Drop-in replacement controller for the Langmuir Systems CrossFire CNC plasma table. Runs on an Arduino Uno with an Electronics-Salon screw terminal shield, fully compatible with Langmuir's FireControl sender software.
This project replaces the stock CrossFire controller board with commodity hardware while keeping the full FireControl experience — jogging, G-code streaming, torch control, pierce delay overrides, and THC support.
The CrossFire already has external Leadshine stepper drivers built into the electronics enclosure — the Arduino only needs to output 5V logic-level step/direction/enable signals. No motor driver shield (gShield, CNC shield, etc.) is required.
| Component | Purpose | Link | Approx Cost |
|---|---|---|---|
| Arduino Uno R3 | Motion controller (ATmega328P @ 16MHz) | Amazon | ~$25 |
| Electronics-Salon Screw Terminal Shield | Breakout for wiring to CrossFire drivers | Amazon | ~$8 |
| USB Cable (Arduino to PC) | For flashing firmware and connection | Included with Arduino | - |
Total: ~$33 (vs $200+ for a stock CrossFire replacement board)
This project uses the Electronics-Salon D-1229 screw terminal breakout shield, which gives you easy screw-terminal access to every Arduino Uno pin without soldering. (Amazon link)
The shield plugs directly onto the Arduino Uno. All connections below refer to the screw terminal numbers printed on the shield.
The CrossFire is a 2-axis (X/Y) plasma table. The Leadshine stepper drivers are already in the CrossFire's electronics enclosure — you just need to connect the 5V logic signals from the Arduino to the driver inputs.
Each axis needs three wires: STEP, DIR, and ENABLE.
LEADSHINE DRIVER (X) LEADSHINE DRIVER (Y)
┌──────────────┐ ┌──────────────┐
Terminal 2 ───►│ PUL+ (Step) │ Terminal 3 ──►│ PUL+ (Step) │
Terminal 5 ───►│ DIR+ (Dir) │ Terminal 6 ──►│ DIR+ (Dir) │
Terminal 8 ───►│ ENA+ (Enable)│ Terminal 8 ──►│ ENA+ (Enable)│
GND ───►│ PUL-/DIR-/ENA│ GND ──►│ PUL-/DIR-/ENA│
└──────────────┘ └──────────────┘
| Screw Terminal | Arduino Pin | GRBL Function | Wire To |
|---|---|---|---|
| 2 | D2 | X Step | X Leadshine driver PUL+ |
| 3 | D3 | Y Step | Y Leadshine driver PUL+ |
| 5 | D5 | X Direction | X Leadshine driver DIR+ |
| 6 | D6 | Y Direction | Y Leadshine driver DIR+ |
| 8 | D8 | Stepper Enable | Both drivers ENA+ (active low) |
| GND | GND | Ground | Both drivers PUL-/DIR-/ENA- |
Note: Terminal 8 (Enable) is shared — run a wire from terminal 8 to both the X and Y driver enable inputs. The enable signal is active-low: LOW = motors engaged, HIGH = motors released.
Completed wiring showing Arduino Uno with screw terminal shield connected to CrossFire Leadshine drivers
The torch fire signal uses the spindle enable pin. When FireControl sends M3 (spindle on), this pin goes HIGH to trigger the plasma cutter. The CrossFire's electronics enclosure already has a MOSFET/transistor circuit for torch triggering — connect pin 12 to the torch trigger input on the CrossFire's wiring harness.
