Read I2C transaction of 2 bytes in Python

Question

I'm trying to implement reading from I2C communication on Python. The problem that I've faced is that the sensor which I'm reading from answers with two bytes in one transaction. Is there a Python library which provides such a reading.

Here is the description of the sensor's answer: Sensor's I2c answer

Sounds more like basic byte arithmetic. Try `val = MSB*2^8+LSB` or similar. — Mika72, Jun 04 '18 at 07:25
I don't have problems with the byte arithmetic, the question is how to gather that two bytes from the sensor. — Георги Няголов, Jun 04 '18 at 07:30
The library of your choice (We don't give library recommendations here.) should have a function to read a "word" which are 16 bits. — Klaus D., Jun 04 '18 at 07:30
You have to configure I2C bus and read the correct address. http://www.instructables.com/id/Raspberry-Pi-I2C-Python/ So supposingly the answer to your question is `smbus` — Mika72, Jun 04 '18 at 07:34
Thank you for the comments, they gave me at least a starting point. Can you give me an example of such a reading or sth. — Георги Няголов, Jun 04 '18 at 07:46

score 1 · Answer 1 · answered Jun 06 '18 at 18:16

1

The library you're looking for is the smbus library. If you're looking to read just two bytes as you suggest, use read_word_data(int addr,char cmd). If you're using some sensor that returns more than 2 bytes, you'll have to use read_block_data(int addr,char cmd) and do some byte arithmetic.

Information on the library: http://www.raspberry-projects.com/pi/programming-in-python/i2c-programming-in-python/using-the-i2c-interface-2

answered Jun 06 '18 at 18:16

samuelnj

1,627
1
10
19

Thank you for the answer. I have already solved the problem with using SMBusWrapper from smbus2 library. The function that I use is read_i2c_block_data(addr, offset, number_of_bytes). – Георги Няголов Jun 08 '18 at 08:58

Read I2C transaction of 2 bytes in Python

1 Answers1