Bit-Efficient Replicator Tech for X, Y, Z axis motor control (3D printers)
Open Source license: MIT (except for VUnit).
- Dependencies
SHELL
bashrc on macos (one can add more shells, it is needed to setup directory and path). In the project bin directory I link to the macos specific files, so one could have another os and replace the links.
HDL
VHDL (currently) Systemverilog (planned) Every unit will have both a VHDL and verilog variant that need to be kept in sync.
VUnit
It is licensed under Mozilla Public License v2.0. Install: search for vunit getting started on the internet.
- HOWTO
setup.bash
- GOAL
Open source development of the digital circuit desciption in both VHDL and verilog (systemverilog). Every source file has a VHDL and a verilog equivalent for training and educational purposes.
The community is available on locals and started validating the stepper motor control with an A4988 driver IC board and the Digilent Arty S7-50 FPGA board (it has an Arduino shield header).
Both Marlin and Klipper are software based 3D printer control solutions for a wide range of single board computers (SBC) and shields/hats/add-on boards.
Software executes sequentially on a controller. By writing and reading IO registers the stepper motor drivers are controlled via software. But interrupts servicing sensors (thermistors measuring the heat bed temperature) will take time away from the control of the motors.
An FPGA does not have that problem since an FPGA is a digital circuit that is reconfigurable. We can move 5 motors in parallel without interfering with each other. And for monitoring and driving the colling fans, we can implement a sofisticated algorithm that operates in parallel and isn't bound by program memory restrictions. The restriction is in the digital circuitry that is available in the FPGA.
We implement the digital circuit in a Hardware Descrption Language (HDL). It describes hardware, while it has a software syntax. It abstracts the underlying technology (FPGA; asic, vendor, ...). And allows automated verification with self-checking test cases. We can always rerun all verification scenario's and see if all PASSED or not whenever we change the HDL source code.
For validation, I use the Arty S7-50 aforementioned since I have it available. But in principle, the design is portable to any technology that supports the use of a digital circuit design.
The MAIN benefit is the parallel control and monitoring versus software (firmware) approaches. We intend to run at clock frequencies higher than 100 MHz to have high resolution stepper motor control. It is basically a hardware accelerator for 3D printers where we have one X-axis, one Y-axis, two Z-axis and one extruder motor (Reprap, Prusa, MK2S, MK3S). The simplest driver, A4988, is used to validate the circuit on target. But obviously, additional driver IC's could be supported in the future.