Firmware on custom board (Application + Bootloader)

[Tim Adu]

I've reached a critical point in the firmware development process where I need to start considering integrating a bootloader with the application code.

I have a custom board with an nrf52840 SoC. I have created a new bsp for the board and I'm able to execute code and run debugging on the board using Segger Embedded Studio. At some point, we'll have to integrate a bootloader in order to be able to create a release image.

Based on the requirements at my company, it has been decided to implement the application in two phases:

• Phase 1 will include the application and bootloader
• Phase 2 will include the application, bootloader and softdevice, once the BLE-related requirements have been locked.

I wish to implement phase 1 and as this is critical, I do not wish to get fragmented information.

My questions

1.  Are there any ready-made bootloaders I can use?
2. How do I go about combining the application and bootloader (without softdevice)
3. How do I fragment the flash memory so that I can have the application, bootloader, and eventually softdevice?
4. Are there any detailed tutorials explaining the integration processes?
5. Eventually we'll implement FOTA over Bluetooth. Anything I should be specially aware of here?

Any link to documentation/tutorials will be very much appreciated. I apologize in advance if the questions seem a bit broad. I'm a bit new to this process of integrating application code and bootloaders.

Thanks,

/Tim

[Edvin]

Hello Tim,

1: Yes, there is a bootloader in the SDK. I don't know what SDK version you use (which one is it?)

2: It is possible if you use the serial bootloader, but my impression is that the bootloader that uses BLE to transfer the application is the most used. If so, I would recommend going directly to phase 2.

3: The bootloader will take care of this. You can use a tool called nrfutil to create the DFU(/FOTA) images, and there you will set what the image contains (Bootloader, softdevice or application (or a combination).

4: Yes. Check out this tutorial, which will explain how to use the BLE bootloader. It is written for a fairly old SDK version (12.0.0), but you should be able to follow it using the latest SDK (SDK15.3.0) as well.

5: As mentioned, I suggest that you do this directly. The blogpost in the link above will take you through this.

I hope that clears up some of your questions. I suggest that you walk through the guide from the link (without your application, just use the examples from the SDK to get familiar with it), and then try to combine it with the example found in:

SDK\examples\ble_peripheral\ble_app_buttonless_dfu

And then move to including this in your application.

Let me know if you are stuck somewhere in the testing.

Best regards,

Edvin

[Tim Adu]

Thanks Edvin,

• I use SDK 15.2.0
• A little bit about your response in (2) - you mentioned a serial bootloader. How does this work? I'll have to use this for now, as we are working on optimizing the Bluetooth antenna for phase 2, which is why we split into two phases. Could you elaborate a bit on the serial bootloader.

Thanks for the links and response. I'll check them out and reply in a few days,

/Tim

[mrono]

In step 6 you should also include the softdevice hex file. Then you should have a complete image that can be flashed in one go.

[Edvin]

Hello,

You can merge all the hex files and program them in one go. That shouldn't be a problem.

Are you still working on the serial bootloader? Again, I have to say that if you intend to use the BLE bootloader in the end, it is easier to work with the BLE bootloader. If anything, it will advertise as "DfuTarg" if there is something wrong with the bootloader settings, so you should know that something is working.

If you don't use the softdevice in your bootloader, you still need the MBR. It is found in SDK\components\softdevice\mbr\nrf52840\hex\mbr_nrf52_2.4.1_mbr.hex.

merge this with your bootloader.

 

Tim Adu said:

How do I debug this? (I need to generate an image that can be flashed at the factory, so it cannot be a dfu package)

 It is a bit tricky to debug the bootloader project, because turning off optimization makes the project too big for the size limit of the flash area (since the bootloader is placed near the end of the flash, unlike a normal application that will typically start at the start of flash.

 

Tim Adu said:

When flashing the device, should it be done in stages (bootloader first, and then application), or can I merge the bootloader and application into a single image and flash that instead?

 That is not a problem. You should be able to merge everything and flashing it as one .hex file. Remember to reset the device after it is programmed. Either power cycle it, or run "nrfjprog --reset".

If you need to debug, then you must use the project that is called ..._debug, e.g. the SDK\examples\dfu\secure_bootloader\pca10056_ble_debug. This bootloader takes up a bit more space, and is placed a bit further down in the flash, so there is room for both debugging (step through without optimization turned on) and logging. 

If you generated the dfu image with the same key as you used in your bootloader (private_key->image, public_key->bootloader project), then it should jump to the application if these are programmed:

MBR or softdevice
Application
Bootloader
Bootloader settings.

I suspect that you were missing the MBR. Try to program that as well and see if the application starts up.

Best regards,

Edvin

[Tim Adu]

Alright. I finally have time to do this. I'm dedicating this week to get this to work.
Thanks for your previous reply.

1. Could I also just merge the MBR with the image and flash the output image as a single hex file?
2. Do these hex images need to be merged in any particular order?
3. When I try merging the Bootloader (+settings), Application, MBR and Softdevice, I get an error - "the hex file cannot be merged since there are conflicts". How can I determine the conflict source?

