Skip to main content

Python bindings for Linux SPI access through spidev

Project description

Python Spidev
=============

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

All code is MIT licensed unless explicitly stated otherwise.

Usage
-----

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

```python
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

Methods
-------

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.

writebytes2(list of values)

Similar to `writebytes` 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.

Also, `writebytes2` understands [buffer protocol](https://docs.python.org/3/c-api/buffer.html)
so it can accept numpy byte arrays for example without need to convert them with `tolist()` first.
This offers much better performance where you need to transfer frames to SPI-connected displays for instance.

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.

Changelog
---------

3.4
=====

* Changed license to MIT

3.0.1
=====

* Fixed README.md and CHANGELOG.md formatting, hopefully

3.0
===

* Memset fix recommended by Dougie Lawson
* Fixes for Kernel 3.15+ from https://github.com/chrillomat/py-spidev
* Fixes for Python 3/2 compatibility.
* Added subclassing support - https://github.com/doceme/py-spidev/issues/10

2.0
===

Code sourced from http://elk.informatik.fh-augsburg.de/da/da-49/trees/pyap7k/lang/py-spi
and modified.

Pre 2.0
=======

spimodule.c originally uathored by Volker Thoms, 2009.

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for spidev, version 3.4
Filename, size File type Python version Upload date Hashes
Filename, size spidev-3.4.tar.gz (10.2 kB) File type Source Python version None Upload date Hashes View hashes

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN SignalFx SignalFx Supporter DigiCert DigiCert EV certificate StatusPage StatusPage Status page