These were just some of the reasons he decided to port Grbl to the ESP32 board. Price wise the Arduino and ESP32 are around the same, but the ESP does have the advantage of being much more ...

but the Arduino implementation is preset to a default pinout, so you just need to look it up, and hook up MOSI to MOSI and so on. As of now, it only uses one of the ESP32’s two free SPI units.