[beagleboard] Re: Cannot SSH to BBB anymore

[yassyass]

Thank you for the input Chris and Dennis,

I have picked up working on the BBB again and tried plugging it into a 
display via the mini HDMI and it seems like the beaglebone does not boot 
into the OS as all I see is a blinking cursor top left of the screen.

I tried booting from an SD card and that seems to work fine but I am unsure 
how to access the eMMC to retrieve files before re-imaging. 

Is there a process making that possible?

Thanks in advance

On Thursday, May 17, 2018 at 12:52:38 PM UTC+12, yassyass wrote:
>
> Hi guys,
>
> Not sure what's happened and not sure where to start troubleshooting. 
>
> My BBB won't respond to SSH requests from Terminal on my mac, this was 
> working perfectly fine just days ago and I am trying to go back and 
> understand what changed. 
>
> I worked mostly using Cloud9 and running scripts with Python and JS so I 
> have quite a bit saved on it that I would like to recover if possible 
> before resorting to re-imaging.
>
> The board seems to turn on fine with all the LEDs turn on sequentially and 
> then they start pulsing as they would when the OS is running.
>
> The board is both connected directly to my Mac and to a LAN via ethernet.
>
>

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[beagleboard] Re: Cannot SSH to BBB anymore

[yassyass]

Thanks for that Chris, an arp -a does not return a beaglebone default IP of 
192.168.6.2 on the LAN. 
I will look into the other device addresses on the network and hopefully 
one of them is the BBB. 

I also just thought of using the HDMI link on the board and connect to a 
display and use keyboard directly off it to see what the matter is.

Will report back with results once I find a mini HDMI cable...

On Thursday, May 17, 2018 at 8:03:27 PM UTC+12, Chris Green wrote:
>
> yassyass > wrote: 
> > Hi guys, 
> > 
> > Not sure what's happened and not sure where to start troubleshooting. 
> > 
> > My BBB won't respond to SSH requests from Terminal on my mac, this was 
> > working perfectly fine just days ago and I am trying to go back and 
> > understand what changed. 
> > 
> > I worked mostly using Cloud9 and running scripts with Python and JS so I 
> > have quite a bit saved on it that I would like to recover if possible 
> > before resorting to re-imaging. 
> > 
> > The board seems to turn on fine with all the LEDs turn on sequentially 
> and 
> > then they start pulsing as they would when the OS is running. 
> > 
> > The board is both connected directly to my Mac and to a LAN via 
> ethernet. 
> > 
> Are you sure you're trying to ssh to the right address? 
>
> Do you have any means of checking your LAN to see what devices there 
> are on your LAN?  If so look at the list of IPs and see if you can see 
> the BBB one or (it might have changed) one that you don't recognise. 
>
> -- 
> Chris Green 
> · 
>
>

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[beagleboard] Cannot SSH to BBB anymore

[yassyass]

Hi guys,

Not sure what's happened and not sure where to start troubleshooting. 

My BBB won't respond to SSH requests from Terminal on my mac, this was 
working perfectly fine just days ago and I am trying to go back and 
understand what changed. 

I worked mostly using Cloud9 and running scripts with Python and JS so I 
have quite a bit saved on it that I would like to recover if possible 
before resorting to re-imaging.

The board seems to turn on fine with all the LEDs turn on sequentially and 
then they start pulsing as they would when the OS is running.

The board is both connected directly to my Mac and to a LAN via ethernet.

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Re: [beagleboard] Re: I2C SCL Voltage level too low?

[yassyass]

Thank you John,

It seems like my scope was loading it quite a bit and is now giving much 
better readings using x10 probes. The signals bellow are set to 400 kHz 
using 1kOhm pull-ups









