PiBot V3.28 Isolated
ATmega328P | GRBL 1.1h | Full Optocoupler Isolation
Isolated for Real MachinesBuilt for CNC Machines
True Isolation
Optocouplers on the control I/O plus a dedicated B0505S isolated power rail.
High-Speed PWM
Toshiba TLP2395 high-speed optocoupler for a cleaner spindle or laser signal.
0-10V Output
Direct analog speed command for compatible VFD spindle systems.
XXYYZ Outputs
Five motor outputs with dual X and dual Y channels for gantry machines.
Full Status LEDs
Visual status indication makes wiring checks and troubleshooting faster.
Two Driver Options
Use onboard step-stick drivers or connect external EN / STEP / DIR drivers.
Industrial Inputs
Selectable switch-voltage input supports common 5V, 12V and 24V wiring.
Reverse Protection
Input reverse-polarity protection helps reduce damage from wiring mistakes.
V3.28 Isolated vs. Arduino CNC Shield
A familiar GRBL workflow, but with the protection and machine connections missing from a basic hobby shield.
| Arduino CNC Shield | PiBot V3.28 Isolated |
|---|---|
| ✕ No electrical isolation | ✓ Optocoupler-isolated control I/O |
| ✕ No 0-10V analog output | ✓ 0-10V VFD speed output |
| ✕ Usually three motor channels | ✓ XXYYZ - five motor outputs |
| ✕ Onboard step-stick drivers only | ✓ Onboard and external driver support |
| ✕ Limited status indication | ✓ LED status for machine signals |
| ✕ 5V hobby-level switch wiring | ✓ Selectable 5V / 12V / 24V switch input |
| ✕ Arduino Uno plus shield stack | ✓ Single integrated board with USB-C |
| ✕ No input reverse protection | ✓ Reverse-polarity protection |
Pinout & Connection Diagram
The connectors, jumpers and machine signals are clearly labeled for installation and troubleshooting.
PiBot V3.28 Isolated - complete connector and jumper reference
Two GRBL 1.1h Firmware Options
GRBL v1.1h Standard
- ✓ Standard GRBL 1.1h behavior
- ✓ Default GRBL pin mapping
- ✓ Spindle direction support
| Spindle PWM | D11 |
| Spindle Direction | D13 |
| Coolant Mist M7 | Disabled by default |
| Coolant Flood M8 | A3 |
PiBot GRBL v1.1h Custom
- ✓ Optimized PiBot pin mapping
- ✓ Separate spindle-enable output
- ✓ Coolant flood and mist support
| Spindle PWM | D11 |
| Spindle Enable | D13 |
| Coolant Mist M7 | A4 |
| Coolant Flood M8 | A3 |
Get Started
- Connect USB-C. Install the CH340 driver when required by Windows.
- Wire the drivers. Use the onboard driver sockets or the external EN / STEP / DIR outputs.
- Open a sender. Candle, UGS, LightBurn, bCNC and other GRBL senders can connect at 115200 baud.
- Configure safely. Set steps/mm, speed, acceleration, direction, limits and spindle settings for your machine.
Specifications
| MCU | ATmega328P @ 16 MHz |
| Firmware | GRBL 1.1h, pre-loaded; standard and PiBot custom versions |
| Motor Outputs | XXYYZ - five outputs; dual X, dual Y and one Z |
| Driver Support | Onboard step-stick drivers plus external EN / STEP / DIR driver outputs |
| Isolation | Optocoupler-isolated machine I/O with a dedicated B0505S isolated power rail |
| PWM Isolation | Toshiba TLP2395 high-speed optocoupler |
| Spindle Control | PWM, enable/direction and 0-10V analog speed output |
| Coolant | Flood M8 and Mist M7 with the PiBot custom firmware |
| Switch Inputs | Selectable SW-VCC for common 5V, 12V and 24V switch systems |
| Machine Inputs | X / Y / Z limits, probe, abort, hold, resume and reset |
| Status Indicators | LED indication for major machine signals |
| Protection | Input reverse-polarity protection |
| USB | USB-C with CH340C interface |
| PCB | 2-layer PCB with 2 oz copper |
PiBot Automation Control - CNC controller hardware since 2013
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