BeagleBone Blue cannot detect i2c devices

594 views
Skip to first unread message

William Vining

unread,
Jun 9, 2018, 11:58:19 PM6/9/18
to BeagleBoard
Hello,

I am trying to connect i2c devices to my beablebone blue, but they are not detected. I have tried four different devices, but none of them appear in the output from `i2cdetect -y -r 1' Does anybody have any advice for things I can check to get this working?

Does the i2c connection on the board include pull-up resistors for sda/scl?

Thanks,
Will

honggang wang

unread,
Jun 10, 2018, 4:07:16 PM6/10/18
to BeagleBoard
Hi, 

I have the same problem. hope somebody can help us out.

Best.

Honggang Wang.

在 2018年6月9日星期六 UTC-4下午11:58:19,William Vining写道:

Graham

unread,
Jun 10, 2018, 9:06:34 PM6/10/18
to BeagleBoard
I don't have a BeagleBone Blue, but I would assume that the necessary pull up resistors for the I2C bus to function are NOT included on the Beaglebone board.
You need to supply them externally.

--- Graham

==

William Vining

unread,
Jun 12, 2018, 11:43:01 AM6/12/18
to beagl...@googlegroups.com
Okay, thanks for that info. I have tried with and without pull-ups, but no luck, so I don't think that is the problem.

Will

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to a topic in the Google Groups "BeagleBoard" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/beagleboard/ZsuocPBodP4/unsubscribe.
To unsubscribe from this group and all its topics, send an email to beagleboard...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/e613cbb4-cf7b-44c0-9539-c549f838660e%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Graham

unread,
Jun 12, 2018, 3:18:24 PM6/12/18
to BeagleBoard
Did you try
i2cdetect -y -r 2

Is the I2C device powered by 3.3 Volts?

--- Graham

==

William Vining

unread,
Jun 13, 2018, 9:35:23 AM6/13/18
to BeagleBoard
Graham,

The I2C device is powered by 3.3V, and I have verified that power is going to it (there is a 3.3V out pin sou you can chain devices together and that shows 3.3V when I measure it with a multi-meter).

i2cdetect -y -r 2 and 0 both show devices, but they are not the ones I am looking for (and are present when my external devices are disconnected).

Will

Graham

unread,
Jun 13, 2018, 10:47:46 AM6/13/18
to BeagleBoard
I looked at the BB Blue Schematic, and there are 4.7K pull up resistors on the I2C-1 bus, which is the one pinned out to the external I2C connector.

So, your possibilities are that your part is wired wrong, the part is bad, or the device tree you are using is not set up right for I2C-1.

What do you see when you put an oscilloscope on SDA and SCL lines?

You can usually tell the difference between them with a scope, since SCL has consistent bursts of eight transistions, and the SDA is more random.

Do you have a known good I2C device of any kind that you can hook to the I2C-1 bus for testing.

--- Graham

==

Johan Lind

unread,
Jun 27, 2018, 3:11:04 AM6/27/18
to BeagleBoard
Have you enabled channel 1? By default only channel 0 and 2 are enabled.

Adding the line
uboot_overlay_addr4=/lib/firmware/BB-I2C1-00A0.dtbo
in /boot/uEnv.txt should do it (if you use a recent Debian that is).
 

honggang wang

unread,
Jun 27, 2018, 10:49:46 AM6/27/18
to beagl...@googlegroups.com
Thank you Johan, you are right. After enabling channel 1, i2cdetect can now find my defice.

Best.

Honggang Wang.

 

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups "BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/1bd8cd14-0e6b-4c46-813e-bc6eddb552a0%40googlegroups.com.

William Vining

unread,
Jun 29, 2018, 12:34:33 PM6/29/18
to beagl...@googlegroups.com
This doesn't seem to have worked for me, did you do anything else to get it working, Honggang?

Thanks,
Will

On Wed, Jun 27, 2018, 08:49 honggang wang <honggang...@gmail.com> wrote:
Thank you Johan, you are right. After enabling channel 1, i2cdetect can now find my defice.

Best.

Honggang Wang.
On Wed, Jun 27, 2018 at 3:11 AM, Johan Lind <johan...@orica.com> wrote:
Have you enabled channel 1? By default only channel 0 and 2 are enabled.

Adding the line
uboot_overlay_addr4=/lib/firmware/BB-I2C1-00A0.dtbo
in /boot/uEnv.txt should do it (if you use a recent Debian that is).
 

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups "BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard...@googlegroups.com.

--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to a topic in the Google Groups "BeagleBoard" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/beagleboard/ZsuocPBodP4/unsubscribe.
To unsubscribe from this group and all its topics, send an email to beagleboard...@googlegroups.com.

Robert Nelson

unread,
Jun 29, 2018, 12:42:40 PM6/29/18
to Beagle Board
On Fri, Jun 29, 2018 at 11:34 AM, William Vining <wfvi...@gmail.com> wrote:
> This doesn't seem to have worked for me, did you do anything else to get it
> working, Honggang?

What does this script show:

sudo /opt/scripts/tools/version.sh

Regards,

--
Robert Nelson
https://rcn-ee.com/

William Vining

unread,
Jun 29, 2018, 12:45:16 PM6/29/18
to beagl...@googlegroups.com
Hi, I made a really stupid mistake. After taking a step back to go through everything from the beginning I discovered I had connected my I2C devices to the CAN port and not the I2C port *facepalm*. With the device connected properly, I do not need the line in uEnv.txt to enable the bus, it appears to be enabled by default in the image I downloaded from the beablebone website a few weeks ago.

Thanks for everyone's thoughtful help, 
Will
Reply all
Reply to author
Forward
0 new messages