Difference between revisions of "PineTime bootloader improvements"
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(Add section "Why not add OTA functionality to the bootloader ?") |
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If the image is hard-coded, you won't be able to easily (not that easy, actually...) customize the boot logo. But remember that this logo is only display for a short time only when the device reset (manually or during an OTA). | If the image is hard-coded, you won't be able to easily (not that easy, actually...) customize the boot logo. But remember that this logo is only display for a short time only when the device reset (manually or during an OTA). | ||
=== Why not add OTA functionality to the bootloader ? === | |||
This is exactly how the NRF bootloader/SoftDevice works: the bootloader is a standalone firmware that provides OTA functionality thanks to the SoftDevice. The downside is that the BLE stack needed to provide OTA is quite big and uses a lot of space in flash memory (~124kB according to the documentation). This is roughly 1/4 of the available space in the internal flash memory. | |||
Firmware based on the NRF SoftDevice share the BLE stack with the bootloader, it is mutualised between both entities. | |||
The downside of this design is that firmwares developers are somewhat forced to use the NRF BLE stack. If they want to integrate another BLE stacak (NimBLE for example), these 120kB used by the SoftDevice would be wasted. | |||
That's why we decided to make the MCUBoot bootloader a simple bootloader without OTA functionality. It's very lighweight (less than 20kB) and leaves the developers the right to choose the BLE stack they want. | |||
=== Fixed vs dynamic memory map === | === Fixed vs dynamic memory map === | ||