And FYI, I'm going for the BLE bootloader 
Thanks

Tim

[Edvin]

The conflicts are probably because you try to merge MBR and the softdevice. The MBR is already included in the Softdevice, so you don't need both.

Try to merge the softdevice, application and bootloader (+Settings). There shouldn't be any conflicting areas there.

BR,

Edvin

[Tim Adu]

Alright, so I tried merging in this order:

1. Bootloader and bootloader settings => OK
2. Merged bootloader and Application => OK
3. Application (+Bootloader +Settings) and Softdevice => FAIL

1. Do I have to change the start address of any of the components, or is this handled by the mergehex utility?

2. Is the merge order relevant?

3. My application currently doesn't include the SoftDevice. For now it's a completely "bluetooth-less" application. Could this be an issue?

Here are my hex files:

app.hex

7043.bootloader_settings.hex

secure_ble_s140_bootloader.hex

s140_nrf52_6.1.0_softdevice.hex

Thanks

Tim

[Edvin]

Hello Tim,

Your app.hex looks a bit strange. 

Does your app use the softdevice? 

The app.hex, does that come from when you compiled the application, or did you do a flash dump after programming it? The reason I ask is that when I watch your app.hex with nRF Connect -> Programmer it looks like this:

So the application has not put aside any space for the softdevice, which should be on the bottom/start. In addition, there is something in the top/end of the flash. what is that?

Does your application work if you program only app.hex and softdevice? It probably will not, because it doesn't have space for the flash, but what I mean is that it will not work to merge them if you can't flash both simultaneously.

So basically, you need to make your application work while you set aside space for the softdevice. Please refer to one of the ble_peripheral examples and the flash settings. If you are unsure on how to do that, please let me know what IDE you use, and I can give you some pointers.

BR,

Edvin

[Tim Adu]

Well I think I almost figured it out. This  tutorial was super helpful:

https://devzone.nordicsemi.com/nordic/short-range-guides/b/getting-started/posts/adjustment-of-ram-and-flash-memory

I had to change the start address of the application and integrate the softdevice into my application.

I managed to merge all files successfully, but the application still does not start. I used nRF Connect to watch my new image like you illustrated above and it looks as expected, based on the memory map described here: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.2.0/lib_bootloader.html

app_production_image.hex

(See the attached hex file).

Right now the softdevice is integrated in the application, but not initialized (as I mentioned in the beginning, we are not implementing any BLE features for now).

• Any ideas on why the application still does not start?

• Here are the contents of the bootloader settings:

Bootloader DFU Settings:
* File:                     ns_bootloader_setting.hex
* Family:                   NRF52840
* Start Address:            0x000FF000
* CRC:                      0x48172AA9
* Settings Version:         0x00000001 (1)
* App Version:              0x00000000 (0)
* Bootloader Version:       0x00000000 (0)
* Bank Layout:              0x00000000
* Current Bank:             0x00000000
* Application Size:         0x0001F688 (128648 bytes)
* Application CRC:          0x05F5197F
* Bank0 Bank Code:          0x00000001
* Softdevice Size:          0x00000000 (0 bytes)
* Boot Validation CRC:      0x00000000
* SD Boot Validation Type:  0x00000000 (0)
* App Boot Validation Type: 0x00000000 (0)

It says the sSoftDevice size is 0 bytes! I find that a bit odd. What do you think?

Thanks

Tim

[Edvin]

Tim Adu said:

It says the sSoftDevice size is 0 bytes! I find that a bit odd. What do you think?

 That should be fine. It says when I generate the bl_settings here as well.

Does the application start if you flash only the bootloader + SD, and then you upload the application via DFU using nRF Connect?

BR,

Edvin

[Tim Adu]

What I need now is for the bootloader to load the applicaton without having to do DFU/OTA update.

I just read this thread:
https://devzone.nordicsemi.com/f/nordic-q-a/19068/uploading-application-and-bootloader-application-not-starting

So I'm guessing my device is stuck in bootloader mode.

How can I force the bootloader to load the application?

Also, I read this line in nrf_bootloader_app_start.c:

uint32_t start_addr = MBR_SIZE; // Always boot from end of MBR. If a SoftDevice is present, it will boot the app.

"if a softdevice is present, it will boot the app." How do we ensure that either the MBR or softdevice boots the application?

Thanks

Tim

[Edvin]

Tim Adu said:

What I need now is for the bootloader to load the applicaton without having to do DFU/OTA update.

 I understand, but I am trying to rule out mistakes. Maybe you have not generated the keys correctly.

Let me try another way, then.

Have you done any changes to the bootloader project? What bootloader project did you start with? the pca10056_ble_debug or pca10056_ble?

What nrfutil command did you use to generate the bootloader settings?

Did you use the corresponding public and private key in the bootloader and bootloader settings, respectively?