VSCode Cortex Debugging

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

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

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;

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 the command palette. Then Select Cortex-Debug:View Disassembly(Function), type the function name you want to disassemble.

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