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The Omega2 has a built-in hardware SPI controller allowing it to communicate with SPI-enabled peripherals. It offers 2 Chip Selects. However, the internal flash storage uses Chip Select 0, so only Chip Select 1 is free for external devices.


The Serial Peripheral Interface (SPI) is a four-wire synchronous communication protocol, largely used to connect microprocessors or microcontrollers to sensors, memory, and other peripherals.

SPI SignalMeaning
SCKSystem Clock
MOSIMaster Out, Slave In – Data sent from the Master to the Slave
MISOMaster In, Slave Out – Data sent from the Slave to the Master
CS/SSChip Select/Slave Select

SPI is a synchronous data bus, meaning that one of the lines is a clock, used to synchronize the bits being sent on the data lines.

The protocol is based on the Master-Worker architecture.

  • The Master will generate the System Clock and the Chip Select signals.
  • Each worker requires its own Chip Select connection to the Master.


The Omega2 has one SPI interface available:

  • The interface supports half-duplex transmissions and can operate in host-mode only.
  • The maximum SPI clock frequency is 40 MHz.
  • The flash storage occupies SPI Chip Select 0 and cannot be used; external devices can be connected to SPI Chip Select 1.
  • External devices connected to the SPI bus can affect the boot sequence under certain conditions. (Refer to special pins - SPI pins for details.)

The Omega2 does not support full-duplex SPI transmissions. This is due to a hardware bug in the underlying MT7688 SoC used in the Omega2.

The SPI and CS1 pins are highlighted on the Omega2/2S diagrams below.

omega2-pinout spi-cs1 pins


The Omega2 SPI interface is available at /dev/spidev0.1.

  • spidev0 is the Omega2's SPI bus number.
  • 1 indicates the device ID, which corresponds to the worker connected to the Omega2's CS1 pin.

Interacting with the SPI bus

The following features are available on the SPI bus.


Onion recommends using the python3-spidev Python module for SPI communication.

The python3-spidev module provides a series of functions that implement SPI communication through the Linux device interface. It also provides an Omega2-specific xfer3 function that implements a half-duplex write-then-read SPI transmission.

For installation and usage instructions see: