Secure DFU OTA for nRF52832 solution modules: Guide to create hex/zip file for implementation – Part 1(Bootloader & Application)

Here are the guidelines for users to implement Secure DFU OTA(over-the-air) while using nRF52832 Solution modules. (Click on link for Raytac nRF52832 module series)

IC: nRF52832
DK: PCA10040 (for nRF52832)
SDK: 16.0.0
Softdevice: s132_nrf52_7.0.1_softdevice.hex
IDE: Keil C
PC: Win 10

Below are the guidelines to implement Secure DFU OTA by using Raytac’s nRF52832 modules, SDK16.0.0.
It consists of 2 parts:

Part 1: Bootloader & Application

Part 2: Combining and merging built files (Article link)

In this article, we will be focusing on Part 1: Bootloader & Application.

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Bootloader

Path: ..\nRF5_SDK_16.0.0_98a08e2\examples\dfu\secure_bootloader\pca10040_s132_ble\arm5_no_packs
Specifically for nRF52832, programmers need to embed ECC(Elliptic Curve Cryptography) into the bootloader.

Step 1. ’micro_ecc_lib_nrf52.lib’ library can be found in the path below, but we need to boot it up first.

Step 2. Unzip ’micro-ecc-master.zip’ to the below path(create a new “micro-ecc” file first).

Step 3. Run ’gcc-arm-none-eabi-7-2018-q2-update-win32.exe’.

Step 4. Make sure the Environment variables in Win10 are set as below. (Follow the steps 1 to 6)

Step 5. Open DOS → run the “make” command under armgcc path → generate’micro_ecc_lib_nrf52.lib’

Step 6. Add ’micro_ecc_lib_nrf52.lib’ into folder: nRF_micro-ecc

Step 7. An error may occur while building bootloader without a public key:
(Shown in red frames in below screenshot)

Step 8. How to generate the public key file in Bootloader?
A. Visit DOS at path: ..\Python27\Scripts
B. Then execute:

nrfutil keys generate private.pem
nrfutil keys display --key pk --format code private.pem --out_file public_key.c

Step 9. Copy the pk[64] code from (public_key.c) into (dfu_public_key.c)
(Shown in red frames in below screenshot)

※Note: Make sure to save the 3 generated files:
private.pem
public_key.c
dfu_public_key.c

Step 10. Generate the bootloader file: nrf52832_xxaa_s132.hex after re-compiling the code files.

Application

Path:
..\nRF5_SDK_16.0.0_98a08e2\examples\ble_peripheral\ble_app_uart\pca10040\s132\arm5_no_packs
Before building Application code , some amendments need to be made regarding DFU-related settings and code inside Application:

Step 1. Add code in definition in C/C++ :
BL_SETTINGS_ACCESS_ONLY NRF_DFU_SVCI_ENABLED NRF_DFU_TRANSPORT_BLE=1
(Total 3 steps definitions need to be set up)

Step 2. Add the 3 paths shown below in C/C++ to make DFU work.

Step 3. Add the .c files inside red frame in (Screenshots 1&2)
and add the 2 groups of (nRF_DFU & nRF_SVC)(Screenshot 4) under Project(Screenshot 3)

Step 4. Add code into main.c file in Application (..\examples\ble_peripheral\ble_app_uart\main.c)
(Please refer to: main.c file at: ..\examples\ble_peripheral\ ble_app_buttonless_dfu)

Step 5.
The code of file: sdk_config.h (..\examples\ble_peripheral\ble_app_uart\pca10040\s132\config\sdk_config.h)
inside Application needs to be modified.

Step 6. Adjust the IRAM1 value in Target after implementing DFU service:
Make sure the IRAM1 Value of *p_app_ram_start is modified 

from default: 0x20002AD8 0xD528 to 0x20002AE8 0xD518, as shown in the red frame in the bottom right corner.

In this case, the program should run/advertise successfully.

Step 7. Create a file of: nrf52832_xxaa.hex after building application code files.

Step 8. Create a bootloader setting file of nrf52832_bootloader_secure_settings.hex via DOS.
nrfutil settings generate –family NRF52 –application nrf52832_xxaa.hex –application-version 3 —
bootloader-version 2 –bl-settings-version 1 nrf52832_bootloader_secure_settings.hex –no-backup

※Stay tuned for Part 2: Combining and merging built files in the next article, scheduled release in next week(04-Sep-2024).

Technical guidelines provided by R&D Manager: Mr. MW Lee

Edited by Sales Manager: Ms. Mandy Chao

Raytac Corporation 勁達國際電子股份有限公司 
Raytac Corporation: A Bluetooth, Wi-Fi, and LoRa Module Maker based on
Nordic nRF54; nRF53: nRF52; nRF51; nRF7002
Semtech Specification: SX1262

Bluetooth Specification: BT5.4 ; BT5.3; BT5.2.
Wi-Fi Specification: Wi-Fi 6
LoRa Specification: LoRaWAN

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