Name: PiBot STM32 I/O Expander V5
Brand: PiBot
SKU: PISTM050B01
Price: 29.99 USD
Availability: InStock

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PiBot STM32 I/O Expander V5

Stock: In Stock
Brand: PiBot
Weight: 0.11kg
SKU: PISTM050B01

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CURRENT V5 · STM32 UART I/O

Turn one UART into a complete machine I/O hub

Add 18 clearly numbered input and output channels to a compatible PiBot controller through one RJ12 connection—while keeping a downstream RJ12 path available for a PiBot pendant or display. FluidNC is fully documented, and grblHAL is supported through the FNC Expander plugin.

8 optocoupler inputs 10 purpose-built outputs 1,000,000 baud Pendant passthrough Adapter + cable included

Open the complete V5 manual

PiBot STM32 I/O Expander V5 angled product view

8optocoupler inputs · #0–#7

6buffered 5 V logic/PWM · #8–#13

2normally-open PhotoMOS · #14/#15

2External-V MOSFET · #16/#17

What is included

A complete standard package—no communication adapter or cable needs to be added.

Expander V5 main unit × 1

Adapter for PiBot 4.x controller × 1

RJ12 communication cable × 1

The RJ12 selectors above the Description are for optional spare accessories. Every standard V5 package already includes the 4.x adapter and one RJ12 communication cable. The adapter is used with V4.96 Pro and V4.7B; V5.88 Ultra and V5.77 Carrier use the documented direct RJ12 path.

Why choose the V5 expander?

More I/O without replacing the controller

A single UART connection adds switch, sensor, coolant, relay and accessory channels to an existing compatible controller. The numbered channel system keeps YAML assignments easy to read.

Inputs designed for real machines

Eight optocoupler input channels support ordinary contacts and NPN (sinking / open-collector) 3-wire sensors. Select 5 V or VMOT so the input side matches approved 5 V, 12 V or 24 V NPN field devices; PNP sensors are not compatible.

The right output for each job

Choose buffered 5 V logic/PWM, a normally-open solid-state contact, or an External-V low-side MOSFET channel instead of forcing every accessory through one output type.

Keep the pendant connection

The controller-side and pendant-side RJ12 paths each have their own RX/TX swap jumpers, making it easier to correct serial direction without rebuilding a cable.

18 channels, four clearly separated jobs

Every connection is labeled by the same channel number used in FluidNC YAML. You configure the job of the channel; you do not need to work with the STM32 package pin names.

#0–#7 · Optocoupler inputsDry contacts connect Signal to GND. Powered sensors must use an NPN (sinking / open-collector) output; PNP sensors cannot trigger these inputs.

#8–#13 · Buffered 5 V outputsSix digital/PWM-capable logic outputs through 74AHCT125 buffering. Use them as control signals, not as high-current power outputs.

#14/#15 · PhotoMOS outputsTwo onboard normally-open solid-state relay contacts with status LEDs—ideal for a clean first M7/M8 function test.

#16/#17 · External-V MOSFET outputsTwo low-side outputs powered from External V for suitable low-voltage DC loads. Use correctly rated protection for the actual load.

Conservative board-level working limits: keep each PhotoMOS channel at or below 1 A for low-voltage loads (recommended no more than 24 V DC / 12 V AC), and each MOSFET channel at or below 24 V DC / 3 A. Use an external relay, SSR or power driver when the load or inrush exceeds these limits.

PiBot STM32 I/O Expander V5 PinMap and numbered channel callouts

V5 PinMap overview. Read the connector labels and numbered channels before wiring. Open the image for full resolution.

Built for the current PiBot controller family

V5.88 UltraDirect documented RJ12 path

V5.77 CarrierDirect documented RJ12 path

V4.96 ProUses the included PiBot 4.x adapter

V4.7BUses the included PiBot 4.x adapter

Use the exact controller model's Wiki wiring and YAML. V5.88/V5.77 use a different UART GPIO pair from V4.96/V4.7B, so configuration must not be copied blindly between boards.