| Screw Terminal | Arduino Pin | Function | Wire To |
|---|---|---|---|
| 12 | D12 | Torch Fire | CrossFire torch trigger input |
| GND | GND | Ground | CrossFire trigger ground |
| Screw Terminal | Arduino Pin | Function |
|---|---|---|
| 9 | D9 | X Limit |
| 10 | D10 | Y Limit |
| 11 | D11 | Z Limit |
| Screw Terminal | Arduino Pin | Function |
|---|---|---|
| A0 | A0 | Reset |
| A1 | A1 | Feed Hold |
| A2 | A2 | Probe |
| A5 | A5 | THC Enable Signal |
ELECTRONICS-SALON SCREW TERMINAL SHIELD
┌──────────────────────────────────────────────────────────┐
│ │
│ Terminal 2 ── X STEP ──────► X Leadshine PUL+ │
│ Terminal 3 ── Y STEP ──────► Y Leadshine PUL+ │
│ Terminal 5 ── X DIR ──────► X Leadshine DIR+ │
│ Terminal 6 ── Y DIR ──────► Y Leadshine DIR+ │
│ Terminal 8 ── ENABLE ──┬───► X Leadshine ENA+ │
│ └───► Y Leadshine ENA+ │
│ Terminal 12 ── TORCH ──────► CrossFire torch trigger │
│ Terminal A5 ── THC ──────► THC Module (optional) │
│ GND ────────────┬───► Leadshine PUL-/DIR-/ENA- │
│ └───► CrossFire trigger ground │
│ │
└──────────────────────────────────────────────────────────┘
There are two things to flash:
- USB firmware on the Uno's ATmega16U2 chip (one-time, makes FireControl recognize the device)
- GRBL firmware on the Uno's main ATmega328P chip (the actual motion controller)
FireControl checks the USB Vendor ID and Product ID before it will connect. A stock Arduino Uno identifies as VID 2341 PID 0043 — FireControl ignores this. You need to reprogram the Uno's ATmega16U2 USB interface chip to report as a Langmuir CrossFire device:
- Target VID:
16D0 - Target PID:
0EFB - Device Name: "Langmuir Systems CrossFire"
Different Arduino Uno revisions use different USB interface chips. This matters for flashing:
| Arduino Version | USB Chip | DFU USB PID | Hex File |
|---|---|---|---|
| Uno R2 (and earlier) | AT90USB82 | 03EB:2FF7 |
CrossFire-spoof-8u2.hex |
| Uno R3 | ATmega16U2 | 03EB:2FEF |
CrossFire-spoof-16u2.hex |
| Uno R3 (some clones) | ATmega8U2 | 03EB:2FEE |
CrossFire-spoof-16u2.hex |
| Chinese clones | CH340G | N/A | Cannot use DFU method |
Important: If your Arduino uses a CH340 USB chip (common on cheap clones), this method won't work. You need an Uno with an Atmel USB chip (ATmega16U2 or AT90USB82).
The ATmega16U2 is the small chip near the USB port on the Arduino Uno. To reprogram it, you need to put it into DFU (Device Firmware Update) mode:
-
Plug the Arduino into USB — it should be connected to your computer.
-
Locate the ICSP2 header — This is the 6-pin header closest to the USB port (not the one near the power jack).
-
Briefly short RESET to GND — Using a jumper wire or tweezers, momentarily connect the RESET pin to the GND pin on the ICSP2 header:
ICSP2 Header (near USB port): ┌───────────┐ │ MISO VCC │ │ SCK MOSI │ │ RST GND │ ◄── Short these two briefly └───────────┘ -
Verify DFU mode — The Arduino's COM port will disappear from Device Manager. Windows will detect a new USB device with Atmel's DFU VID (
03EB). The PID tells you which chip you have (see table above).
Windows doesn't have a built-in driver for the Atmel DFU device. You need Zadig to install one:
- Download Zadig
- Run Zadig, go to Options > List All Devices
- Select "Arduino Uno DFU" (or similar — look for VID
03EB) - Note the USB ID to identify your chip variant
- Select libusb-win32 as the target driver
- Click Install Driver (or Replace Driver)
Download dfu-programmer and extract it. On Windows, you'll have dfu-programmer.exe and libusb-1.0.dll.
