AVR Assembly Compiler & Debugger

This is a simple Bash script to compile and debug AVR Assembly .asm files using avr-gcc, simavr, and avr-gdb. It supports the ATmega328P microcontroller and can display the LCD output in the GDB terminal.

---

🛠 Requirements

Clone this repository with

git clone https://github.com/Dzendys/AVR.git

The repository will be cloned into a subdirectory named AVR within your current terminal working directory.

Before using the script, install the necessary tools:

sudo apt install binutils-avr gcc-avr avr-libc gdb-avr simavr

💡 Assembly format

Your .asm file should follow this format:

.text
.global main

main:
    ; your AVR assembly code here

loop:
    nop
    jmp loop

.end

You can try and modify the example.asm code in this repository.

🖥️ LCD Display

Make sure to include the printlib.inc (keep the version in the repository, as using a different one might cause issues).

To display characters on an LCD screen, first call the init_disp function to initialize the display. Then, you can use the show_char function to display a character at a specified position. The character is passed in R16, and the position is determined by R17.

.text
.global main
.include "printlib.inc"

main:
    call init_disp
    ldi r16, 'A'
    ldi r17, 0
    call show_char

loop:
    nop
    jmp loop

.end

The LCD display has two lines, with the first line displaying characters at positions 0x00 to 0x0F and the second line at positions 0x40 to 0x4F.

🚀 Usage

Go to your terminal and type:

./run_avr.sh <your_file.asm>

Make sure, you have execution permissions. If not, add them by chmod u+x run_avr.sh.

The script checks for the .asm extension, changes extention to .S, compiles it to an .elf binary, and starts simavr on localhost:1234.

Then it launches avr-gdb with a TUI interface for debugging. Additionally, it runs the lcd_display.gdb script which shows the LCD output in the GDB terminal.

Compilation errors will abort the script.

Temporary .S and .elf files are automatically deleted when you exit the debugger.

📸 Screenshot

📜 License

No license. Use and modify freely. Credit and pull requests are appreciated.

❓ FAQ

1. Why do I need to import printlib.inc when it only contains a ret instruction?
   It's required to ensure compatibility with the MPLAB library used in the BI-SAP course. Additionally, it serves as a "hook" for GDB, allowing you to set breakpoints and monitor the display output.

2. Why does the program stop at show_char when I use continue?
   This is because a breakpoint is set in GDB at show_char to print the LCD display at the correct moment.

3. Why is the printlib so limited? And why isn’t there a separate function for saving and displaying characters on the LCD?
   The printlib is designed to have the same interface as the one used in MPLAB for the BI-SAP course. This ensures compatibility with their code, which is why it's kept simple and not split into separate functions for saving and displaying characters.

4. Does the program support buttons?
   No, it doesn't support buttons yet. Work is ongoing to add this feature in the future.

5. Why does the lcd_display.gdb script look messy?
   AVR-GDB is very limited in functionality, and this is currently the most readable code that can be written given the available features.

6. Does it work on Windows?
   Yes, it works on Windows through WSL (Windows Subsystem for Linux).

7. Why am I getting a "Compilation error" when it works in MPLAB?
   This is likely because you skipped the README and didn’t realize that the sections syntax is different. For example, .org and other directives are not supported in the same way here. I recommend writing the code in example.asm where the sections are set up correctly.

8. Why can’t I run the script?
   Make sure the script is up to date with the latest version from the repository and that it has the correct line endings (LF/CRLF).

If you encounter additional errors, please report them in Issues or write me on Discord (@dzendys_).

"MPLAB je sračka." - Sun Tzu