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 Optocouplers on all I/O + B0505S isolated 5V

⚡ 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

VS

V3.28 Isolated

✖ No isolation

I/O

✔ Optocoupler-isolated inputs & outputs

✖ 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 CH340C

✖ Need Arduino IDE to flash

FW

✔ Pre-loaded + WebSerial tool

✖ No optocoupler at all

PWM

✔ Toshiba TLP2395 high-speed opto

🔌 Pinout & Connection Diagram

Every connector, jumper and indicator on the V3.28 Isolated — fully labeled. Keep this open as your wiring reference while you set up.

PiBot V3.28 Isolated — complete connector & jumper map

1Limits & Probe — X / Y / Z limit + Probe inputs (GND, SW-VCC)

2Button Inputs — Abort, Hold, Resume, Reset

3Isolated Outputs — Coolmist (A4), Coolant (A3), Dir-En (D13)

4Isolated PWM — ISO-PWM (D11) + GND-ISO

50–10V Output — PWM-synced analog + GND

6Main Power — VIN 12–24V + GND

7Vmot-Driver — onboard driver motor supply

8Driver Jumpers — MS1 / MS2 / MS3 microstep config

9External Driver — EN/STP/DIR/GND ×5 (X1,X2,Y1,Y2,Z)

10Motor Outputs — onboard driver to motors ×5

11USB-C — PC connection (CH340C)

12RST Button — board reset

13SW-VCC — limit-switch input voltage: 5V (default) or Vmot-Main

14ICSP — MISO / MOSI / SCK / RST programming header

15IO Header — A4 / A6 / A7 with 5V / GND

📥 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	Optocouplers on all I/O. Outputs add a dedicated B0505S DC-DC isolated 5V rail (GND-ISO); input optos field-powered via SW-VCC
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	SW-VCC selectable 5V / Vmot-Main (limit-switch input voltage); 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-C via CH340C
PCB	2-layer, 2 oz copper

📥 WebSerial Firmware Tool 🛒 PiBot Store

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