Gecko Blaster is a small, inexpensive CNC controller board that is designed to be used with FluidNC firmware https://github.com/bdring/FluidNC . The microcontroller is a an ESP32 in the D1 Mini form factor, like https://www.aliexpress.com/item/1005001621844145.html or https://www.amazon.com/ACEIRMC-ESP-WROOM-32-Bluetooth-Development-Compatible/dp/B08L5X2ZM3
The ESP32 Mini plugs into the Gecko Blaster board, and the board plugs into a "standard" parallel port stepper driver, such as a Gecko G540 https://www.geckodrive.com/g540-4-axis-digital-stepper-drive.html . It should also work with a CNC breakout like https://www.amazon.com/SainSmart-Breakout-Board-Stepper-Driver/dp/B0093Y897A or a 3-axis (or 4-axis) driver board like https://www.amazon.com/Stepper-Controller-Engraving-Milling-Machine/dp/B072J43CHP
Optionally, you can stack an OLED display shield like https://www.amazon.com/Display-Module-SSD1306-ESP8266-Arduino/dp/B07P1QHTTK on top of the ESP32 Mini to get some extra information from the firmware.
The Gecko Blaster board is very simple with only a few components other than connectors, so it is very inexpensive to fabricate. The components are all through-hole for ease of soldering.
The board includes pads for a "Serial Wombat" I2C I/O Expander https://www.amazon.com/Serial-Wombat-Converter-quadrature-Compatible/dp/B08T1QLSV8 attached to a rotary encoder with switch. It was intended for controlling a simple menu system for the OLED display. The code for that has not been written. That part of the hardware has not been tested; in fact the prototype PCB layout had the pads for the Serial Wombat chip too far apart. It would have been possible to spread the pins and tack the chip down but I did not do so.
There are also pads for a pushbutton that connects to a GPIO. It could be used for some random control signal. I do not use it at present.
The board is powered from a USB B connector that has only the power connections, not the data lines. I chose USB B because it is mechanically larger than later USB connectors, and thus likely to be sturdier. The power to the USB B connector comes from an ordinary USB 5V wall cube. There are no components that require significant power, other than the ESP32, so an old-style 500mA USB supply suffices.
The prototype, without the Serial Wombat and rotary switch, is in production use on the CNC router that I use in my golf putter business. The user interface is a 10" Android tablet via the WebUI that is part of FluidNC.
The minimum system would need only three components besides the PCB:
- The Mini ESP32 module (~$5)
- A DB25 connector (~$1)
- An electrolytic capacitor 100uF 25V (~$0.25)
- Some Mini ESP32 modules do not have enough capacitance on the power rails, and the power dips when the WiFi radio turns on, leading to brownout resets. The solution is to add extra capacitors on 5V and 3V3. 47uF is probably enough; I used larger ones just because I had them handy.
- A GeckoDrive G540 puts enough load on Z_DIR / GPIO0 to prevent the ESP32 from booting. The solution is to cut the trace from IO0 to DB25 pin 7 and run a wire from GPIO14 to DB25 pin 7, thus repurposing the SW2 input.
- A Leadshine MX3660 pulls up Y_DIR / GPIO12 and prevents the ESP32 from booting. The solution is to cut the traces from GPIO12 to DB25 pin 5, and from TDO/GPIO15 to DB25 pin 1 and run a wire from GPIO15 to DB25 pin 5, thus changing GPIO15/OUTPUT2 to be Y_DIR.