• Avoid using SD cards with excessively large capacity or high speed, as the ESP32 library may not support them. We conducted tests using a Class 4 TF card.

• https://wiki.pibot.com/doku.php?id=pibot_cnc_laser_series:v496_pro:docs:xyyzab

• Of course, a 24V probe can be used. Please refer to the pin map. You can set the probe to a port that includes SWVCC (position 2 in the diagram as the input) and select SWVCC at 24V as your working voltage (position 7).
• https://wiki.pibot.com/doku.php?id=pibot_cnc_laser_series:v496_pro:v49pro_diagram_overview:start

• the new version of the expander 4.1 . I added two voltage-dividing resistors. Please check if the silkscreen on the back is marked as 4.1 (the front silkscreen is incorrect).

If you want to use these ports as regular switches, please connect +5V and the signal. Due to the presence of a voltage divider, there will be a 3V voltage at the STM32 port. You can configure it for high-level triggering.

• https://www.youtube.com/watch?v=oF6c_Z9NqZs

• You can use a closed-loop driver, but it can only receive EN, DIR, CLK, and GND signals, with no feedback information sent back to the mainboard. The mainboard only has outputs and lacks input capabilities.

—

• PiBot V4.96 (Controller)
• Pendant V4 (Handheld Controller)
• PiBot STM32 I/O Expander
• Airedale - FluidNC I/O Expander
• FluidNC 6x CNC Controller

While GPIO25 and GPIO27 are virtual serial ports that can be software-configured as RX or TX in the YAML file, the physical RJ12 interface design differs between the PiBot V4.96 and the FluidNC 6x Controller. Specifically, the hardware traces for 25 and 27 are swapped between these two boards.

txd_pin: gpio.27
rxd_pin: gpio.25

txd_pin: gpio.25
rxd_pin: gpio.27

Note: If communication fails in a direct connection, it can be resolved entirely through YAML software adjustments.

The STM32 chip has fixed physical pins for TX1/RX1 (upstream) and TX2/RX2 (downstream). These cannot be changed in the STM32 firmware and must match the physical wiring.

txd_pin: gpio.25
rxd_pin: gpio.27

• Result: The downstream RJ12 signal from the STM32 is natively compatible with Pendant V4.

txd_pin: gpio.27
rxd_pin: gpio.25

• Result: Compatible with Pendant V4 via the expander.

The Airedale expander introduces a hardware conflict when used with the Pendant V4.

Even though virtual swapping is possible in software, the physical signals must follow the STM32 chip's RX/TX architecture. Because the physical ports (25/27) on the PiBot 4.96 and 6X controllers are inverted relative to one another, the resulting signals (TX1/RX1) passing through the Airedale expander to the Pendant's RJ12 port become swapped.

Critical Requirement:
When connecting any controller to the Airedale - FluidNC I/O Expander and then to the Pendant V4, you must physically swap the TXD0 and RXD1 pins on the Pendant V4 hardware. This is because the ESP32's pins on the Pendant must align physically with the STM32's fixed outputs.

Key Takeaway: The Pendant V4 requires a physical RX/TX swap specifically when interfaced through the Airedale - FluidNC I/O Expander due to the fixed hardware UART architecture of the STM32 chip and the specific RJ12 pinout of that board.

— the above Summary only for the fluidial firmware of pendantV4

if your use the ESP3D UI Firmware for Pendant V4， you don't need to swap the cable in physical