nRF52832-buttonless-dfu-development-tutorial

This Windows tutorial is valid as of 2018-06-06, updates to tools and SDKs might have been made since then. Please review the information on our Infocenter.nordicsemi.com to see if any updates have been made.

This tutorial does not cover the installation and use of all the Nordic tools that are required to do follow this tutorial, the assumption is that you already know some of the basics for developing with a nRF SOC. Links are provided where I thought they would be needed, so please review this, and also use our DevZone portal to find answers to questions you might have.

Requirements

• SDK v15.0.0
• SEGGER Embedded Studio - see youtube playlist for information on setup
• armgcc compiler and make
• git
• nrfutil version 3.5.1, any later version should be fine to use, but might require some modifications to the scripts
• nrfjprog and mergehex version 9.7.1 or later
• 2x nRF52-DK (nRF52832 development kit, PCA10040)

To follow this tutorial, and if you prefer to not edit any of the provided .bat files, please do the following:

1. Download SDK v15.0.0 from here: http://developer.nordicsemi.com/nRF5_SDK/nRF5_SDK_v15.x.x/, and extract it into “C:\” drive, matching the path: “C:\nRF5_SDK_15.0.0_a53641a\license.txt”. I also suggest you make the entire folder into a .git repository as that makes it easier to see which changes that have been made later on.
2. Make sure nRF5x Command Line Tools, nRF5x CLT download is installed
3. Install nrfutil using Python pip.
4. Make sure nRF Connect is installed and that you know how to use it. The reason we require 2x nRF52-DKs, is that nRF Connect requires its own DK in order to run and perform the DFU updates. Please run through the nRF Connect Bluetooth low energy guide, and make sure you are able to establish a connection to a BLE device from the PC.
5. Make sure SEGGER Embedded Studio is installed and you know how to use it.

You can always edit the paths in the .bat files if you prefer to extract the SDK into some other folder on your machine.

Step 1 - Test Buttonless DFU Template Application

Go through the description here: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.0.0/ble_sdk_app_buttonless_dfu.html?cp=4_0_0_4_1_2_6, and make sure that you understand how this works. I will roughly list the steps below for the approach without bonds.

The steps you are going to do as part of testing Buttonless Secure DFU without bonds:

1. Flash the precompiled hex file using nrfjprog to the device DK (not the DK we are going to use with nRF Connect)

nrfjprog --program C:\nRF5_SDK_15.0.0_a53641a\examples\dfu\secure_dfu_test_images\ble\nrf52832\sd_s132_bootloader_buttonless_with_setting_page_dfu_secure_ble_debug_without_bonds.hex --chiperase

2. Power off the device DK
3. Connect the other DK that has not been programmed to the PC, open up nRF Connect BLE and use this other DK to start scanning for devices (choose serial port, program FW if not done already, start scan)
4. Power on the device DK that was programmed with the DFU test image, it should advertise as Nordic_Buttonless
5. Connect to the device DK from nRF Connect
6. Click on the DFU icon that should have appread in nRF Connect, and select the hrs_application_s132.zip from the same folder as the DFU test image FW. It should list package info which includes an application. Click Start DFU
7. Complete the update, then see that the HRS application starts up by scanning for it with nRF Connect. The name will now be Nordic_HRM, and if you connect, you can see the heart rate and battery updates as with the standard HRM example

This is what we are going to try and mimic when we are “developing” our own buttonless DFU FW. I say “developing” because we are not actually going to do any changes or development besides re-compiling the provided source files.

Step 2 - Create our own bootloader using our own private/public keys

Read through the instructions as provided for the BLE Secure DFU Bootloader on the infocenter: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.0.0/ble_sdk_app_dfu_bootloader.html?cp=4_0_0_4_1_3. A script is provided with this tutorial and this .bat can be used to create the private/public key pair using nrfutil, 01_generate_private_public_keys.bat. See http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.tools/dita/tools/nrfutil/nrfutil_intro.html?cp=5_5 for more information on nrfutil.