On Linux/Mac:
sudo apt install dfu-programmer # Debian/Ubuntu
brew install dfu-programmer # macOSFor ATmega16U2 (Uno R3):
# Step 1: Erase the chip
dfu-programmer atmega16u2 erase
# Step 2: Flash the spoofed firmware (preserves DFU bootloader)
dfu-programmer atmega16u2 flash --suppress-bootloader-mem firmware/CrossFire-spoof-16u2.hex
# Step 3: Exit DFU mode and run new firmware
dfu-programmer atmega16u2 launchFor AT90USB82 (Uno R2):
dfu-programmer at90usb82 erase
dfu-programmer at90usb82 flash --suppress-bootloader-mem firmware/CrossFire-spoof-8u2.hex
dfu-programmer at90usb82 launchNote: The
--suppress-bootloader-memflag is important — it prevents overwriting the DFU bootloader itself, so you can reflash again in the future.
Not sure which chip? Try each target until one connects:
dfu-programmer at90usb82 get # Uno R2 (PID 2FF7) dfu-programmer atmega16u2 get # Uno R3 (PID 2FEF) dfu-programmer atmega8u2 get # Some boards (PID 2FEE)
If you have an AVR ISP MK2 or similar programmer, you can flash the USB chip directly via the ICSP2 header without using DFU mode:
# Backup existing firmware first
avrdude -p atmega16u2 -c avrispmkii -P usb -B 10 \
-U flash:r:usb-chip-backup.hex:i
# Flash spoofed firmware
avrdude -p atmega16u2 -c avrispmkii -P usb -B 10 \
-U flash:w:firmware/CrossFire-spoof-16u2.hex:iUnplug and replug the Arduino. It should now appear as:
- Windows Device Manager: "Langmuir Systems CrossFire" on a new COM port
- Linux:
lsusbshows16d0:0efb - Arduino CLI:
arduino-cli board listshows the new VID/PID
Reverting: To restore the original Arduino USB firmware, enter DFU mode again and flash the stock firmware from the Arduino IDE install directory (
hardware/arduino/avr/firmwares/atmegaxxu2/).
# Using arduino-cli (download from https://arduino.github.io/arduino-cli/)
arduino-cli upload -p COMxx --fqbn arduino:avr:uno --input-file firmware/grbl-ls-1.3ls.hexReplace COMxx with your actual COM port (check Device Manager).
avrdude -c arduino -p atmega328p -P COMxx -b 115200 -U flash:w:firmware/grbl-ls-1.3ls.hex:iRequires avr-gcc toolchain installed.
# Build
make
# Flash (uses avrisp2 programmer by default)
make flash
# Or specify Arduino bootloader programmer:
make flash PROGRAMMER="-c arduino -P COMxx -b 115200"- Open FireControl
- It should detect "CrossFire Gen 2" on the COM port
- Status bar shows connection and version 1.3ls
GRBL stores settings in EEPROM which persists across firmware updates. After flashing, you must reset to load the new firmware defaults:
In FireControl Console/Terminal, send:
$RST=$
Then power cycle the Arduino (unplug/replug USB).
Or manually set the key values:
$100=503.936 (X steps/mm for 8TPI)
$101=503.936 (Y steps/mm for 8TPI)
$3=3 (Invert X and Y for Mach3 wiring)
Verify settings loaded:
$$
Check that $100 and $101 show the correct steps/mm for your lead screws.
- Try jogging — if the motors move in the correct direction and distance, you're done
- If an axis moves backwards, flip the DIR wires on that stepper driver (or change
$3direction invert mask)
IMPORTANT: There are two firmware versions available depending on your CrossFire model and wiring:
- For newer CrossFire models with standard Langmuir wiring
- No axis direction inversion (
$3=0) - Use if your axes move correctly with the official Langmuir firmware
- For original Mach3-based CrossFire tables converted to grbl
- Inverts both X and Y axis directions (
$3=3) - Use if BOTH axes move backwards with standard firmware
How to tell which version you need:
- Flash the standard firmware first
- Test axis movement in FireControl:
- Press +X → should move RIGHT
- Press -X → should move LEFT
- Press +Y → should move AWAY (back)
- Press -Y → should move TOWARD you (front)
- If BOTH X and Y move in the wrong direction, use the inverted firmware
- If only ONE axis is wrong, check your wiring or use
$3settings to invert individual axes
Note: The original CrossFire tables that shipped with Mach3 control software typically require the inverted firmware due to different motor driver wiring conventions.
