I2C detect DragonBoard410c


#1

i2cdetect is very slow

I want to use i2c-1 on DragonBoard410c( Debian jessie, except using kernel I built with Yocto).
I used sudo i2cdetect -y -r 1, but printing a result of this command is slower than my experience.

For the first few seconds

linaro@linaro-developer:~$ sudo i2cdetect -y -r  1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- 

After few seconds

linaro@linaro-developer:~$ sudo i2cdetect -y -r  1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- 

After few seconds

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --            

In my experience( quick mode i2c), printing a result ended in a moment.

Is this behavior correct?
If it is wrong, it would be greatly appreciated if you could tell me why.


#2

If I’m correct, i2cdetect just sends a read byte requests for each address, if there is a device the request is acked, if there is no device (SDA not pulled), request is nacked. This is a relatively quick procedure. I suspect that something is pulling the SDA line but not responding, leading to timeout.

Do you have something connected to i2c-1 ? if yes, did you take care about the 1.8v signaling ?


#3

@Loic
Thank you for a responce.
I don’t have something connected to i2c-1.

But I’ve connected DeekRobot Pro mini to i2c-1 without taking care about the 1.8v signaling.
( Even then the result was the same.)

Turn Around Time of my i2cdetect is longer than 10 sec.


#4

I’ve also seen very slow scanning on this board but transactions to a
known address perform OK (and this is the normal case) so I didn’t worry
about it too much!


#5

@danielt
Thank you! OK, I don’t worry about it, too!