From the box to a verified output

The Expander V5 ships with the universal FluidNC STM32 Expander firmware already installed. Add the controller-side YAML, connect the documented RJ12 path, then run one short LED test.

Connect the correct controller path.
Direct RJ12 on V5.88/V5.77, or the included 4.x adapter on V4.96/V4.7B.

Apply the matching FluidNC YAML.
Set the documented UART and map the numbered expander channels to machine functions.

Send M7, M8 and M9.
Verify the #14 and #15 onboard output LEDs before connecting the final loads.

Follow the complete installation and test chapter

REPRESENTATIVE OUTPUT TEST

M7#14 LED ON

M8#15 LED ON

M9BOTH OFF

Visible confirmation before the machine load is connected

Expansion without giving up your pendant

Top view of PiBot STM32 I/O Expander V5 with controller and pendant RJ12 ports

Controller → Expander V5 → Pendant

The two RJ12 sockets form an inline serial path. Expander-specific messages are handled by the STM32; the remaining serial traffic continues to the downstream pendant or display.

Independent RX/TX correction
Separate jumper groups are provided for the controller side and pendant side.

Fast serial link
Normal FluidNC operation uses 1,000,000 baud with 8N1 framing.

Change cables and jumpers only when fully powered off.
Remove controller, VMOT, External V and pendant battery power before changing the serial path.

Specifications

Controller interfaceUART over RJ12 · 1,000,000 baud · 8N1

Input bank8 optocoupler inputs · channels #0–#7

Logic output bank6 buffered 5 V digital/PWM outputs · #8–#13

Solid-state contacts2 normally-open PhotoMOS outputs · #14/#15

Power outputs2 External-V low-side MOSFET outputs · #16/#17

Sensor supply selectionSW_VCC: 5 V or VMOT for approved 12 V / 24 V NPN sensors; PNP not compatible

Serial routingMainboard RJ12 + downstream pendant RJ12 · dual swap jumpers

Board and firmware70 × 90 mm · universal FluidNC Expander firmware pre-installed

Size and mounting

Expander V5 70 by 90 millimeter PCB dimensions and mounting hole positions

PCB size: 70 × 90 mm. Open the drawing for full mounting-hole dimensions.

Manual, firmware and engineering files

Complete Expander V5 Manual

Previous V4 / V4.1 Manual

STM32 Expander Firmware

V5 Schematic PDF

PiBot Discord Support

Firmware is already installed before shipment. The firmware package is provided for recovery or future maintenance; normal setup starts with the correct controller wiring and firmware-specific configuration.

Frequently asked questions

Do I need to flash the Expander before first use?

No. The universal FluidNC STM32 Expander firmware is installed before shipment. You still need the matching controller wiring and YAML configuration.

Can I connect a PiBot pendant after the Expander?

Yes. Use the RJ12 socket labeled for the pendant and follow the manual's battery and RX/TX jumper instructions.

Does it work with 12 V or 24 V sensors?

Yes, with approved NPN (sinking / open-collector) sensors. Use VMOT through SW_VCC and set the jumper before power is applied. PNP sensors cannot trigger the inputs; because V5 has no reverse-blocking diode, never let Signal rise above SW_VCC.

Can the six 5 V outputs power accessories directly?

Treat #8–#13 as buffered logic/PWM control signals. Use the PhotoMOS, MOSFET or an external power stage appropriate for the load.

What is the quickest functional test?

Map #14/#15 as coolant outputs, send M7 and M8, then confirm the two onboard relay LEDs. M9 turns both off.

Can grblHAL use this hardware?

Yes. The hardware is supported through the grblHAL FNC Expander plugin; use the matching firmware documentation and controller configuration.

Add the I/O your machine needs—without redesigning the controller

Use the complete PiBot manual for controller-specific wiring, firmware setup, RX/TX jumper positions, input setup, output limits and the M7/M8/M9 verification loop.

Read the V5 manual