`save_variables` keys¶

Every key the NFC daemon writes via SAVE_VARIABLE, with type, source, and consumer.

Backed on real Klipper by [save_variables] (file on disk), on the bridge by the persistent DB's save_variables namespace.

Single-tool mode¶

Key	Type	Source	Consumed by
`nfc_spool_id`	int	Spoolman `/api/v1/nfc/lookup`	`PRINT_START`, debug
`nfc_filament_id`	int	Spoolman spool detail	reference
`nfc_filament_name`	string	Spoolman `filament.name`	UI, debug
`nfc_material`	string	Spoolman `filament.material`	conditional logic in `PRINT_START`
`nfc_vendor`	string	Spoolman `filament.vendor.name`	UI, debug
`nfc_color_hex`	string	Spoolman `filament.color_hex`	LED/UI
`nfc_diameter`	float	Spoolman `filament.diameter`	extruder rotation_distance sanity check
`nfc_extruder_temp`	int	Spoolman `filament.settings_extruder_temp`	`M109` in `PRINT_START`
`nfc_bed_temp`	int	Spoolman `filament.settings_bed_temp`	`M190` in `PRINT_START`
`nfc_pressure_advance`	float	Spoolman `extra.nozzle_<size>_pressure_advance`	`SET_PRESSURE_ADVANCE` in `PRINT_START`

Multi-tool mode¶

Same keys, with nfc_t{N}_ prefix per tool index. Example for T2:

Key	Type	Notes
`nfc_t2_spool_id`	int
`nfc_t2_filament_id`	int
`nfc_t2_filament_name`	string
`nfc_t2_material`	string
`nfc_t2_vendor`	string
`nfc_t2_color_hex`	string
`nfc_t2_diameter`	float
`nfc_t2_extruder_temp`	int
`nfc_t2_bed_temp`	int
`nfc_t2_pressure_advance`	float	per-nozzle from Spoolman extras

Up to whatever tool count your printer has (tools = … in nfc_spoolman.cfg).

Reading from macros¶

The canonical pattern¶

The fleet's actual approach factors the read into two macros:

_PA_DEFAULTS — a data-only macro that stores per-material fallback values. Empty gcode body; the variables are the payload.
NFC_APPLY_PA — a call macro that applies pressure advance with a three-tier priority:
Spool-specific value from the last NFC scan (nfc_pressure_advance > 0)
Per-material fallback from _PA_DEFAULTS if the spool didn't have a tuned PA
Universal default if neither is set

NFC_APPLY_PA is called from PRINT_START after the spool data has been loaded by the NFC daemon.

The actual macros (Voron Trident 300)¶

# ─────────────────────────────────────────────────────────────────────────────
# PA DEFAULTS — per-material fallback values used when a spool has no
# tuned PA stored in Spoolman. Edit these to match your measured defaults.
# Values here should be conservative (slightly high is better than too low).
# ─────────────────────────────────────────────────────────────────────────────

[gcode_macro _PA_DEFAULTS]
description: Per-material Pressure Advance fallback values (data macro, not called directly)
variable_pla:     0.040
variable_petg:    0.065
variable_asa:     0.035
variable_abs:     0.035
variable_tpu:     0.000
variable_pc:      0.040
variable_pa_nylon: 0.040
variable_default: 0.040
gcode:
    # Intentionally empty — this macro is a data store only.
    # Call NFC_APPLY_PA to apply the appropriate value.


# ─────────────────────────────────────────────────────────────────────────────
# NFC_APPLY_PA — apply Pressure Advance from the last NFC scan.
#
# Priority order:
#   1. nfc_pressure_advance > 0 in saved variables  -> use spool-specific value
#   2. nfc_material is a known material              -> use _PA_DEFAULTS value
#   3. Neither                                       -> use _PA_DEFAULTS.default
# ─────────────────────────────────────────────────────────────────────────────

[gcode_macro NFC_APPLY_PA]
description: Apply Pressure Advance from NFC spool data, with per-material fallback
gcode:
    {% set svv = printer.save_variables.variables %}
    {% set pa_stored = svv.nfc_pressure_advance | default(-1.0) | float %}
    {% set material  = svv.nfc_material          | default("")  | string | upper %}
    {% set defaults  = printer["gcode_macro _PA_DEFAULTS"] %}

    {% if pa_stored > 0 %}
        SET_PRESSURE_ADVANCE ADVANCE={pa_stored}
        RESPOND TYPE=echo MSG="NFC PA: {pa_stored|round(4)} (spool-specific, material: {material})"

    {% else %}
        {% if   material == "PLA"                    %} {% set pa_fb = defaults.pla      %}
        {% elif material == "PETG"                   %} {% set pa_fb = defaults.petg     %}
        {% elif material in ["ASA", "ABS"]           %} {% set pa_fb = defaults.asa      %}
        {% elif material == "TPU"                    %} {% set pa_fb = defaults.tpu      %}
        {% elif material == "PC"                     %} {% set pa_fb = defaults.pc       %}
        {% elif material in ["PA", "NYLON", "PA-CF"] %} {% set pa_fb = defaults.pa_nylon %}
        {% else                                      %} {% set pa_fb = defaults.default  %}
        {% endif %}

        SET_PRESSURE_ADVANCE ADVANCE={pa_fb}

        {% if material == "" %}
            RESPOND TYPE=echo MSG="NFC PA: {pa_fb|round(4)} (no material info - using default fallback)"
        {% else %}
            RESPOND TYPE=echo MSG="NFC PA: {pa_fb|round(4)} (material fallback for {material} - no spool-specific value)"
        {% endif %}
    {% endif %}

Drop this verbatim into printer.cfg (or an included file). Edit the variable_* defaults in _PA_DEFAULTS to match your tuned values per material. Call NFC_APPLY_PA from your PRINT_START:

[gcode_macro PRINT_START]
gcode:
    # …homing, levelling, heat soak, etc…
    NFC_APPLY_PA
    # …prime line, first layer, etc…

Multi-tool extension (Voron 2.4 / StealthChanger)¶

For a toolchanger the pattern extends to per-tool keys (nfc_t{N}_pressure_advance, nfc_t{N}_material). Apply once per tool — typically inside the toolchange POST_TOOL_CHANGE hook so the new tool's PA is loaded immediately after a swap, and once per tool at print-start to seed every tool's PA before the first extrusion.

The shape is the same NFC_APPLY_PA macro with nfc_pressure_advance and nfc_material swapped for the tool-indexed variants and the target extruder passed via SET_PRESSURE_ADVANCE EXTRUDER=…. See Toolchange workflow for the multi-tool shape.

Inspecting from CLI¶

# Real Klipper
cat ~/printer_data/config/saved_variables.cfg

# Either real Klipper or bridge
curl -s http://localhost:7125/printer/objects/query?save_variables \
    | jq '.result.status.save_variables.variables'

Clearing¶

A scanned spool overwrites the same keys, so unloading a spool doesn't auto-clear. To clear T2:

for k in spool_id filament_id filament_name material vendor color_hex \
         diameter extruder_temp bed_temp pressure_advance; do
    curl -X POST http://localhost:7125/printer/gcode/script \
        -d "script=SAVE_VARIABLE VARIABLE=nfc_t2_${k} VALUE=0"
done

(Or use NFC_CLEAR if you've added a macro for it — not shipped by default.)

save_variables keys¶