PiBot V3.28 Isolated

ATmega328P · GRBL 1.1h · Full Optocoupler Isolation

Isolated for Real Machines

XXYYZ5 Outputs

GRBL 1.1hFirmware

100%Isolated I/O

0–10VSpindle Output

🛡️ True Isolation B0505S DC-DC isolated power + optocouplers

⚡ High-Speed PWM Toshiba TLP2395 optocoupler

📈 0–10V Output Direct VFD speed control

🔁 XXYYZ Dual X & Y each 2 outputs

🟢 Full LED Status Every I/O pin has LED indicator

⚙️ Onboard + External Both driver types supported

🔋 24V / 12V Input Industrial switch compatible

🚫 Reverse Protection Anti-reverse polarity design

📊 V3.28 Isolated vs. Arduino CNC Shield

The Arduino CNC Shield is common — but it has zero isolation, no 0–10V, and no reverse protection.

Arduino CNC Shield

V3.28 Isolated

✖ No isolation

I/O

✔ B0505S DC-DC + optocoupler

✖ No analog output

0–10V

✔ 0–10V spindle speed output

✖ No reverse protection

SAFE

✔ Anti-reverse polarity design

✖ No LED indicators

LED

✔ Every I/O pin has LED

✖ Onboard A4988 only

DRV

✔ Onboard + external drivers

✖ 3 axes, no dual output

AXES

✔ XXYYZ — dual X & Y

✖ 5V only inputs

INPUT

✔ 24V / 12V industrial switches

✖ Stacks on Uno — wobbly

BUILD

✔ Single board with CH340

✖ Need Arduino IDE to flash

✔ Pre-loaded + WebSerial tool

✖ No optocoupler at all

PWM

✔ Toshiba TLP2395 high-speed opto

📥 Two Firmware Options

Flash either version from your browser — PiBot WebSerial Tool — plug USB, click flash, done.

OFFICIAL

📄 GRBL v1.1h Standard

Standard GRBL 1.1h features
Default pin mapping
Supports Spindle Direction

Default Pin Mapping
Spindle PWM	D11
Spindle Direction	D13
Coolant Mist (M7)	Disabled by default
Coolant Flood (M8)	A3

CUSTOM

⭐ GRBL v1.1h Custom

Customized from GRBL 1.1h
Optimized pin mapping
Supports Spindle Enable and Coolant Mist

Custom Pin Mapping
Spindle PWM	D11	(unchanged)
Spindle Enable	D13	← M3/M4 OPEN
Coolant Mist (M7)	A4	← M7 OPEN
Coolant Flood (M8)	A3	(unchanged)

⚠ Note: Custom firmware is optimized for V3.28 Isolated hardware. To build it yourself, edit config.h.
All outputs active-high. Active-low inputs: X/Y/Z limits, probe, abort, resume, hold. Short signal to GND with a jumper to test.
CH340 Driver: If serial port not listed, install CH340/CH341 driver first.

🚀 Get Started

Plug in USB. Connect V3.28 to PC. Install CH340 driver if needed (Windows).

Wire drivers. Use onboard driver sockets or connect external drivers (TB6600, DM542, etc.) via Step/Dir/Enable.

Open sender. Candle, UGS, LightBurn, bCNC — any GRBL sender. Baud: 115200.

Configure. Type $$ to view settings. Set steps/mm, speed, acceleration for your machine.

📋 Specifications

MCU	ATmega328P @ 16 MHz
Firmware	GRBL 1.1h (pre-loaded, 2 versions)
Motor Outputs	XXYYZ — 5 outputs (X & Y dual, Z single)
Driver Support	Onboard sockets + external driver output (5V Step/Dir/Enable)
Isolation	B0505S DC-DC isolated 5V + optocouplers on all I/O
PWM Isolation	Toshiba TLP2395 (TPL,ES) high-speed optocoupler
Spindle	PWM + Enable/Direction + 0–10V analog output
Coolant	Flood (M8) + Mist (M7, custom FW)
Switch Input	24V / 12V industrial switch compatible
Inputs	X/Y/Z limits, Probe, Abort, Resume, Hold (active-low)
LED Indicators	Every I/O pin has LED status indicator
Protection	Reverse polarity protection
USB	USB-B via CH340
PCB	2-layer, 2 oz copper, RoHS

📥 WebSerial Firmware Tool 🛒 PiBot Store

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