1. Create a private and public key using nrfutil by running script 01*.bat, this will generate private.pem and dfu_public_key.c
2. Copy the generated dfu_public_key.c into C:\nRF5_SDK_15.0.0_a53641a\examples\dfu folder, replacing the dfu_public_key file that is already in there.
3. Install micro-ecc. See infocenter BLE Secure DFU Bootloader, and Installing micro-ecc. When all the tools are installed (armgcc, make, git), you can run the C:\nRF5_SDK_15.0.0_a53641a\external\micro-ecc\build_all.bat script to install it
4. Compile C:\nRF5_SDK_15.0.0_a53641a\examples\dfu\secure_bootloader\pca10040_ble\ses\secure_bootloader_ble_s132_pca10040.emProject, which is the secure BLE bootloader for nRF52832
5. Copy the output bootloader .hex from \Output\Release\Exe\secure_bootloader_ble_s132_pca10040.hex into the same folder as the tutorial scripts, then rename it bootloader.hex
6. Program the s132_nrf52_6.0.0_softdevice.hex, as well as the bootloader.hex to the nRF52832 by running the script 02*.bat. If you have 2 DKs connected to the PC when you run this script, it will prompt you to select the Serial number of the DK you want to program. Select the Serial number of the device DK that is not used for nRF Connect
7. Power cycle the device DK, and it should start up and enter DFU mode and advertise as DfuTarg
8. Restart scanning from nRF Connect, and you should see this advertisement

At this point, you know that you can create your own bootloader with your own keys, and it will make the DK run and enter DFU mode.

Step 3 - Create our own FW.zip package which we can upload to the device over BLE

To create our own firmware package, we will be using nrfutil as we did in step 1. Please review the following page for more information: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.0.0/lib_bootloader_dfu_validation.html?cp=4_0_0_3_5_1_1_1#lib_dfu_image. We will be using a script to generate the .zip package 03_create_fw_zip_package.bat. This script assumes there is an app.hex, as well as the s132_nrf52_6.0.0_softdevice.hex present in the same folder as the script. There is also a 03b_create_fw_zip_package_noSD.bat that can be used to generate a FW.zip without a SD.

Generating firmware .zip package with application and SoftDevice

1. Make sure the s132 softdevice .hex file s132_nrf52_6.0.0_softdevice.hex is in the same folder as the script
2. Copy any application .hex file into the same folder as the script, and rename this file app.hex. I will be using the HRS application from C:\nRF5_SDK_15.0.0_a53641a\examples\ble_peripheral\ble_app_hrs\pca10040\s132\ses\Output\Release\Exe\ble_app_hrs_pca10040_s132.hex; you will have to compile this example to get the .hex file. Other examples can be used as well. Note: You cannot use the precompiled .hex files provided with the examples as these include the SoftDevice as well as the application FW
3. Run the 03_create_fw_zip_package.bat to generate a FW.zip package with SD + APP that can be uploaded to the DK over BLE DFU
   1. We will be using application-version 1 just because for demo purposes.
   2. We will be using application-version-string “1.0.0” for demo purposes.
   3. We will not be uploading a new bootloader to the device
   4. We will be requiring hw-version 52
   5. We will be requiring sd-req 0xA8 as this matches s132 v6.
   6. We will be using sd-id 0xA8 as we are uploading the same SD.
   7. We will be using the private key private.pem we generated earlier as input to --key-file
4. Once the FW.zip is generated, power cycle the device DK and make sure it starts advertising in bootloader mode as DfuTarg. If it does not, go back to the previous step and make sure that works
5. Connect to DfuTarg from nRF Connect
6. Click the DFU button, and browse to the FW.zip file we just created and select this one, click “Start DFU”. The SD will be uploaded first, then the application
7. The DFU process should finish without any errors, and once it’s done, the DK should now be advertising the application image you just uploaded, which in my case is the HRS example. You should verify this using nRF Connect – scan and find the ADV name Nordic_HRM

At this point, you should now have a working process for uploading new SD and APP images to the DK using BLE DFU and the private/public key pair you used earlier and which matches your bootloader.

Generating firmware .zip package with application only

If you would like to test another FW image besides the first one we just uploaded, and maybe without including the SoftDevice, do the following;

1. Copy another application .hex file into the folder and rename this app.hex, then run 03b_create_fw_zip_package_noSD.bat to create a new FW.zip package, this time only including an application
   1. I used my favorite application ble_app_uart, copied in the compiled .hex file from C:\nRF5_SDK_15.0.0_a53641a\examples\ble_peripheral\ble_app_uart\pca10040\s132\ses\Output\Release\Exe\ble_app_uart_pca10040_s132.hex, renamed it app.hex, ran the 03b_*.bat script to create the FW.zip
2. To get the DK back into DFU mode, hold button 4 while powering on the device DK
   1. It should enter DFU mode and DfuTarg should show up in nRF Connect when scanning
3. Connect to DfuTarg, then follow the same procedure as above to upload the new FW.zip package – you will now see that there is only app data in the .zip package, no SD included
4. The DFU process should finsh without any errors, and the DK is now advertising as Nordic_UART

Step 4 – Create a product release image including all components

When releasing a product, it doesn’t always make sense that you must upload the application through DFU the first time it is installed. You want to upload all components, SD + Bootloader + Settings + Application at the same time probably during production.

