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