About

This repository contains my work on programming the STM32 Cortex M4 microcontroller from the ground up. Instead of using pre-built libraries like STM32 HAL or CMSIS, I'm manually setting up registers, configuring clocks, and developing my own hardware abstraction layer (HAL) to interact with peripherals. This project aims to gain a deeper understanding of the microcontroller's architecture and low-level operations, with a focus on performance optimization and control.

Usage

Under Developement. However, you can check the example folder for each peripheral already implemented.

Makefile

Each folder has its own makefiles. One problem I encountered initially was my makefile not properly formatted, this can be checked by issuing cat -e -t -v <makefile_name>. The output will have $ denoting line endings and ^I indicating tab.

Debuging Using OpenOCD

Debugging is done with the help of OpenOCD. Two scripts are provided:

• flash.cfg
• debug.cfg

The scripts above can be used in different scenarios listed above:

1. Changes to source files would required rebuilding and flashing the target. The script from above have been incorporated into the makefile and a typical process would look like.

   cd ESA/multistage-boot/examples/<directory>
   make clean
   make
   # Make sure your device is connected at this point
   make flash
   make debug

2. No changes but a new board to be flashed, the process would look like

   cd ESA/multistage-boot/examples/<directory>
   # Make sure your device is connected at this point
   make flash
   make debug

   or

   cd ESA/multistage-boot/
   openocd -f flash.cfg
   openocd -f debug.cfg

3. Simple debugging

   cd ESA/multistage-boot/
   openocd -f debug.cfg

Once the debug server is started and listening for connections on the tcp port, use the arm-none-eabi-gdb to connect. Since it is a multistage boot system, the symbol files for both bootloader and application are loaded individual:

arm-none-eabi-gdb -q /home/aaminu/ESA/multistage-boot/build/_bootloader.elf
(gdb) target extended-remote localhost:3333
(gdb) load
(gdb) add-symbol-file /home/aaminu/ESA/multistage-boot/build/app.elf 0x8004000
# Answer y to the prompt

# Set the breakpoint, example below
(gdb) b main
(gdb) continue

# After breakpoint is reached, I like to use the layout to see where in the sorce code I am
(gdb) layout src
# Step through as you wish inspecting symbols and registers

Furthermore, one can connect to the openocd server by using the following commands and inspect the target device:

```bash
telnet localhost 4444
> init
> halt
> flash probe 0
> flash info 0
> flash erase_sector 0 0 <number of sector>
> flash write_image <path/to/image.bin> <start address>
```

Finally, openocd path is located at /usr/share/openocd/

Credits

• Embedded System Architecture - Dainele Lacamera
• controllerstech
• STM32 Board Specifications and Documentations