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

Vscode-cortex-debug-run-menu.png

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

Debug Console Output

Launching GDB: /opt/toolchains/gcc-arm-none-eabi-10.3-2021.10/bin//arm-none-eabi-gdb -q –interpreter=mi2 /home/jshankar/codeprojects/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

Reading symbols from /home/jshankar/codeprojects/tm4c123gxl/blinky/build/blinky.elf…

Launching gdb-server: /usr/bin/openocd -c “gdb_port 50000” -c “tcl_port 50001” -c “telnet_port 50002” -s /home/jshankar/codeprojects/tm4c123gxl/blinky -f /home/jshankar/.vscode/extensions/marus25.cortex-debug-1.2.0/support/openocd-helpers.tcl -f board/ek-tm4c123gxl.cfg

Please check TERMINAL tab (gdb-server) for output from /usr/bin/openocd

0x00000000 in g_pfnVectors ()

Program stopped, probably due to a reset and/or halt issued by debugger

2

adapter speed: RCLK – adaptive

target halted due to debug-request, current mode: Thread 

xPSR: 0x01000000 pc: 0x00000354 msp: 0x2000021c

adapter speed: RCLK – adaptive

target halted due to debug-request, current mode: Thread 

xPSR: 0x01000000 pc: 0x00000354 msp: 0x2000021c

adapter speed: RCLK – adaptive

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 /home/jshankar/codeprojects/tm4c123gxl/blinky/src/main.c:16

16     SYSCTL_RCGC2_R |= 0x00000020;

Vscode-cortex-debug-window.png

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

Vscode-cortex-debug-views.png

Debug Commands

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

Vscode-cortex-debug-toolbar.png
  • 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 the command palette. Then Select Cortex-Debug:View Disassembly(Function), 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>)
  22.  
  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.

Memory

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

Vscode-cortex-debug-view-memory-menu.png

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

Vscode-cortex-debug-view-memory.png
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