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https://github.com/kplindegaard/smbus2
A drop-in replacement for smbus-cffi/smbus-python in pure Python
https://github.com/kplindegaard/smbus2
Last synced: 4 days ago
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A drop-in replacement for smbus-cffi/smbus-python in pure Python
- Host: GitHub
- URL: https://github.com/kplindegaard/smbus2
- Owner: kplindegaard
- License: mit
- Created: 2016-04-03T23:49:03.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2024-04-04T10:28:08.000Z (10 months ago)
- Last Synced: 2024-04-25T12:42:42.061Z (9 months ago)
- Language: Python
- Size: 114 KB
- Stars: 230
- Watchers: 17
- Forks: 66
- Open Issues: 27
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# smbus2
A drop-in replacement for smbus-cffi/smbus-python in pure Python
[](https://github.com/kplindegaard/smbus2/actions/workflows/python-build-test.yml)
[](http://smbus2.readthedocs.io/en/latest/?badge=latest)
[](https://sonarcloud.io/dashboard?id=kplindegaard_smbus2)
[](https://pypi.org/project/smbus2/)
[](https://pypi.org/project/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)
* SMBus Packet Error Checking (PEC) support
* read_byte
* write_byte
* read_byte_data
* write_byte_data
* read_word_data
* write_word_data
* read_i2c_block_data
* write_i2c_block_data
* write_quick
* process_call
* read_block_data
* write_block_data
* block_process_call
* 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.
More information about updates and general changes are recorded in the [change log](https://github.com/kplindegaard/smbus2/blob/master/CHANGELOG.md).
# 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
```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.
```python
from smbus2 import SMBus
with SMBus(1) as bus:
b = bus.read_byte_data(80, 0)
print(b)
```
## Example 1c: Read a byte with PEC enabled
Same example with Packet Error Checking enabled.
```python
from smbus2 import SMBus
with SMBus(1) as bus:
bus.pec = 1 # Enable PEC
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.
```python
from smbus2 import SMBus
with SMBus(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
```python
from smbus2 import SMBus
with SMBus(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.
```python
from smbus2 import SMBus
with SMBus(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
```python
from smbus2 import SMBus, i2c_msg
with SMBus(1) as bus:
# Read 64 bytes from address 80
msg = i2c_msg.read(80, 64)
bus.i2c_rdwr(msg)
# Write a single byte to address 80
msg = i2c_msg.write(80, [65])
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:
```python
from smbus2 import SMBus, i2c_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 SMBus(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.
```python
# 1: Convert message content to list
msg = i2c_msg.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
From [PyPi](https://pypi.org/) with `pip`:
```
pip install smbus2
```
From [conda-forge](https://anaconda.org/conda-forge) using `conda`:
```
conda install -c conda-forge smbus2
```
Installation from source code is straight forward:
```
python setup.py install
```