkout ‘s PR

2. Copy over src/linker/s140_v6.ld to src/linker/s340_v6.ld – there are zero differences between these two files

3. Patch your main.c from the checked out source to initialise the soft device with the ANT_LICENSE_KEY

diff –git a/src/main.c b/src/main.c
index 8ac1dba..2e43f49 100644
— a/src/main.c
+++ b/src/main.c
@@ -301,7 +301,7 @@ static uint32_t softdev_init(bool init_softdevice)
APP_ERROR_CHECK( sd_softdevice_enable(&clock_cfg, app_error_fault_handler) );
+ APP_ERROR_CHECK( sd_softdevice_enable(&clock_cfg, app_error_fault_handler, ANT_LICENSE_KEY) );
/*————- Configure BLE params ————-*/

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4. Patch the Makefile to use the s340 soft device files

diff –git a/Makefile b/Makefile
index 6dbaf98..4acd319 100644
— a/Makefile
+++ b/Makefile
@@ -104,7 +104,7 @@ ifneq ($(IS_52832),)
SD_NAME = s132
SD_NAME = s140
+SD_NAME = s340
DFU_DEV_REV = 52840
@@ -275,7 +275,7 @@ CFLAGS += -DNRF52832_XXAA
CFLAGS += -DS132
CFLAGS += -DS140
+CFLAGS += -DS340
@@ -314,7 +314,7 @@ ASMFLAGS += -DNRF52

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5. Place the contents of the s340 archive (sign up for the evaluation licence from, wait for 1 business day, and then download the s340 soft device)

$ tree lib/softdevice/s340_nrf52_6.1.1/
├── s340_nrf52_6.1.1_API
│   └── include (all header files must be under here)
└── s340_nrf52_6.1.1_softdevice.hex

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6. Flash your nRF52840 device (double reset to enter the DFU mode)

$ make BOARD=sparkfun_pro_nrf52840_mini SERIAL=/dev/tty.usbmodem14301 dfu-flash

7. Verify

When you enter DFU mode after the above command completes, the contents of INFO_UF2.TXT must look something like the contents here:

UF2 Bootloader 0.2.10-4-g79fe6cc-dirty lib/nrfx (v1.1.0-1-g096e770) lib/tinyusb (legacy-755-g55874813) s340 6.1.1
Model: SparkFun Pro nRF52840 Mini
Board-ID: SparkFun-Pro-nRF52840-Mini
Bootloader: s340 6.1.1
Date: Jul 12 2019

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Very important – update your app’s linker script:

Since your board now runs the s340 soft device, update the FLASH and RAM values in your app’s linker script:

# diff diff ~/developer/em/nRF5_SDK_15.3.0_59ac345/examples/ant/ant_plus/ant_bsc/bsc_tx/pca10040/s212/armgcc/ant_bsc_tx_gcc_nrf52.ld ~/developer/em/bia/src/ant_bsc_tx_gcc_nrf52.ld
< FLASH (rx) : ORIGIN = 0x12000, LENGTH = 0x6e000
< RAM (rwx) : ORIGIN = 0x20000b80, LENGTH = 0xf480
> FLASH (rx) : ORIGIN = 0x00031000, LENGTH = 0x000F4000-0x00031000
> RAM (rwx) : ORIGIN = 0x20002000, LENGTH = 0xf480

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The new values are not black magic. They’re documented here:


  • RAM and FLASH addresses:
  • MBR and boot loader info from Nordic:
  • Reading boot loader settings:
  • Usage of MBR params:
  • Segger J-Link Mini:


Random notes below, don’t follow any of it, or execute any commands from here on out. You’ve been warned.

FLASH and RAM for s340 6.1.1:

S340- 6.1.1

Min RAM start: 0x20002000

Flash start: 0x31000


Generate boot loader settings:

(nrfutil) h2:nrfutil jude$ nrfutil settings generate –family NRF52840 –softdevice ../nRF5_SDK_15.3.0_59ac345/components/softdevice/s112/hex/s112_nrf52_6.1.1_softdevice.hex –bootloader-version 1 –bl-settings-version 1 a.hex


$ git status

h2:Adafruit_nRF52_Bootloader jude$ git status
On branch master
Your branch is up to date with 'origin/master'.
Changes not staged for commit:
(use "git add <file>…" to update what will be committed)
(use "git checkout — <file>…" to discard changes in working directory)
modified: Makefile
modified: src/main.c
Untracked files:
(use "git add <file>…" to include in what will be committed)
no changes added to commit (use "git add" and/or "git commit -a")
h2:Adafruit_nRF52_Bootloader jude$

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