This repository was originally forked from UnfinishedBusiness/XmotionFirmware which is a GRBL-based firmware with support for adding a Torch Height Controller for CNC plasma cutting. The same author has also created the control software NcPilot which is a cross-platform g-code sender compatible with this firmware.
At the moment I don't remember why I had to fork it but for some reason the original firmware didn't work very well for me. The problem was that the THC was moving way too slowly. I have refactored the code a bit and broken out the THC stuff in thc.c. I've made some changes so that the THC uses timer 2 to generate interrupts at a frequency of 10 KHz (approximately, I think GRBL does some stuff that messes up the timing slightly) to generate the step pulses. When the THC step pulse goes high, it busy waits for 10 μs before setting the pin low again. It works well enough for my use case. Do not expect this to work if you need very high pulse frequencies, i.e if your desired feedrate(mm/min) * steps_per_mm is some number much higher than ~120k (what I tested with). If you need more speed, experiment with gear/pulley ratios or optimize ISR(TIMER2_OVF_vect) to reach higher pulse frequencies.
The config files in this repository are made for using an Arduino Nano (although the configs can easily be changed). I used the Minicore bootloader since the whole application wouldn't fit in the flash memory with the standard bootloader. Flashing the bootloader can be done by using the Arduino IDE and a spare Arduino as a programmer. The application itself was built and uploaded to the board using PlatformIO.
My specific pinout config (CPU_MAP_PLASMA_NANO in cpu_map.h) can be found below. I'm running a dual-Y stepper setup, so I will refer to the two as Y1 and Y2.
IMPORTANT
Make sure to go through config.h and understand the implications of DISABLE_LIMIT_PIN_PULL_UP and DISABLE_PROBE_PIN_PULL_UP etc. as these settings will vary depending on what sensors/switches are being used. The NanoCut Control software supports configuring limit pin inversion (i.e the meaning of high/low), but not changing the pull-up configuration.
Note D13 is unused because I encountered issues when trying to use it as the Y2 limit. Unsure if pin is used by something else and there is a conflict.
| Pin | Function |
|---|---|
| D2 | X step |
| D3 | Y1 step |
| D4 | Z step |
| D5 | X dir |
| D6 | Y1 dir |
| D7 | Z dir |
| D8 | Stepper driver enable/disable |
| D9 | X limit |
| D10 | Y1 limit |
| D11 | Z limit |
| D12 | Y2 limit |
| D13 | Unused |
| A0 | Arc voltage (0-5V) |
| A1 | Arc OK |
| A2 | Cycle start |
| A3 | Y2 dir |
| A4 | Y2 step |
| A5 | Probe (touch torch) |
| A6 | Coolant flood (not used) |
| A7 | Torch enable |