Software Introduction

Design, CAM, senders and firmware for PiBot FluidNC, grblHAL and GRBL controllers

Getting a part cut involves four different programs, and beginners usually lose time because they expect one program to do everything. This page shows what each layer does, which tools are worth using in 2026, and the commands and workflow that apply to every PiBot controller.

The Toolchain — What Runs Where

Where each kind of software sits. Steps 1–4 run on your computer; steps 5–6 are the controller and the machine.

The firmware and the sender are two different programs. FluidNC, grblHAL or GRBL runs on the PiBot controller. A sender runs on your computer or browser and streams G-code to it. You always need one of each — and for anything you design yourself, a CAD and a CAM step in front.

Firmware and Software Compatibility

Firmware	FluidNC WebUI	gSender	OpenBuilds CONTROL	Candle	UGS	CNCjs	bCNC	ioSender	LaserGRBL	Rayforge	LightBurn
FluidNC	✓	✓	✓	✓	✓	✓	✓	—	✓	✓	✓
grblHAL	—	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓
GRBL 1.1f / 1.1h	—	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓

The same matrix as a picture. Logos are those of the respective projects and vendors.

Compatibility does not mean every plugin or machine feature is automatic. Sender versions change, and grblHAL can be built with different plugins. Test your exact firmware build and software version before operating a machine.

Which Software Should You Use?

A short route to a sensible first choice. Nothing stops you installing several — they all talk to the same controller.

Senders — Streaming G-code to the Board

gSender connected to a grblHAL controller

gSender connected to a grblHAL machine — every region from the diagram above is here: port and state at the top, DRO and jog wheel on the right, 3D toolpath in the middle, feed and spindle overrides along the bottom. Screenshot: Sienci Labs / gSender project.

Every sender arranges these five things differently, but they all have them. Learn the layout once and any sender becomes readable.

Software	Cost	Runs on	Best for
FluidNC WebUI	Free	Any browser, served by the board	First setup and diagnostics on FluidNC. Console, jogging, file upload, SD access, live status — nothing to install.
gSender	Free GPLv3	Windows, macOS (Intel + Apple Silicon), Linux (Intel + ARM)	Everyday CNC work. Modern UI, 3D toolpath view, probing wizards, macros, calibration tools. USB or Ethernet.
UGS — Universal Gcode Sender	Free	Windows, macOS, Linux, Raspberry Pi (Java)	The long-standing reference sender. Classic is minimal; Platform adds a customisable UI, macros, a G-code editor and SVG/DXF/image import.
Candle	Free	Windows, Linux	The simplest possible sender: load G-code, jog, preview the toolpath, run.
OpenBuilds CONTROL	Free	Windows, macOS, Linux	Beginner-friendly but capable, with built-in probing helpers.
CNCjs	Free	Node.js host — typically a Raspberry Pi — used from any browser	Leaving a Pi at the machine and driving it from a phone or laptop on the network.
bCNC	Free	Windows, macOS, Linux (Python)	Probing and auto-levelling. Scans the surface into a height grid and warps the G-code to follow it — the standard answer for PCB isolation milling and warped stock.
ioSender	Free	Windows only	grblHAL builds. Written by grblHAL's own maintainer, so it exposes features other senders do not.

bCNC showing a PCB isolation job with an auto-levelling height map

bCNC running a PCB isolation job. The coloured, warped surface is a probed height map — bCNC bends the G-code to follow it, which is why it is the usual answer for PCB work and uneven stock. Screenshot: bCNC project.

Laser Software

Software	Cost	Runs on	Notes
LightBurn	Paid 30-day trial	Windows, macOS, Linux	The production standard. Design tools, layers, camera alignment, material test grids, rotary. Lists GRBL, FluidNC and grblHAL among supported controllers. Two tiers (Core / Pro); check the site for current pricing.
Rayforge New	Free open source	Linux, Windows (GTK4 / Libadwaita)	The strongest free LightBurn alternative to appear recently: 2D parametric sketcher, multi-layer jobs, camera alignment, rotary support, material recipes, path optimisation and image tracing in one app.
LaserGRBL	Free	Windows only	Lightweight and fast to learn, particularly strong at raster photo engraving. Sends only — design elsewhere.
Inkscape + laser extension	Free	Windows, macOS, Linux	Design in Inkscape, then export G-code with the J Tech Photonics Laser Tool or a gcode-tools extension, then send with LaserGRBL or a CNC sender. Three steps instead of one — fine occasionally, tiring daily.

Rayforge showing a rotary laser job with a layered workflow

Rayforge previewing a rotary job. The panel on the right is the layer workflow — a Contour pass at 80% power and an Engrave pass at 100%, each with its own settings. MIT-licensed and free. Screenshot: Rayforge project.

LaserGRBL raster workflow from artwork to engraved result

LaserGRBL end to end: source artwork, the raster import and vectorise dialog, the G-code preview, and the finished engraving. Screenshot: LaserGRBL project.