On Friday, April 6, 2018 at 9:49:48 AM UTC+12, john3909 wrote:
>
> Yeah, I agree there is something else going on here. with a 1K resistor, 
> the signals should not have a slow rising time. The rise time doesn’t look 
> like a capacitor, but I agree, that is about the only explanation that 
> would cause the rise time to slow like this. Maybe the I2C part is faulty. 
> Try plugging in another I2C part to see if the problem persists. 
>
> Regards,
> John
>
>
>
>
>
> On Apr 5, 2018, at 8:02 AM, Graham > 
> wrote:
>
>
>  It looks like you have some extra capacitance on the bus.  There should 
> not be any capacitors bridging the I2C data and clock lines. Some of the 
> third-party universal interface cards have extra capacitance, so take those 
> off.
>
> I have never heard of an I2C part with built in pull-up resistors.
>
> Do to the multi-drop nature of the I2C bus, pull up resistors are almost 
> always external. There are some "weak pull up" resistors you could turn on 
> in the BBB, but are too high in value for most applications.
>
> I suggest you read up on how to select pull up resistors for an I2C bus.  
> Phillips (now NXP) initially developed the bus and has good documentation.
> Google: NXP I2C bus documentation
>
> But the short answer is that for a 3.3V bus, resistors in the range of 
> 1.2K to 3.3K should work fine. The value is not critical. You want to pull 
> 1 to 3 mA through the resistor when the bus is low.
>
> --- Graham
>
> ==
>
>
>
>
>
>
>
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[beagleboard] Re: I2C SCL Voltage level too low?

[yassyass]

With the 1k resistors improvement is evident in terms of voltage level for 
the high signal.




However the rise time still seems to be slow and I2C device is still not 
responding to commands. 






I will try and increase the resistance to 3k3 as advised by John and will 
report back with results.

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Re: [beagleboard] I2C SCL Voltage level too low?

[yassyass]

I only managed to get hold of a couple 1k resistors and wired them up to 
the 3v3 rail and got improvements. I am going to assume the internal 
pullups on the I2C device were not enabled. 

<https://lh3.googleusercontent.com/-YOm4FB9y9bs/WsW0xHyK3WI/JGc/6qkSRO6QV9cXpyBA8tTXxo8eE3ctkIcuwCLcBGAs/s1600/ADS8.BMP>


 

On Thursday, April 5, 2018 at 5:22:35 PM UTC+12, john3909 wrote:
>
> You mean decrease the resistor values. Don’t rely on the internal pull up 
> resistors. 4K7 should be OK, but try 3K3 to see if the signals look better. 
>
> Regards,
> John
>
>
>
>
>
> On Apr 4, 2018, at 10:06 PM, yassyass > 
> wrote:
>
> Thanks Wulf, I will attempt to increase the resistor values and get back 
> with results.
>
>
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Re: [beagleboard] I2C SCL Voltage level too low?

[yassyass]

Thanks Wulf, I will attempt to increase the resistor values and get back 
with results.

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[beagleboard] I2C SCL Voltage level too low?

[yassyass]

Wrote a python script using SMBus to write to a slave I2C device. The slave 
is detectable with i2cdetect which results in the following output

debian@beaglebone:~$ i2cdetect -y -r 2

 0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00:  -- -- -- -- -- -- -- -- -- -- -- -- -- 

10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 

20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 

30: 30 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 

40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 

50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- 

60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 

70: -- -- -- -- -- -- -- --


The slave device would not respond to commands and upon inspecting it with 
a scope the voltage signal is appearing lower than the high threshold and 
has a very high time constant it seems. 


The slave device has its own internal pull-up resistors of two 4.7k 
resistors one on each of the buses to the 3V supply on the BBB.


The frequency of the bus is set to 400kHz on i2c-2. The BBB is being 
powered by USB only. 


The following images are of the SCL bus






Could the issue be that the pull up resistors are too high? Does the BBB 
require more power via an external source?



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[beagleboard] Re: How to wire up and configure an i2c device on Beaglebone

[yassyass]

I would like to ask the same question that klemenz is asking. Does cloud9 
provide a framework to run i2c slaves with js or python?

