can't get rid of "error:79" on first dry run

Short story: Cannot issue a $X on a dry run of my first own grbl-hal build. Always get "error:79"

Details:

Try to setup a lathe controller on a blackpill.
STM32CubeIDE, flash with a st-Link clone
Test with GtkTerm connecting to /dev/ttyACM0
no hardware connected to any pin

Finally, I manged to talk to the thingie:

$I
[VER:1.1f.20240709:]
[OPT:VNMDSL+,100,1024,3,0]
[AXS:3:XYZ]
[NEWOPT:ENUMS,RT+,HOME,ES,SS,SED]
[FIRMWARE:grblHAL]
[SIGNALS:HSDEP]
[NVS STORAGE:*FLASH]
[FREE MEMORY:92K]
[DRIVER:STM32F411]
[DRIVER VERSION:240624]
[BOARD:BlackPill Lathe]
[AUX IO:0,4,0,0]
[PLUGIN:Bootloader Entry v0.02]
[PLUGIN:MODBUS v0.16]

Following https://github.com/grblHAL/core/wiki/First-Run-Grbl-Settings and some educated guess, I inverted all inputs until I get an empty pin report in the status line:

$14=78
$5=7
$6=1

?<Alarm|MPos:0.000,0.000,0.000|Bf:100,1024|FS:0,0>

$G
[GC:G0 G54 G17 G21 G90 G94 G49 G98 G50 M5 M9 T0 F0 S0.]

$X
error:79

I miss the lathe commands (G7, G8, G33, G76, G95, G96, G97) I assume this may be that in the "Alarm" state, the parser is not "armed" to read those.

I can't find any documentation about "errror:79" - nor in the web nor int grbl-hal's github. Or is it a combination of "error 7 = open safety door" "error 9 = homing failed"?

========

update:

More by luck than by knowledge, I finally found it:

ctrl+X is not the same as $X
after cleaning all ports by inverting them, i did

<ctrl+x>
GrblHAL 1.1f ['$' or '$HELP' for help]
[MSG:'$H'|'$X' to unlock]
ok

$X
[MSG:Caution: Unlocked]
ok

$G
[GC:G0 G54 G17 G21 G90 G94 G49 G98 G50 M5 M9 T0 F0 S0.]
ok

G0 X4
ok 

?
?<Idle|MPos:4.000,0.000,0.000|Bf:100,1024|FS:0,0|Ov:100,100,100|H:0>

I'll leave the message just in case sbdy else stucks at the same point... Now at least the error message upon G33 changes to error:2

which tells me I have to continue testing, I think.

grblHAL / core

can't get rid of "error:79" on first dry run #548