Design and CAM — Making the G-code

A sender does not create toolpaths. For anything you design yourself you need a CAD step and a CAM step first. These are the free and near-free options that produce GRBL-compatible G-code.

Software	Cost	Covers	Notes
Carbide Create	Free	2D CAD + CAM	From the makers of Shapeoko. Easy to learn, runs offline, and its G-code works on most GRBL routers. A good first CAM program.
Easel	Free tier	CAD + CAM + sender	Browser-based, so it runs anywhere — but it is cloud-only, with no offline mode.
Kiri:Moto	Free	CAM	Browser CAM that turns STL models into G-code; also available as an Onshape plugin. CAMLab (Sienci) is built on the same engine.
FreeCAD	Free open source	Parametric 3D CAD + CAM	Fully open source with a Path workbench for G-code. Very capable, but the CAM workflow has a real learning curve.
Inkscape	Free open source	2D vector design	The usual starting point for laser artwork and 2D profiles; add an extension to emit G-code.
Estlcam	~€50–60	CAM + sender	Unusually beginner-friendly for 2.5D routing. The trial keeps working with a nag screen, so you can evaluate it properly.

Not sure where to start? Set the machine up with the FluidNC WebUI — it is already on the controller. Once it homes and jogs correctly, add gSender (router) or LightBurn / LaserGRBL / Rayforge (laser) for real jobs, and Carbide Create or Kiri:Moto to make the G-code.

Machine States — and How to Get Out of Them

Every GRBL-family controller is always in one state, and most beginner confusion is really a state problem: the machine will not move because it is in Alarm, or a job will not resume because it is in Hold.

The states you meet in practice, and the single character or command that moves between them.

$X is not the same as homing. It only clears the alarm so the machine will move — the controller still does not know where it is. Use $X to get out of trouble, then $H to establish real position.

Essential Commands

Type these into the sender's console or the FluidNC WebUI command line. They behave the same on GRBL, grblHAL and FluidNC unless noted.

System commands

Command	What it does
`$$`	View all settings. `$x=val` writes one, e.g. `$110=5000`.
`$#`	View G-code parameters — G54–G59 work offsets, G28/G30 positions, tool length offset, probe result.
`$G`	Report active modal states (motion mode, coordinate system, units, plane…).
`$I`	Show firmware version and build info.
`$N`	Show startup blocks. `$N0=`line stores G-code that runs at every reset.
`$H`	Run the homing cycle. The only correct way to establish machine position.
`$X`	Clear the alarm lock. Movement is allowed again, but position is still unknown.
`$C`	Check mode — parse the G-code and report errors without moving anything.
`$J=`line	Jog without disturbing modal state, e.g. `$J=G91 X10 F1000`.
$RST=$ / `$RST=#` / `$RST=*`	Reset settings / clear work offsets / erase everything. Use with care.
`$SLP`	Sleep mode — de-energises steppers, spindle and coolant until reset.

Real-time commands

These act immediately, even mid-job, and are never queued behind buffered motion.

Key	What it does
`!`	Feed hold — decelerate to a controlled stop without losing position.
`~`	Cycle start / resume — continue after a feed hold or an `M0` pause.
`?`	Status report — current state plus machine and work position.
`Ctrl-X`	Soft reset — stop and reset the firmware without a power cycle.

Senders expose feed, rapid and spindle overrides as buttons rather than typed characters — typically ±10% and ±1% steps over a 10–200% range for feed and spindle, and 100 / 50 / 25% for rapids.

FluidNC additions

Command	What it does
`$CMD`	List every command this firmware supports. The fastest way to explore FluidNC.
`$S`	Show all settings. Most commands also have a long form, e.g. `$Gcode/Mode` for `$G`.
`$Limits`	Live monitor of limit, probe and tool-setter inputs. Send `!` to leave the monitor.
`$MD` / `$ME`	Disable / enable the steppers so an axis can be moved by hand. `$MD=X` targets one axis.
`$MI`	Re-initialise the motors — useful after powering the drivers late or changing a run-current setting.
`$SS`	Repeat the startup messages, for when the console was opened after boot.
`$Bye`	Restart the controller from the console.

FluidNC $ commands generally only work in Idle state. If one is refused, stop the job or clear the alarm first.

Machine Zero vs Work Zero

Two different origins exist at the same time, and mixing them up is the most common way to crash a first job.

Machine zero comes from homing and never changes. Work zero is where your part starts, and you set it for every job.

First Run, Step by Step

Connect. USB serial, or join the controller's Wi-Fi and open the WebUI. Serial senders use 115200 baud.
Check it answers. Send ? — you should get a status line. Send $I to confirm the firmware build.
Clear the alarm. A controller with homing enabled starts in Alarm. Send $X to unlock, or go straight to homing.
Home the machine. Send $H. Watch the first homing move with a hand on the power switch — a reversed direction or a mis-wired switch shows up here.
Check the limit inputs before trusting them. On FluidNC $Limits shows every input live; on PiBot boards the matching bench test is step 2.5 of your controller's checklist.
Set the work zero. Jog to the start point and zero the axes in your sender, then confirm with $#.
Dry-run first. Use $C check mode, or run the job with the spindle/laser off and Z raised, before you cut anything.

