How to write a bootloader from scratch (2019)

https://interrupt.memfault.com/blog/how-to-write-a-bootloader-from-scratch

by arkj • 4 years ago

189 19 4 years ago

interrupt.memfault.com

Koshkin• 4 years ago

(For a Cortex-M based microcontroller)

kaycebasques2• 4 years ago

(n00b q) are there big differences for Cortex-A and Cortex-M bootloaders? Any helpful tutorials for Cortex-A if so?

auxym• 4 years ago

Cortex-A appears to be way more vendor-implementation dependent. For example, I remember reading that the Raspberry Pi SoC, which uses a Cortex-A72 core, actually boots off its GPU.

megous3• 4 years ago

Yes. DRAM initiazization, MMU, exception levels, trusted-firmware, initialization of specialized coprocessors for system power states management, more complicated storage access options (SD card/eMMC), etc. etc.

fra2• 4 years ago

Yes, an important qualifier! In practice the vast majority of embedded projects out there are on cortex M, with a bit of xtensa (ESP32) and a bit of RISC-V.

chinabot• 4 years ago

and 32-Bit microprocessors are still only about 1/3 of total microprocessors by volume (source https://www.ednasia.com/8-bit-mcu-still-alive-and-kicking/)

hra5th• 4 years ago

For Cortex-M embedded topics, memfault's blog is simply one of the best out there. Consistently great posts even though they are written by a bunch of different authors. I go back to https://interrupt.memfault.com/blog/cortex-m-fault-debug all the time when debugging hard faults on different systems.

Even if you regularly write embedded code for Cortex-M MCUs, scroll through their list of posts and you'll find several that will teach you something new and useful.

RealityVoid• 4 years ago

I'm a bit jealous of the fact they have such good blog posts. I did a deep dive on a couple of different architectures and always wanted to write something so nice and useful for other people with the stuff I know.

dang• 4 years ago

From zero to main(): How to write a bootloader from scratch - https://news.ycombinator.com/item?id=24635383 - Sept 2020 (44 comments)

kaycebasques2• 4 years ago

The CMSIS-DAP adapter referenced in the tutorial is discontinued. Can one of you hardware pros point me to a suitable replacement?

Also asked the author here: https://mobile.twitter.com/kaycebasques/status/1585708384531...

codys• 4 years ago

Other CMSIS-DAP compatible probes:

- https://makerdiary.com/products/pitaya-link

- https://www.l-tek.com/web-shop/cmsis-dap-debug-probe/

fra2• 4 years ago

Author here. It's surprising how hard CMSIS-DAP adapters are to find. The two options shared by codys look reasonable, but I'm working on putting together a better option.

zwirbl• 4 years ago

I'm using https://github.com/probe-rs/hs-probe most of the time, sometimes I get out a jlink

scoutt• 4 years ago

We use these in production because the IO signals are buffered: https://www.artekit.eu/products/debug/ak-cmsis-dap/

joko42• 4 years ago

"Zero to main" is the best resource there is about writing bootloaders. Wrote my first boatloader with the help of this series.

How to write a bootloader from scratch (2019)

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