The PiBot CNC Pendant V4.0 is a handheld Bluetooth/RJ12-based controller designed for CNC machines running FluidNC and GRBL-HAL firmware. Developed by PiBot, with firmware support from ESP3D creator Luc, the pendant provides an interface for manually controlling and monitoring CNC routers, laser engravers, and other GRBL/FluidNC-based systems via RJ12 wired or Bluetooth connection.
The device features a capacitive touchscreen, an industrial-grade encoder, a potentiometer knob, a band switch, three independent switches, and a built-in speaker, all housed in an enclosure with a dual-PCB design that allows IO expansion. The pendant operates at 115200 baud over Bluetooth or up to 1,000,000 baud in wired mode, and is powered by a flat-top 18650 battery with onboard charging and power level indication.
PiBot CNC Pendant V4.0 specifications:
- Main Controller – ESP32 (No version specification is mentioned)
- Storage – MicroSD card (one-click upgrade via microSD card coming soon)
- Display – Capacitive touch screen; Most probably 3.5-inch (approx. 76 x 55 mm)
- Audio – Built-in speaker for status feedback
- Connectivity
- Wired – RJ12 port (for V4.7/V4.9 mainboards or IO Expanders)
- Wireless – Independent Bluetooth TX/RX modules (115200 baud support)
- USB – 1x USB Type-C port for firmware updates and charging
- Misc
- 3x Independent physical switches (in the front)
- Industrial-grade encoder (optimized for tactile response)
- Band switch
- Power switch (On/Off)
- Boot and reset button (for firmware flashing)
- Indicator light function button
- Battery level indicator LED
- Potentiometer knob
- Power
- 5V from USB-C
- 18650 flat-top battery (e.g., Sony VTC5/VTC6; not included)
- Charging circuit
- Dimensions – 165 x 60 mm
- Weight – 365g
- Enclosure – 3D-printable casing (STL files provided for DIY repairs/customization)
Warning from the manufacturer: When using the RJ12 wired connection, do not insert the 18650 battery. Doing so can cause a voltage imbalance that may damage the ESP32 chip. The battery is only designed to work with Bluetooth wireless mode.
Note: Since the pendant uses GPIO25 and GPIO27, it cannot be used at the same time as the standard 0.96-inch OLED displays found on most FluidNC controllers (which use those same pins for I2C).
The pendant comes pre-installed with firmware set to 115200 baud, making it “plug-and-play” for most users. It is compatible with FluidDial (CYD button version) and works with FluidNC v3.9.7+ by configuring UART pins (GPIO25 and GPIO27) in the YAML file. A custom PiBot UI co-developed with the ESP3D author is also coming soon with microSD card upgrade support. One thing to note is that while the firmware is open-source, the hardware itself is not fully open-source, except for the STL files for the enclosure.
While searching for more information, I found a post from Lumen Works Engineering mentioning safety and performance issues when using the PiBot CNC Pendant. With its default settings on FluidNC, the encoder wheel can overload the buffer, causing stalled movement or even unintended reverse motion that may lead to a crash. To address this, the creator developed a custom fork of the FluidDial firmware specifically for the PiBot unit, which not only resolves the buffer flooding issue but also enables additional hardware features such as a 4-position band switch (x1, x10, x100, and jog lock) and potentiometer-based dynamic jog speed control. The modified firmware is available on the Fluiddial repo.
As the Pendant supports CNC router controller running FluidNC firmware, it might work with the 6x CNC Controller and TMC2209 Pen/Laser CNC Controller, previously covered on CNX Software. However, it’s probably safer to go with one of the Pibot CNC router controllers for best compatibility.
The PiBot CNC Pendant V4.0 is available on AliExpress for $70.58 and the PiBot Store for $79.99 (discounted from the $99.99). The package includes the main unit, two Bluetooth TX/RX modules, a Bluetooth adapter, an RJ12 module, and a 1-meter communication cable.
Debashis Das is a technical content writer and embedded engineer with over five years of experience in the industry. With expertise in Embedded C, PCB Design, and SEO optimization, he effectively blends difficult technical topics with clear communication
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