[SOLVED] Jetson I2C-CAM communication

Autonomous Machines Jetson & Embedded Systems Jetson TK1
1

Hi everyone,

I’m trying to communicate with an i2c device connected on the i2c bus of my Jetson board. I’m having a hard time trying to find any documentation concerning the i2c interface. The only usefull thing that I’ve found is this topic:
https://devtalk.nvidia.com/default/topic/770603/i2c-port-name-and-i2cbus-number/

So far, I’ve connected my i2c device to the CAM_I2C (3.3V) (i2c-2). When I try to use i2cdetect on bus 2 to find my device:
$ sudo i2cdetect -r 2
The scanning is very long and I get this kernel messages:
[ 553.493850] tegra-i2c tegra12-i2c.2: i2c transfer timed out, addr 0x0003, data 0x00

Is there anything I have to do to be able to communicate with my device through this i2c? Do I have to enable something to start the i2c communication?

Moreover, if i try to scan the other i2c’s (i2c-0 for example) the scanning is done as fast as usual (2-3 seconds) without any kernel message. So I’m wondering if there is something special about this i2c-2 in particular.

Thanks for your help!

2

You might have a hardware issue on your I2C connection.
Using the grinch kernel 19.3.6 and i2ctools I had no trouble programming an EEPROM over HDMI or running detect on the various busses.

3

I tried it with the grinch kernel, same issues. I had a look at the schematics available here:
http://elinux.org/Jetson/I2C
External Image

From what I see, I should have 18V on pin 29 (LDO_1) but I’m measuring 0V. I’m wondering if there is something I forgot to enable. A GPIO or specific register to enable the camera I2C?

BTW, what do you mean by “programming an EEPROM over HDMI” ? How is it related to I2C?

4

OK, problem solved. The LDOs were disabled by default. I’ve been able to activate them using sysfs

echo enabled > /sys/devices/platform/tegra12-i2c.4/i2c-4/4-0040/as3722-regulator.0/regulator/regulator.12/state

Once the LDOs are active I can detect my device using i2cdetect and communicate with it.

5

The HDMI port has a 5V level I2C you can talk to. I2C is part of the HDMI standard.
Thanks for the LDO tip, someone will find that useful.

6

Did you just have to enable that regulator? I have the same problem now, scanning i2c-2 for a device connected to the expansion header.

7

I’m almost positive that this didn’t work for me the first time I tried the 21.3 release, but now it does.

Edit: this does not work for me on 21.3, even after enabling the regulators, but it works reliably on 21.4, so someting must have been fixed.