Important: The Arduino Uno has a maximum step rate of ~30,000 steps/second. This hardware limitation determines your actual maximum speed based on your lead screw configuration.
When you command a speed that exceeds the Arduino's step generation capability, the machine will simply move at the maximum achievable speed. For example:
- Commanding 120 IPM → Machine moves at 120 IPM ✓
- Commanding 200 IPM → Machine moves at ~120 IPM (hardware limit)
- Commanding 300 IPM → Machine moves at ~120 IPM (hardware limit)
All speeds above the limit result in the same actual speed — the hardware maximum.
| Lead Screw | Steps/mm | Arduino Limit | Max Speed | Firmware Setting |
|---|---|---|---|---|
| 8 TPI (Mach3 CrossFire) | 503.936 | 30,000 steps/sec | 120 IPM | $110=3048 |
| 2 TPI (Gen2 CrossFire) | 125.984 | 30,000 steps/sec | 480 IPM | $110=12192 |
Calculation: Max Speed (mm/sec) = 30,000 steps/sec ÷ steps/mm
With 8 threads per inch lead screws (3.175mm lead):
- 503.936 steps/mm required per millimeter of travel
- At 120 IPM (3,048 mm/min): Uses ~25,400 steps/sec ✓ Safe
- At 200 IPM (5,080 mm/min): Would need ~42,700 steps/sec ❌ Exceeds limit
- At 300 IPM (7,620 mm/min): Would need ~64,000 steps/sec ❌ Far exceeds limit
Result: Commanding speeds above 120 IPM will trigger error messages in FireControl and the machine will move at the hardware maximum (~120 IPM) regardless of commanded speed.
- Plasma cutting speeds: Typically 40-100 IPM depending on material thickness
- Rapid positioning: 120 IPM is plenty fast for moving between cuts
- Gen2 users: With 2 TPI lead screws, you can rapid at 480 IPM due to 4x fewer steps/mm
Note: The firmware max speed settings ($110, $111) are configured appropriately for each lead screw type and prevent you from commanding impossible speeds.
These are baked into the firmware but can be changed at runtime via serial commands ($x=value):
| Setting | Value | Description |
|---|---|---|
$0 |
10 | Step pulse time (microseconds) |
$1 |
255 | Step idle delay (255 = always on) |
$3 |
3 | Direction invert mask (X+Y inverted) |
$100 |
503.936 | X steps/mm (8 TPI = 3.175mm lead) |
$101 |
503.936 | Y steps/mm (8 TPI = 3.175mm lead) |
$102 |
266.666 | Z steps/mm |
$110 |
3048 | X max rate (120 IPM - hardware limited) |
$111 |
3048 | Y max rate (120 IPM - hardware limited) |
$112 |
3810 | Z max rate (150 IPM) |
$120 |
980 | X acceleration (mm/sec^2) |
$121 |
980 | Y acceleration (mm/sec^2) |
$122 |
980 | Z acceleration (mm/sec^2) |
| Setting | Value | Description |
|---|---|---|
$0 |
10 | Step pulse time (microseconds) |
$1 |
255 | Step idle delay (255 = always on) |
$3 |
0 | Direction invert mask (no inversion) |
$100 |
125.984 | X steps/mm (2 TPI = 12.7mm lead) |
$101 |
125.984 | Y steps/mm (2 TPI = 12.7mm lead) |
$102 |
266.666 | Z steps/mm |
$110 |
12192 | X max rate (480 IPM - hardware safe) |
$111 |
12192 | Y max rate (480 IPM - hardware safe) |
$112 |
3810 | Z max rate (150 IPM) |
$120 |
980 | X acceleration (mm/sec^2) |
$121 |
980 | Y acceleration (mm/sec^2) |
$122 |
980 | Z acceleration (mm/sec^2) |
To reset to firmware defaults after flashing: Send $RST=$ in FireControl console, then power cycle the Arduino.