The bootloader is designed so that when the DK is powered on, it will amongst other things check if there is an application present in flash and if there is, it will boot into this application FW. If there is no application, it will boot into BOOTLOADER mode. Holding button 4 also forces the DK into bootloader mode regardless of there being an application present or not as we have seen in the previous steps.

Because of this behavior, when we flash a new application image we need to make sure the bootloader knows that there is an application present in memory – this is done using the nrfutil bootloader settings. These settings should be flashed together with the application to make sure the bootloader knows the application is there. These bootloader settings are the reason you cannot just load the application from SES while a bootloader is in place and expect it to boot up into the application FW. Since SES does not know nor upload any bootloader settings, the bootloader will assume the application is either not there, or that it is broken, and boot into bootloader mode.

The proper way to handle this would be:

1. Compile the application FW
2. Generate a settings.hex using this new application FW
3. While the SoftDevice and bootloader are already in place, upload both the application FW and the settings.hex at the same time
4. Once all this is done, power cycle the DK and it should show up running the new application FW

To test this, you can use script 04_bootloader_settings_merge_flash.bat. It will generate a settings.hex file based on the app.hex that is present in the folder. The script will then merge together the settings.hex and app.hex into one .hex file. Then the script will flash the merged hex file to the DK. You can verify this by changing out the app.hex, run script 04, power cycle the device DK, and make sure the new application is running by scanning for ADV’s in nRF Connect.

For example, if Nordic_UART is running right now, copy the HRS application into the folder and rename it app.hex, then run script 04, power cycle device DK and see that Nordic_HRM will now be advertising instead.

We now know how to upload new application FW while the bootloader is in place using the nRF5x command line programming tools. As noted earlier, you cannot go into the SES IDE, and click Download hex while using the secure BLE bootloader is in place as this will make the device boot into bootloader mode. Also, if your application assumes there is a bootloader in place and has functions calls that require it to be there, it will of course fail if the bootloader is not there.

Step 5 – Debugging Application FW with bootloader in place

To to debug an application FW while the bootloader is in place, there are different things that can be done. For one, you could disable any call to the bootloader in the application FW and then just run it without the bootloader in place. You can add debug log prints instead of having to actually debug the code. Another option is that you can upload the new application FW as described in step 4, and using SES as an example, just click Debug – Go. SES will check the flash content and see that it already matches the compiled .hex and not re-flash anything. You are now debugging the application FW with the bootloader installed.

I would suggest making a scrip that retrieves the compiled .hex file from the SES output folder, generates the settings.hex and flashes it automatically (see step 6). All you need to do then is just run the .bat script instead of clicking Download hex, and then you can go into Debug mode from the IDE. If you just uploaded the HRS example in step 04, open the SES project for HRS, then without changing any of the code (assuming you have just compiled the HRS and used that output .hex file in step 4), click Debug – Go; you should now be debugging the HRS application while the bootloader is in place.

Step 6 – Testing Buttonless DFU Example

Now that we know how this all works, we can test the buttonless DFU example in the same way.

1. Compile C:\nRF5_SDK_15.0.0_a53641a\examples\ble_peripheral\ble_app_buttonless_dfu\pca10040\s132\ses\ble_app_buttonless_dfu_pca10040_s132.emProject
2. If you did not install SDK v15.0.0 in the C drive, edit the 06_copy_buttonless_create_settings_merge_flash.bat script to match your PATHs
   1. This script will copy the compiled .hex file from the ble_app_buttonless output folder, rename it app.hex, then run 04.bat script which will generate the bootloader settings, merge the two together, then flash it to the DK
3. Run the 06*.bat script – this will flash the DK with the new buttonless app FW - make sure you select the device DK when SEGGER asks for the Serial number
4. Power cycle the DK, and with nRF Connect verify that it is running the buttonless app FW, advertising as Nordic_Buttonless
5. From the SES project, click Debug – Go, and you will now be debugging the buttonless FW application
6. Exit debug mode
7. Connect to Nordic_Buttonless from nRF Connect, then click the DFU button and select the FW.zip that we have generated earlier. The new FW.zip will be uploaded over BLE DFU, and the new application FW should boot when device DK reboots. If you have follow this guide step by step, the DK will now be advertising as Nordic_UART, and it does no longer have the buttonless DFU service. So getting back to DFU mode is done by holding down button 4 while power cycling the DK

We now have a buttonless DFU FW application working together with our bootloader and FW package generation. We can also debug the application if needed.