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Warning: Cannot query I2C bus speed.

Asked by Mario Frischmann on 30 Aug 2017
Latest activity Commented on by Morteza aliyari on 24 Nov 2017
Hy everybody,
I am usining a Raspberry Pi 3 Model B V1.2 and the Support Package for Raspberry Pi.
With the Matlabcommand
mypi = raspi
I can connect to my Raspberry Pi but at the first time I use this command I alwas get following warning:
Warning: Cannot query I2C bus speed.
If I use the commands
disableI2C(mypi)
enableI2C(mypi,400000)
once and clear the variable mypi and try the comment mypi = raspi again it can query the I2C bus speed (40000)
Can anyone help me so it will work at the first time? I use Matlab 2016b
Thank you very much

  1 Comment

hi,i recommend enable i2c from raspberry pi terminal with: sudo raspi-config and add bus speed to your config.txt on rpi3b. it work for me.

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1 Answer

Answer by Manish Annappa on 7 Sep 2017

In order to get more information on the issue, post the output of the following commands
a) Create connection to Raspberry Pi (for the first time)
>> mypi = raspi
b) List all the available I2C bus available and their speed
>> mypi.AvailableI2CBuses
>> mypi.I2CBusSpeed
c) Scan all the I2C buses available to get its address. '<name>' is obtained from the output of mypi.AvailableI2CBuses.
>> scanI2CBus(mypi,'<name>')
d) Create a connection to all the addresses obtained in the above step for every I2C bus.
>> i2cdac = i2cdev(mypi,'<name>','<address>')
e) Write value to every I2C bus connected in above step
>> write(i2cdac,4092)
Refer to the link below for more information on the commands:
https://www.mathworks.com/help/releases/R2016b/supportpkg/raspberrypiio/ug/use-the-i2c-interface-on-the-raspberry-pi-hardware.html

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