Metadata-Version: 1.1
Name: smbus2
Version: 0.2.0
Summary: smbus2 is a drop-in replacement for smbus-cffi/smbus-python in pure Python
Home-page: https://github.com/kplindegaard/smbus2
Author: Karl-Petter Lindegaard
Author-email: kp.lindegaard@gmail.com
License: MIT
Description: smbus2
======
A drop-in replacement for smbus-cffi/smbus-python in pure Python
|travis|
.. |travis| image:: https://travis-ci.org/kplindegaard/smbus2.svg?branch=master
:target: https://travis-ci.org/kplindegaard/smbus2
Introduction
============
smbus2 is (yet another) pure Python implementation of the `python-smbus <http://www.lm-sensors.org/browser/i2c-tools/trunk/py-smbus/>`_ package.
It was designed from the ground up with two goals in mind:
1. It should be a drop-in replacement of smbus. The syntax shall be the same.
2. Use the inherent i2c structs and unions to a greater extent than other pure Python implementations like `pysmbus <https://github.com/bjornt/pysmbus>`_ does. By doing so, it will be more feature complete and easier to extend.
Currently supported features are:
* Get i2c capabilities (I2C_FUNCS)
* read_byte
* write_byte
* read_byte_data
* write_byte_data
* read_word_data
* write_word_data
* read_i2c_block_data
* write_i2c_block_data
* i2c_rdwr - *combined write/read transactions with repeated start*
It is developed on Python 2.7 but works without any modifications in Python 3.X too.
SMBus code examples
===================
smbus2 installs next to smbus as the package, so it's not really a 100% replacement. You must change the module name.
Example 1a: Read a byte
-----------------------
.. code:: python
from smbus2 import SMBus
# Open i2c bus 1 and read one byte from address 80, offset 0
bus = SMBus(1)
b = bus.read_byte_data(80, 0)
print(b)
bus.close()
Example 1b: Read a byte using 'with'
------------------------------------
This is the very same example but safer to use since the smbus will be closed automatically when exiting the with block.
.. code:: python
from smbus2 import SMBusWrapper
with SMBusWrapper(1) as bus:
b = bus.read_byte_data(80, 0)
print(b)
Example 2: Read a block of data
-------------------------------
You can read up to 32 bytes at once.
.. code:: python
from smbus2 import SMBusWrapper
with SMBusWrapper(1) as bus:
# Read a block of 16 bytes from address 80, offset 0
block = bus.read_i2c_block_data(80, 0, 16)
# Returned value is a list of 16 bytes
print(block)
Example 3: Write a byte
-----------------------
.. code:: python
from smbus2 import SMBusWrapper
with SMBusWrapper(1) as bus:
# Write a byte to address 80, offset 0
data = 45
bus.write_byte_data(80, 0, data)
Example 4: Write a block of data
--------------------------------
It is possible to write 32 bytes at the time, but I have found that error-prone. Write less and add a delay in between if you run into trouble.
.. code:: python
from smbus2 import SMBusWrapper
with SMBusWrapper(1) as bus:
# Write a block of 8 bytes to address 80 from offset 0
data = [1, 2, 3, 4, 5, 6, 7, 8]
bus.write_i2c_block_data(80, 0, data)
I2C
===
Starting with v0.2, the smbus2 library also has support for combined read and write transactions. *i2c_rdwr* is not really a SMBus feature but comes in handy when the master needs to:
1. read or write bulks of data larger than SMBus' 32 bytes limit.
1. write some data and then read from the slave with a repeated start and no stop bit between.
Each operation is represented by a *i2c_msg* message object.
Example 5: Single i2c_rdwr
--------------------------
.. code:: python
from smbus2 import SMBus, ic_msg
with SMBusWrapper(1) as bus:
# Read 64 bytes from address 80
msg = i2c_msg.read(80, 64)
bus.i2c_rdwr(msg)
# Write some bytes to address 80
msg = i2c_msg.write(80, [65, 66, 67, 68])
bus.i2c_rdwr(msg)
Example 6: Dual i2c_rdwr
------------------------
To perform dual operations just add more i2c_msg instances to the bus call:
.. code:: python
from smbus2 import SMBus, ic_msg
# Single transaction writing two bytes then read two at address 80
write = i2c_msg.write(80, [40, 50])
read = i2c_msg.read(80, 2)
with SMBusWrapper(1) as bus:
bus.i2c_rdwr(write, read)
Example 7: Access i2c_msg data
------------------------------
All data is contained in the i2c_msg instances. Here are some data access alternatives.
.. code:: python
# 1: Convert message content to list
msg = i2c.write(60, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
data = list(msg) # data = [1, 2, 3, ...]
print(len(data)) # => 10
# 2: i2c_msg is iterable
for value in msg:
print(value)
# 3: Through i2c_msg properties
for k in range(msg.len):
print(msg.buf[k])
Installation instructions
=========================
smbus2 is pure Python code and requires no compilation. Installation is easy:
.. code:: bash
python setup.py install
Or just use pip
.. code:: bash
pip install smbus2
Keywords: smbus,smbus2,python,i2c,raspberrypi,linux
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Topic :: Utilities
Classifier: License :: OSI Approved :: MIT License
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3