Warning: Cannot query I2C bus speed.

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

[Morteza aliyari]

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.

Answer 1

[Manish Annappa]

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