Re:I like the RP2040
by dgroshev on Tuesday June 11, 2024 @11:21AM
(#40647274)
You can have several bootloader stages, and in fact that's how the RP2040 works [1]!
Stage 1 bootloader is the one in ROM and it normally just reads stage 2 from the flash chip. Stage 2 then initialises the flash properly, and you can have further stages like [2] to implement the trial-rollback procedure.
Stage 1 is a safety net, even if the trial-rollback procedure goes terribly wrong the device can still be unbricked over USB.
Stage 1 bootloader is the one in ROM and it normally just reads stage 2 from the flash chip. Stage 2 then initialises the flash properly, and you can have further stages like [2] to implement the trial-rollback procedure.
Stage 1 is a safety net, even if the trial-rollback procedure goes terribly wrong the device can still be unbricked over USB.
[1]: https://blog.usedbytes.com/2021/12/pico-serial-bootloader/
[2]: https://embassy.dev/book/#_bootloader