⚠️ WARNING: UNTESTED FUNCTIONALITY The THC (Torch Height Controller) firmware and integration has NOT been tested with actual hardware. This feature is included from the original grbl-ls codebase but remains unverified in this implementation. Use at your own risk and please report results if you test it.
The thc-firmware/ directory contains firmware for a separate Arduino Nano that acts as a Torch Height Controller, replacing the $750 Langmuir LS-THC module with a ~$15 DIY solution.
Arduino Nano clones with CH340 USB chips have VID 1A86 PID 7523, which matches the Langmuir LS-THC — no USB spoofing needed.
See thc-firmware/README.md for full wiring and setup instructions.
| Byte | Command | Description |
|---|---|---|
0xA2 |
DWELL_50 | Pierce delay 50% |
0xA3 |
DWELL_100 | Pierce delay 100% |
0xA4 |
DWELL_150 | Pierce delay 150% |
0xA5 |
DWELL_200 | Pierce delay 200% |
0xA6 |
DWELL_0 | Pierce delay 0% (skip) |
0xA9 |
CANCEL_WAIT | Cancel current dwell immediately |
- Startup banner:
Grbl 1.3ls(FireControl checks this) - Baud rate: 115200
- Status reports:
<Idle|MPos:0.000,0.000,0.000|...|Ov:100,100,100,100>(4 override values — the 4th is the dwell override) - Torch control: M3 = torch on, M5 = torch off (mapped to spindle enable)
- Jogging:
$J=G91 X10 F1000style commands
crossgrbl/
├── grbl/ # GRBL source code (ATmega328P)
│ ├── config.h # Compile-time config (CrossFire defaults)
│ ├── cpu_map.h # Pin assignments
│ ├── defaults.h # Machine defaults (steps/mm, speeds, etc.)
│ └── ... # Core GRBL source files
├── thc-firmware/ # THC controller firmware (Arduino Nano)
├── firmware/ # Pre-built hex files
│ ├── grbl-ls-1.3ls.hex # Ready-to-flash GRBL firmware
│ ├── CrossFire-spoof-16u2.hex # USB spoof for Uno R3 (ATmega16U2)
│ ├── CrossFire-spoof-8u2.hex # USB spoof for Uno R2 (AT90USB82)
│ ├── THC-spoof-8u2.hex # USB spoof for THC (if needed)
│ └── CrossFire-Gen2-v1.3ls-official.hex # Stock Langmuir firmware (reference)
├── docs/images/ # Documentation images
├── Makefile # Build/flash GRBL from source
├── COPYING # GPLv3 License
└── README.md
- Verify USB VID/PID was flashed correctly: check Device Manager for "Langmuir Systems CrossFire"
- If it still shows as "Arduino Uno", the USB firmware flash didn't take — retry DFU mode
- Make sure you're using the correct hex file (16u2 vs 8u2)
- CH340-based Arduino clones cannot be spoofed — you need a genuine Uno or one with an ATmega16U2/AT90USB82
- Check terminal 8 (Enable) is wired to both Leadshine drivers — it must be LOW to enable
- Verify STEP and DIR wires are on the correct terminals (2/5 for X, 3/6 for Y)
- Check your Leadshine driver power supply is on
- Verify the Leadshine drivers are configured for the correct microstepping
- Swap the DIR wire polarity on the Leadshine driver, OR
- Change the direction invert mask:
$3=1(invert X),$3=2(invert Y),$3=3(invert both)
- Check terminal 12 is wired to the CrossFire torch trigger input
- Test manually: send
M3via serial terminal, pin 12 should go HIGH - Verify continuity from terminal 12 to the CrossFire trigger circuit
- Ensure GRBL reports
1.3ls— connect via serial at 115200 baud and check startup banner - If you built from source, verify
GRBL_VERSIONingrbl/grbl.his"1.3ls"
GRBL firmware is licensed under the GNU General Public License v3.0 — see COPYING.
THC firmware is licensed under the MIT License.
- GRBL by Sungeun K. Jeon / Gnea Research LLC
- grbl-ls by Langmuir Systems
- Electronics-Salon for the screw terminal shield