Pendants for controlling FluidNC CNC firmware

This is a collection of example "pendant" programs showing how to program a auxiliary microcontroller or other computer to interact with a FluidNC CNC controller. FluidNC uses the GRBL serial line protocol for control and status. Unlike classic GRBL controllers which speak that serial protocol on only one serial port, FluidNC can have multiple "channels" simultaneously speaking the serial protocol. The additional channels can include extra serial ports, TCP/Telnet connections, and TCP/WebSocket connections.

Another serial port (UART) is an excellent way to connect an auxiliary microcontroller (MCU). Every MCU has at least one UART, and most have two or more. A UART needs only two signal lines and in some use cases only one. Most MCU UARTs can operate at least as fast as 115200 baud (10K characters per second) and some can go up to 1Mbaud (100K characters per second) or more. That is typically fast enough for a lot of interesting use cases.

In addition to the main operator's console, traditional CNC machines often included an auxiliary control box that hung from a cable near the machine. Those boxes were called "pendants" because they were hanging or suspended from overhead. Typically pendants could perform a subset of the most common operations like jogging and job start/pause/stop. Thus the word "pendant" has come to mean any small auxilary control for a CNC machine.

A FluidNC Pendant that is implemented on a small MCU can be very inexpensive, since suitable MCUs can cost in the range of $1 to a few dollars. The packaging and user-facing I/O devices (small displays, pushbuttons, etc) are likely to dominate the cost.

In principle, a FluidNC Pendant could do anything that a traditional GCode Sender program can do, limited only by the resources of the MCU on which it is implemented. Typically, a given pendant will only do a targeted subset of the possibilities, because otherwise it would be just another sender requiring a full computer. Some examples of small-pendant use cases include:

• Running "playlists" for art machines
• Jog controllers
• Input expansion
• Extra displays like light towers or OLEDs, to show machine state

This code is a collection of examples to help you develop your own custom pendants. Many of the examples can be compiled for several different MCUs, including various ESP32 variants, AVR Arduinos and some ARM MCUs. We expect that you will start with an example that is similar to your desired gadget and modify/extend it for your needs. We do not provide free consultation for doing that.

One of the basic components that is useful for display pendants is the GrblParser class. GrblParser decodes standard GRBL protocol report messages and calls user-supplied code to display the information therein.

This code is not supported. It is provided as a courtesy to help you get started. If you have ideas for new features, please implement them yourself or contract with someone to do so.