blinky_led_freeRTOS

Basic LED blinky project using FreeRTOS on STM32L476 MCUs.

• 2 tasks with equal priority toggle an LED on and off.
• No CMSIS used for in-depth learning about FreeRTOS use with Cortex-M MCUs.

Features:

• HardFault debugging handler
• Timer2 blocking and non-blocking delays
• Easy to adapt and configure for a new project with more source and header files!

Usage Guide (requires OpenOCD and Arm-GNU toolchain):

Build as-is:

make
make install

Use HardFault debugging to find cause of the Hard Fault:

1. Create memory debug files

make symbols
make dump

-> this creates two files in the folder memory_debug:

• disassembly.txt - contains raw memory and instructions of the application
• symbols.txt - contains the symbol table of the application

2. Check where the program counter (pc) was at when the Hard Fault occurred:

• search for pc in symbols.txt: this will give you the memory address of pc, which we will call pc_address

3. Run a gdb server/client to check what address pc holds during the Hard Fault:

• run the load and client commands in separate terminals:

make load
make client
    target remote localhost:3333
    monitor reset init
    monitor flash write_image erase final.elf
    monitor reset halt
    monitor resume
    monitor mdw 0xpc_address 1

-> this will return the address that pc contained when the Hard Fault occurred, which we will call hardfault_address.

4. Find the hardfault_address in disassembly.txt by searching for the 6 nibbles in the middle of hardfault_address

• i.e., if hardfault_address = 08001049, then you would search for 800104 in disassembly.txt.

5. This much information should allow you to figure out the root cause of the Hard Fault.

• i.e., if you have a misaligned address (like the example above), then you can find which function/IRQ_Handler caused that issue and go from there.