This project contains a python module for interfacing with SPI devices from user space via the spidev linux kernel driver.

This is a modified version of the code originally found here

All code is GPLv2 licensed unless explicitly stated otherwise.

import spidev
spi = spidev.SpiDev()
spi.open(bus, device)
to_send = [0x01, 0x02, 0x03]
spi.xfer(to_send)

import spidev
spi = spidev.SpiDev()
spi.open(bus, device)

# Settings (for example)
spi.max_speed_hz = 5000
spi.mode = 0b01

...

• bits_per_word
• cshigh
• loop - Set the "SPI_LOOP" flag to enable loopback mode
• no_cs - Set the "SPI_NO_CS" flag to disable use of the chip select (although the driver may still own the CS pin)
• lsbfirst
• max_speed_hz
• mode - SPI mode as two bit pattern of clock polarity and phase [CPOL|CPHA], min: 0b00 = 0, max: 0b11 = 3
• threewire - SI/SO signals shared

open(bus, device)

Connects to the specified SPI device, opening /dev/spidev<bus>.<device>

readbytes(n)

Read n bytes from SPI device.

writebytes(list of values)

Writes a list of values to SPI device.

xfer(list of values[, speed_hz, delay_usec, bits_per_word])

Performs an SPI transaction. Chip-select should be released and reactivated between blocks. Delay specifies the delay in usec between blocks.

xfer2(list of values[, speed_hz, delay_usec, bits_per_word])

Performs an SPI transaction. Chip-select should be held active between blocks.

xfer3(list of values[, speed_hz, delay_usec, bits_per_word])

Similar to xfer2 but accepts arbitrary large lists. If list size exceeds buffer size (which is read from /sys/module/spidev/parameters/bufsiz), data will be split into smaller chunks and sent in multiple operations.

close()

Disconnects from the SPI device.