On Wednesday, March 7, 2012 at 10:44:32 PM UTC+13, klemenz...@gmail.com 
wrote:
>
> Hi Dan,
>
> Is there an i2c support within cloud9ide environment or more precisely 
> within bonescript custom .js?
>
> thanks
>
> Dne sobota, 31. december 2011 22:07:43 UTC+1 je oseba Dan napisala:
>>
>> Stan, 
>> Thanks for the info.  I was able to get i2cdetect to work with a 3.3V 
>> device, and will give the level shifter a shot (when I have one) for 
>> the 5V device. 
>> Poking around further, I'm guessing the /sys/class/i2c-adapter 
>> approach mentioned in my question #4 works only if there is a kernel 
>> module for the device.  For example, there is a kernel-module-bmp085 
>> for the BMP085 barometric sensor. 
>> For everything else, there is the i2cget and i2cset approach that you 
>> recommended. 
>> Thanks, 
>> Dan. 
>> On Dec 30, 9:55 pm, Stan Seibert  wrote: 
>> > On Dec 30, 4:50 pm, Dan  wrote: 
>> > 
>> > > 1. Should the pullup resistors always be connected to 3.3V (as 
>> opposed 
>> > > to some other voltage) on the Beaglebone?  I used 5K resistors - is 
>> > > that close enough? (the SRM says 5.5K). 
>> > 
>> > 5k resistors should be fine (I used 4.7k with my device), and since 
>> > the I/O voltage on the board is 3.3V, you should only connect the pull- 
>> > ups to that.  (Pin 3 or 4 on P9) 
>> > 
>> > > 2. Are pins 19 and 20 connected to i2c2 or i2c3?  The SRM manual says 
>> > > i2c2, but based on the results of i2cdetect and other posts I think 
>> > > it's i2c3.  Is there an i2c2 on the Beaglebone? 
>> > 
>> > The numbering in the OS seems to be different than the numbering in 
>> > the SRM.  Pins 19 and 20 are on i2c2 in the hardware numbering scheme, 
>> > but in Linux, the device name is /dev/i2c-3. 
>> > 
>> > > 3. Should i2cdetect automatically find thei2cdevice at the correct 
>> > > address if everything is hooked up correctly? 
>> > 
>> > That depends on your device and whether it will respond to the read 
>> > probes that i2cdetect uses, but in general, yes. 
>> > 
>> > > 4. Do I always need to enter a command similar to the one in Koen's 
>> > > article: "echo bmp085 0x77 > /sys/class/i2c-adapter/i2c-3/ 
>> > > new_device"?  Is the "bmp085" part just a label that I choose, or 
>> does 
>> > > it need to precisely match some setting in the device? 
>> > 
>> > I just interact with my device using the i2cget and i2cset command 
>> > line tools, following the data sheet for my device to know what data 
>> > addresses on the device to set and get. 
>> > 
>> > > 5.Is a 5V device like theBlinkMsupported by the BeagleboneI2C?  If 
>> > > so, is the process for configuring it any different from the process 
>> > > described in Koen's blog post?  (This is the device I tried to get 
>> > > working, and I'm guessing it's not supported). 
>> > 
>> > I've never tried using a 3.3V master and a 5VI2Cdevice, but I have 
>> > used this level shifter for the other direction with an Arduino (5V 
>> > master and 3.3V device): 
>> > 
>> > http://www.sparkfun.com/products/8745 
>> > 
>> > (The description and comments were kind of confusing for this board. 
>> > I used the TX on channel 1 and 2 for theI2CSDA and SCL.)
>
>

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Re: [beagleboard] Re: i2c bus speed

[yassyass]

I was on the IRC a little while ago and was told to modify the 
am335x-boneblack-uboot.dtb file instead as these newer releases are Uboot 
releases.
Doing so actually solved my issue of not being able to change the i2c 
frequency of i2c-2.

Big shout out to zmatt for the help!



On Friday, March 23, 2018 at 2:37:48 PM UTC+13, yassyass wrote:
>
>
> Heres the boot log:
> https://pastebin.com/fgkRkCRv
>
> It seems to say that the I2C busses are set at 100 kHz because "could not 
> find pctldev for node 
> /ocp/l4_wkup@44c0/scm@21/pinmux@800/pinmux_i2c2_pins"
>
> On Thursday, March 22, 2018 at 2:49:01 AM UTC+13, RobertCNelson wrote:
>>
>> On Wed, Mar 21, 2018 at 12:47 AM,   wrote: 
>> > I am having the same issue with my BBB. Modifying the device tree with 
>> > values that should run the I2C clock to 400 kHz does not seem to change 
>> the 
>> > speed upon rebooting. I validated that the .dtb was modified by 
>> unpacking it 
>> > into a .dts again to check if the value was 400 kHz. 
>> > 
>> > Is this method of modifying the device tree not effective anymore in 
>> the 
>> > latest images of Debian? 
>>
>> Check your serial boot log, are you booting what you expect? 
>>
>> Regards, 
>>
>> -- 
>> Robert Nelson 
>> https://rcn-ee.com/ 
>>
>

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