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StealthChanger toolheads

The Voron 2.4 in this fleet runs the StealthChanger toolchange mechanism with 5 toolheads controlled by the viesturz/klipper-toolchanger Klipper extra.
Platform Voron 2.4
Toolboard RP2040-based, one per tool
Host Recore A7
Toolchanger plugin viesturz/klipper-toolchanger (upstream, unmodified)
NFC reader One PN532 (USB-UART) shared across all 5 tools, scanned spools assigned via multi-tool prompt

Topology

flowchart TB
    Recore["Recore A7<br/>Linux host"]
    USB["USB hub<br/>(VIA Labs)"]
    Recore --- USB
    USB --- T0[T0<br/>RP2040]
    USB --- T1[T1<br/>RP2040]
    USB --- T2[T2<br/>RP2040]
    USB --- T3[T3<br/>RP2040]
    USB --- T4[T4<br/>RP2040]
    USB --- NFC[PN532 reader]

    Recore -->|Klipper MCU protocol| T0
    Recore -->|Klipper MCU protocol| T1
    Recore -->|Klipper MCU protocol| T2
    Recore -->|Klipper MCU protocol| T3
    Recore -->|Klipper MCU protocol| T4

Why this stack

  • klipper-toolchanger handles the dock/undock kinematics, per-tool offsets, and the T0..T4 GCode contract.
  • NFC daemon's multi-tool mode populates per-tool save_variables (nfc_t0_* … nfc_t4_*) on each spool scan; the print-start macro reads those to set temps, PA, and any other per-filament parameters.
  • The combination means a tool can be swapped (mechanically or spool-wise) and the printer knows what to do without operator intervention beyond "tap the spool".

Known issues / things worth knowing

Toolchange Y clearance

Tools currently ram into adjacent docks under some macro variants — the close_y parameter is too small. Pending fix; increase close_y per viesturz/klipper-toolchanger docs when re-tuning the dock positions.

USB enumeration on power cycle

The VIA Labs hub has been observed to fail to re-enumerate one of the toolboards (retool1) after a power cycle. Root cause was firmware-version drift between toolboards. Mitigation: flash every RP2040 to the same firmware version in one batch before re-powering the printer. See How-to: flash RP2040 toolheads.

make flash on VIA Labs hub

The Klipper make flash command intermittently fails to write through the hub. Use the manual mount-and-copy approach (mount the RP2040 as USB mass storage, cp build/out/klipper.uf2 /mnt/rp2040/) rather than fighting make flash. Detailed in the flashing how-to.

Pressure advance per filament

When a spool is scanned, the NFC daemon writes the spool's tuned pressure advance from Spoolman into nfc_t{N}_pressure_advance (one key per tool). The fleet's canonical PA-apply macros — _PA_DEFAULTS (data macro of per-material fallbacks) and NFC_APPLY_PA (three-tier-priority applier) — are documented verbatim at save_variables → reading from macros. That page shows the single-tool form running on the Trident; on the StealthChanger Voron the same shape extends to per-tool variants:

  • Call NFC_APPLY_PA (or a _T{N} variant) once per tool inside the toolchanger's POST_TOOL_CHANGE hook so the picked-up tool's PA is set immediately after a swap.
  • Seed every tool at the top of PRINT_START so first-layer extrusion on the initial tool gets the right value.

Spoolman's per-spool nozzle-specific pressure-advance extra (e.g. nozzle_0_4_pressure_advance) stores the tuned value; the daemon copies it to save_variables on every scan so a freshly tuned PA in Spoolman propagates the moment that spool is loaded.

Host: Recore A7

See Recore (A6/A7/A8) — short answer is "Linux SBC with onboard stepper drivers; runs Klipper natively." Board-specific docs live on the iAgent wiki.