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Enabling SPI on Raspberry Pi

In most of the cases, it is easy and straight forward to enable SPI for your Raspberry Pi. The basic case can be found here.

This page will explain how to setup any SPI. Please refer to the Raspberry Pi documentation to understand the different SPI available. You should be aware as well that for Raspberry Pi4, some of the configurations are different than for the other version especially for SPI3, 4 and 5.

Basic Hardware SPI usage

The most simple code you can build to use SPI is the following:

using System;
using System.Device.Spi;

namespace TestTest
{
    class Program
    {
        static void Main(string[] args)
        {
            SpiDevice spi = SpiDevice.Create(new SpiConnectionSettings(0));
            spi.WriteByte(0x42);
            var incoming = spi.ReadByte();
        }
    }
}

This will open SPI0, with the default Chip Select. It will then write a byte to the MOSI pin and read 1 byte from the MISO pin.

If you get something like this, it means you need to check the next sections to activate your SPI0:

Unhandled exception. System.IO.IOException: Error 2. Can not open SPI device file '/dev/spidev0.0'.
   at System.Device.Spi.UnixSpiDevice.Initialize()
   at System.Device.Spi.UnixSpiDevice.WriteByte(Byte value)
   at SpiTest.Program.Main(String[] args) in C:\tmp\TestTest\SpiTest\Program.cs:line 11
Aborted

Enabling SPI0 without Hardware Chip Select

In very short, this is the line you'll need to add into the /boot/firmware/config.txt file:

sudo nano /boot/firmware/config.txt

Note

Prior to Bookworm, Raspberry Pi OS stored the boot partition at /boot/. Since Bookworm, the boot partition is located at /boot/firmware/. Adjust the previous line to be sudo nano /boot/firmware/config.txt if you have an older OS version.

Add the line:

dtparam=spi=on

Save the file with ctrl + x then Y then enter

Then reboot:

sudo reboot

This will enable SPI0 where those are the pins which will be selected, only Software Chip Select is activated with the default pins:

SPI Function Header Pin GPIO # Pin Name
MOSI 19 GPIO10 SPI0_MOSI
MISO 21 GPIO09 SPI0_MISO
SCLK 23 GPIO11 SPI0_SCLK
CE0 24 GPIO08 SPI0_CE0_N
CE1 26 GPIO07 SPI0_CE1_N

Enabling any SPI with any Chip Select

In order to activate Chip Select, you'll need to add a specific dtoverlay on the /boot/firmware/config.txt file. If you've used the previous way of activating SPI0, you should comment the line dtparam=spi=on and add what follows using the dtoverlayconfigurations.

Note

Prior to Bookworm, Raspberry Pi OS stored the boot partition at /boot/. Since Bookworm, the boot partition is located at /boot/firmware/. Adjust the previous line to be sudo nano /boot/firmware/config.txt if you have an older OS version.

Here is the table with the different options for SP0 and SP1 (please refer to the Raspberry Pi documentation to activate other SPI)

SPI0

The following dtoverlay definition can be found here.

SPI # Chip Select # Header Pin Default GPIO Pin Name
SPI0 CE0 24 GPIO08 SPI0_CE0_N
SPI0 CE1 26 GPIO07 SPI0_CE1_N

If you want to change the default pins for Chip Select 0 to the GPIO pin 27 (hardware 13), and let's say GPIO pin 22 (hardware 15) for Chip Select 1, just add this line:

dtoverlay=spi0-2cs,cs0_pin=27,cs1_pin=22

In case you only need one, for example GPIO27 (hardware 13) and you don't need the MISO pin which will free the GPIO09 for another usage:

dtoverlay=spi0-1cs,cs0_pin=27,no_miso

There is only for SPI0 that you can use, in both cases with 1 or 2 Chip Select pin the no_misooption.

Important note: Those overlays are only supported in the very last Raspberry Pi OS. You will get the System.IO.IOException: Error 2. Can not open SPI device file '/dev/spidev0.0' error message if you are using them on an older version. You can use spi0-cs where in the previous examples you had spi0-2cs or spi0-1cs.

As an alternative, you can as well use the following command line: sudo raspi-config nonint do_spi 0

So the first example will now give:

dtoverlay=spi0-cs,cs0_pin=27,cs1_pin=22

In older version, no_miso is not supported neither. And you will always get 2 chip select activated and you don't have a way to only select one.

SPI1 to SPI6

The following dtoverlay definition can be found here.

You can use the same behavior as for SPI0 but you can get from 1 to 3 Chip Select and you can also prevent the creation of a specific node /dev/spidev1.0 (here on SPI1) with a specific flag cs0_spidev=disabled (here for Chip Select 0). So to continue the example, if we want this behavior, the dtoverlay would be for the default GPIO pin 18:

dtoverlay=spi1-1cs,cs0_spidev=disabled

Here is another example where we will use SPI4 with 2 Chip Select, CS0 to GPIO pin 4 (default) and we will be ok to have the creation of a /dev/spidev4.0 node and the CS1 to GPIO 17 and we're not ok to have the node /dev/spidev4.1created:

dtoverlay=spi4-2cs,cs1_pin=17,cs1_spidev=disabled

Adding your user to the right permission group

If you're running, or just upgraded to a version published after August 2020, this should be already done. But in case, you can always check that there are the right permissions on SPI:

sudo nano /etc/udev/rules.d/99-com.rules

You should find a line like this one:

SUBSYSTEM=="spidev", GROUP="spi", MODE="0660"

If you don't have it or if you want to adjust the permissions, this is what you'll need to add/adjust, as always save through ctrl + x then Y then enter and then reboot.