RE: BLE Secure DFU Bootloader - Noob Doubts

tesc — Thu, 11 Oct 2018 11:01:11 GMT

Hi,

1. The size of the hex file is much larger than the actual size of the binary data, as it is an ASCII encoded version of the binary data including addresses, checksums and other commands in addition to the data itself. See the Intel HEX Wikipedia article for more information on the format of hex files, and for examples.

2. BL settings version is needed so that the bootloader knows the format of the settings page is correct. If it is different from what the bootloader expects then it will treat it as if it was empty.

For the other settings in 2., and for 3. and 4., I refer to the answers provided by WestCoastDaz. I might add for 4. that the inactivity timeout is used regardless of how you enter DFU mode.

Regards,
Terje

RE: BLE Secure DFU Bootloader - Noob Doubts

WestCoastDaz — Wed, 10 Oct 2018 17:56:39 GMT

Hi,

Here are the answers to most of your questions:

1. Sounds like you are building the debug version of the bootloader. The debug version enables all of the log statements which end up making the bootloader very large. That said from the image above it looks like you are using the hex file size which will always be large than a binary file given it's in ASCII and includes the metadata for address location.

2. Even if you don't plan on updating the bootloader or SD you need these regardless as the DFU will use some of them to ensure compatibility during a DFU. I don't believe there is a why to block bootloader or SD updates. Also in my experience being able to update the bootloader isn't something we planned on using either but it saved us in a recent project.

3. Have you looked at the ble_app_buttonless_dfu example? This details how to go about doing this. In my experience I don't like the fact that a write to flash is required every time I want to enter the bootloader so I use

NRF_BL_DFU_ENTER_METHOD_GPREGRET

4. Your understanding for boot is correct. The NRF_BL_DFU_INACTIVITY_TIMEOUT_MS is used to if you enter the bootloader from the application and no BLE activity is occurs within the timeout. Without this it would be possible to for your application to stay in the bootloader indefinitely if it was entered from the application.

Cheers!