VSCode Cortex-Debugging

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Revision as of 17:27, 28 March 2022 by Jshankar (Talk | contribs) (Memory)

VSCode Cortex Debugging

Use F5 or the menu Run > Start Debugging to start a debug session:


This starts debug session. In case of troubles, check the Debug Console:

Reading symbols from arm-none-eabi-objdump.exe --syms -C -h -w E:\tm4c123gxl\blinky/build/blinky.elf
Reading symbols from arm-none-eabi-nm.exe --defined-only -S -l -C -p E:\tm4c123gxl\blinky/build/blinky.elf
Launching GDB: arm-none-eabi-gdb.exe -q --interpreter=mi2 "E:\\tm4c123gxl\\blinky/build/blinky.elf"
    Set "showDevDebugOutput": true in your "launch.json" to see verbose GDB transactions here. Helpful to debug issues or report problems
Launching gdb-server: openocd.exe -c "gdb_port 50000" -c "tcl_port 50001" -c "telnet_port 50002" -s "E:\\tm4c123gxl\\blinky" -f "c:/Users/shankarappa/.vscode/extensions/marus25.cortex-debug-1.4.0/support/openocd-helpers.tcl" -f board/ek-tm4c123gxl.cfg
    Please check TERMINAL tab (gdb-server) for output from openocd.exe
Finished reading symbols from objdump: Time: 843 ms
Finished reading symbols from nm: Time: 313 ms
C:\ProgramData\chocolatey\lib\gcc-arm-embedded\tools\gcc-arm-none-eabi-10-2020-q4-major\bin\arm-none-eabi-gdb.exe: warning: Couldn't determine a path for the index cache directory.
Reading symbols from E:\tm4c123gxl\blinky/build/blinky.elf...
0x0000031c in delayMs (n=500) at E:/tm4c123gxl/blinky/src/main.c:39
39	        for (j = 0; j < 3180; j++)
Program stopped, probably due to a reset and/or halt issued by debugger
SRST error
SRST error
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x00000354 msp: 0x2000021c
SRST error
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x00000354 msp: 0x2000021c
SRST error
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x00000354 msp: 0x2000021c
Note: automatically using hardware breakpoints for read-only addresses.

Temporary breakpoint 1, main () at E:/tm4c123gxl/blinky/src/main.c:16
16	    SYSCTL_RCGC2_R |= 0x00000020;

By default there are several debug views available. With the .svd file, we have access to the peripheral register too:


Debug Commands

There are the usual debug commands (continue, stepping, restart) plus a run and debug toolbar

  • Continue / Pause F5
  • Step Over F10
  • Step Into F11
  • Step Out Shift+F11
  • Restart Ctrl+Shift+F5
  • Stop Shift+F5

Assembly Stepping

Press CTRL+SHIFT+P to invoke command palette. Then Select Cortex-Debug:View Disassembly(Functon), type the function name you want to disassemble.

  1. 0x000002ac: 80 b5           	push	{r7, lr}
  2. 0x000002ae: 00 af           	add	r7, sp, #0
  3. 0x000002b0: 0e 4b           	ldr	r3, [pc, #56]	; (0x2ec <main+64>)
  4. 0x000002b2: 1b 68           	ldr	r3, [r3, #0]
  5. 0x000002b4: 0d 4a           	ldr	r2, [pc, #52]	; (0x2ec <main+64>)
  6. 0x000002b6: 43 f0 20 03     	orr.w	r3, r3, #32
  7. 0x000002ba: 13 60           	str	r3, [r2, #0]
  8. 0x000002bc: 0c 4b           	ldr	r3, [pc, #48]	; (0x2f0 <main+68>)
  9. 0x000002be: 0e 22           	movs	r2, #14
  10. 0x000002c0: 1a 60           	str	r2, [r3, #0]
  11. 0x000002c2: 0c 4b           	ldr	r3, [pc, #48]	; (0x2f4 <main+72>)
  12. 0x000002c4: 0e 22           	movs	r2, #14
  13. 0x000002c6: 1a 60           	str	r2, [r3, #0]
  14. 0x000002c8: 0b 4b           	ldr	r3, [pc, #44]	; (0x2f8 <main+76>)
  15. 0x000002ca: 0e 22           	movs	r2, #14
  16. 0x000002cc: 1a 60           	str	r2, [r3, #0]
  17. 0x000002ce: 4f f4 fa 70     	mov.w	r0, #500	; 0x1f4
  18. 0x000002d2: 00 f0 13 f8     	bl	0x2fc <delayMs>
  19. 0x000002d6: 08 4b           	ldr	r3, [pc, #32]	; (0x2f8 <main+76>)
  20. 0x000002d8: 1b 68           	ldr	r3, [r3, #0]
  21. 0x000002da: 07 4a           	ldr	r2, [pc, #28]	; (0x2f8 <main+76>)
  23. 0x000002dc: 03 f0 f1 03     	and.w	r3, r3, #241	; 0xf1
  24. 0x000002e0: 13 60           	str	r3, [r2, #0]
  25. 0x000002e2: 4f f4 fa 70     	mov.w	r0, #500	; 0x1f4
  26. 0x000002e6: 00 f0 09 f8     	bl	0x2fc <delayMs>
  27. 0x000002ea: ed e7           	b.n	0x2c8 <main+28>
  28. 0x000002ec: 08 e1           	b.n	0x500
  29. 0x000002ee: 0f 40           	ands	r7, r1
  30. 0x000002f0: 00 54           	strb	r0, [r0, r0]
  31. 0x000002f2: 02 40           	ands	r2, r0
  32. 0x000002f4: 1c 55           	strb	r4, [r3, r4]
  33. 0x000002f6: 02 40           	ands	r2, r0
  34. 0x000002f8: fc 53           	strh	r4, [r7, r7]
  35. 0x000002fa: 02 40           	ands	r2, r0

It is possible to set breakpoints in the assembly code, but one cannot see high level (C/C++) side-by-side with the assembly code. And the disassembly view does not show any more information or symbolic as the Eclipse CDT disassembly view does.


To view memory, use the Command Palette (CTRL+SHIFT+P) with Cortex-Debug:View Memory.


Then specify the expression for the memory location and a length.