The FluidNC Toolset

Beyond the WebUI, the FluidNC project ships several tools that are directly useful on PiBot boards.

FluidNC WebUI

Served by the controller itself over Wi-Fi. Console, jogging, file upload, SD browsing and live status from a browser on any device.

FluidNC Web Installer

Flashes firmware straight from a Chrome-family browser over USB — no toolchain, no Python. The usual way to install or update.

FluidTerm

A serial terminal aimed at FluidNC. Shows the boot log and startup messages that a graphical sender hides — the first place to look when a board seems dead.

FluidDial pendant

A physical jog dial. It can run over ESP-NOW, a direct radio link between ESP32s, so the pendant keeps working even if your Wi-Fi network does not.

FluidTerm running on Windows, showing its shortcut keys

FluidTerm on a PiBot board — it prints its own shortcut keys on connect: Ctrl-U upload, Ctrl-R reset, Ctrl-S STM32 loader, Ctrl-Q exit.

PiBot pendants use ESP3D Wi-Fi, FluidDial over ESP-NOW, or a wired RJ12 connection depending on model — see your controller's 4.4 Connect Pendant page for what applies to your board.

Connection Methods

The ways a PiBot controller can be reached. USB and Wi-Fi are the two you will use for setup.

Main USB

Firmware installation, boot-log diagnosis and desktop senders. 115200 baud. Install the CP2102 / CH340 driver if the port never appears, and avoid charge-only cables.

Wi-Fi

FluidNC WebUI, or a network-enabled grblHAL build. PiBot boards ship with the access point fluidnc, password 12345678, WebUI at 192.168.0.1. You can also join the board to your own router from the WebUI.

SD card

Local G-code storage when enabled by the firmware and the YAML/build. Running from SD removes USB dropouts and sender stalls from the equation entirely — worth it for long jobs.

RJ12 / auxiliary USB

Model-specific pendant and expansion interfaces. They are not automatically general-purpose PC connections — check your controller's pinout page first.

CNCjs runs in a browser and is usually installed on a Raspberry Pi left at the machine. Screenshot: CNCjs project.

Candle — about as simple as a sender gets: load, preview, jog, run. Screenshot: Candle project.

UGS Platform — the long-standing reference sender, Java-based so it also runs on a Raspberry Pi. Screenshot: Universal Gcode Sender project.

Going Further

Probing

A touch plate finds the top of the stock and sets Z zero far more accurately than paper-shimming. gSender and OpenBuilds CONTROL both ship guided probing wizards; PiBot boards expose a dedicated probe input.

Surface auto-levelling

For PCB isolation milling or warped stock, bCNC scans a grid of probe points and warps the G-code so a 0.1 mm engraving follows the real surface instead of an imaginary flat plane.

Macros and startup blocks

$N0= stores a G-code line that runs at every reset — handy for forcing units or a coordinate system. Senders add their own macro buttons for tool changes and repeat operations.

Running from SD

Upload the file through the WebUI, then start it from the controller. The job no longer depends on your computer staying awake, connected and un-updated.

Common Problems

Symptom	Where to look
Serial port missing	USB driver not installed, a charge-only cable, or the port is still held open by another sender.
Connects but replies are garbage	Wrong baud rate — use 115200.
Stuck in `Alarm` after power-on	Normal when homing is enabled. `$X` to unlock, then `$H` to home.
Homes the wrong way, or into the frame	Homing direction or limit-switch pin assignment. Cut power first, then re-check wiring and axis configuration.
Cuts in the wrong place	Work zero, not machine zero. Re-zero on the stock and confirm the G54 offset with `$#`.
Laser fires while jogging, or never fires	Laser mode and the sender's S-value range. On FluidNC the laser is a separate tool from the PWM spindle — select it with `M6`.
Job stutters or stops part-way	USB noise or a busy computer. Run from SD card, and route the data cable away from motor and spindle wiring.
Engraving depth varies across the sheet	The stock or the bed is not flat. Probe and auto-level with bCNC, or face the spoilboard.

Official References

Firmware — FluidNC project · FluidNC documentation · FluidNC Web Installer · grblHAL project · GRBL project · GRBL v1.1 command reference
CNC senders — gSender · Universal Gcode Sender · Candle · OpenBuilds CONTROL · CNCjs · bCNC · ioSender
Laser software — LightBurn · Rayforge · LaserGRBL · LightBurn Scanning Offset Adjustment
Design and CAM — Carbide Create · Easel · Kiri:Moto · FreeCAD · Inkscape · Estlcam

Screenshot credits. Application screenshots on this page belong to their respective projects and vendors (gSender / Sienci Labs, bCNC, Rayforge, LaserGRBL, CNCjs, Candle, Universal Gcode Sender). They are reproduced here to identify and describe each program. Logos are the property of their owners. PiBot is not affiliated with or endorsed by any of them.

For troubleshooting, continue to the shared PiBot Controller FAQ.