Lup Yuen Lee 李立源 @lupyuen@qoto.org

Some parts of #BL602 Bootloader are located in ITCM Cache Memory (instead of XIP Flash) ... Maybe that's why the Bootloader is able to overwrite itself in XIP Flash Memory 🤔

https://github.com/lupyuen/bl_iot_sdk/releases/download/v8.0.2/bl602_boot2.map

Linker Script for #BL602 Bootloader says that some System Functions will be placed in ITCM (0x2201 0000) ... Like Global Register (GLB), Power (PDS), XIP Flash and eFuse 🤔

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2_flash.ld#L67-L95

#BL602 Application Firmware also has a Table of ROM API Functions ... But it's located at 0x4200 C000 (DTCM) 🤔

https://github.com/lupyuen/bl_iot_sdk/releases/download/v8.0.1/sdk_app_blinky.map

#BL602 Bootloader has a Table of ROM API Functions at 0x2201 0000 (ITCM) ... How is this table used? 🤔

https://github.com/lupyuen/bl_iot_sdk/releases/download/v8.0.2/bl602_boot2.map

Matching the #BL602 Bootloader Code ... With the Partition Table that's flashed to BL602 🤔

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2.c#L226-L269

Where does #BL602 Bootloader get the AES Encryption Key? From the eFuse Hardware!

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_port.c#L184-L209

#BL602 Bootloader writes Application Firmware to XIP Flash Memory

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2.c#L226-L269

#BL602 Bootloader installs the Application Firmware

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2.c#L271-L313

How #BL602 Bootloader starts the Application Firmware

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2.c#L509-L571

#BL602 Bootloader installs the Application Firmware ... With eFuse Protection (optional)

https://github.com/lupyuen/bl_iot_sdk/blob/master/customer_app/bl602_boot2/bl602_boot2/blsp_boot2.c#L381-L507

Quick check of #BL602 Boot2 Disassembly ... To be sure that it matches the Boot2 Bootloader that we have been flashing to BL602. Great exercise for learning #RISCV Assembly! 👍

https://github.com/lupyuen/bl_iot_sdk/releases/download/v8.0.2/bl602_boot2.S

When #BL602 boots, it runs the Boot2 Bootloader Firmware at 0x2300 0000 ... Which loads the Application Firmware into (yikes!) 0x2300 0000 ... Let's investigate how the Bootloader makes this self-overlay possible

https://github.com/lupyuen/bl_iot_sdk/blob/master/tools/flash_tool/bl602/builtin_imgs/blsp_boot2.map#L6884

#BL602 Linker Map shows Boot2 Code is always loaded at 0x2300 0300 ... Let's find out what's inside

https://github.com/lupyuen/bl_iot_sdk/releases/download/v8.0.1/sdk_app_blinky.map

My hunch: #BL602 Boot2 and ESP32 Secure Boot V2 have similar bootloader features 🤔

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/security/secure-boot-v2.html

#BL602 "Boot2" ... The Boot Code that starts every BL602 Firmware ... Shall I unravel and document the code? 🤔

https://github.com/bouffalolab/bl_iot_sdk/tree/master/customer_app/bl602_boot2/bl602_boot2

"The #RISCV #BL602 Book" ... Everything about BL602 spanning 18 articles ... And still growing! 👍

https://lupyuen.github.io/articles/book

uLisp for #PineTime Smartwatch? 🤔

https://www.reddit.com/r/PINE64official/comments/nm70kz/simulate_riscv_bl602_with_webassembly_ulisp_and/?utm_medium=android_app&utm_source=share

Ah Heng Chicken Curry Bee Hoon Mee (Michelin Recommended)

https://danielfooddiary.com/2019/03/07/ahheng/

Here's why our #BL602 Simulator runs a stream of Simulation Events

https://lupyuen.github.io/articles/wasm?20#why-simulate-a-stream-of-events

Will our #BL602 Simulator run Actual BL602 Firmware in #WebAssembly? It might be possible!

https://lupyuen.github.io/articles/wasm?19#can-we-simulate-any-bl602-firmware