SPI using spidev

The Rapsberry Pi has a SPI interface on its GPIO header. With the spidev driver the FPGA can be used by using only 4 wires (MOSI, MISO, CLCK, and CS). This driver is designed to work with a variety of boards, as long as they expose the spidev device.

Configuration

The configuration of the FPGA consist of the definition of the pins where MOSI, MISO, CLCK, and CS are connected to. Below is the example used for the HUB75HAT.

"connection": {
    "connection_type": "spi",
        "mosi": "j5:14",
        "miso": "j5:12",
        "clk":  "j5:15",
        "cs_n": "j5:11"
}

HAL

Use the following connection string for spidev:

loadrt litexcnc connections="spidev:\dev\spidev0.0"

This will load spidev interface 0 with chip select 0. The available spidev devices can be listed with the code below.

ls /dev/spidev*.*