Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

SPI1 shows the same 1.8v output.  I will attempt to move to another BBB (a 
BBG actually) and if things work there then I'll assume I toasted the SPI 
on this board.

On Tuesday, March 22, 2016 at 1:07:43 PM UTC-4, Walker Archer wrote:
>
> I suspect you're exactly right Wulf Man.  I was not really paying 
> attention to the order I applied the power and I was assuming that the POT 
> voltage would be isolated from the digital control side of the chip.  But I 
> also assumed that if I blew the drivers that I would no longer get any 
> signal from that pin.  Is it normal to get a reduced voltage?  I suppose I 
> could almost fix the issue with an opamp (except I'd be worried that the 
> defective pin would completely go dark someday.)
>
> If I really did blow those pins then I'll get a good signal out of SPI1 
> when I test it tonight.  How would I prevent this in the future?  Maybe 
> some clamping diodes to keep the voltage on the digital pins in range?
>
> Walker
>
> On Tuesday, March 22, 2016 at 11:09:29 AM UTC-4, Wulf Man wrote:
>>
>> Power sequencing is the key. How are you doing this?
>> If you are applying the 5v to the pots first you may be causing the issue 
>> and blowing the processor pins.
>> All pins on the processor need to be isolated from everything until power 
>> rails are stable.
>> Drive a input pin when the processor is not fully powered on and you risk 
>> destroying the drivers in the chip.
>>
>>
>> Schematics of your design would help identify the problem.
>>
>>
>> On 3/22/2016 7:22 AM, Walker Archer wrote:
>>
>> Forgot to add info about how the cape is powered.  The chip I'm using on 
>> the cape is an AD5206 digital potentiometer (10k).  I'm using the 3.3v rail 
>> to power the SPI side and an external 5v (4.9v measured) supply powers the 
>> pots.  However, I've been getting voltages from the pots that aren't what 
>> I'd expect, so a few days ago I disconnected the 5v supply and ran the BBB 
>> 3.3v rail to a single pot just to see if the resulting voltages would make 
>> more sense.  Maybe that was what did it? 
>>
>> On Tuesday, March 22, 2016 at 10:15:53 AM UTC-4, Walker Archer wrote: 
>>>
>>> Thanks for responding Gerald.  The scope capture above was done with no 
>>> cape.  It was taken from SPI0.  The chip has one-way communication so I'm 
>>> only using SPID1 (P9_18 from memory).  The clock is coming from P9_22. 
>>>  Chip select is P9_17.  When I get home tonight I'll try the same from SPI1 
>>> and see if it's affected as well. 
>>>
>>>
>>>
>>> On Tuesday, March 22, 2016 at 9:39:30 AM UTC-4, Gerald wrote: 

 No way for me to tell what you may have done, but 1.8V is not good. Any 
 chance you can provide more information like the pin number and connector 
 you are using? 
 What do you have connected to this pin?
 How is that device powered?

 Gerald


 On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer  
 wrote:

> I've been building a custom cape for a robotics project and one of the 
> chips I'm using is controlled via SPI.  I've used an oscilloscope to 
> validate that the SPI is working as expected.  However, two days ago I 
> noticed that the chip stopped responding and after scoping the SPI signal 
> I 
> can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
> signal is still happening... and the clock signal is still at 3.3v.  It's 
> just the SPI data line that is only peaking at 1.8v. 
>
> So, I'm wondering if I've done something bad to my BBB or if I've 
> somehow triggered a feature that I don't know about yet.  I'm attaching a 
> photo of the oscilloscope screen that shows the issue.
> -- 
> For more options, visit 
> http://beagleboard.org/discuss
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 -- 
 Gerald
  
 ger...@beagleboard.org
 http://beagleboard.org/
 gco...@emprodesign.com

 -- 
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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

I suspect you're exactly right Wulf Man.  I was not really paying attention 
to the order I applied the power and I was assuming that the POT voltage 
would be isolated from the digital control side of the chip.  But I also 
assumed that if I blew the drivers that I would no longer get any signal 
from that pin.  Is it normal to get a reduced voltage?  I suppose I could 
almost fix the issue with an opamp (except I'd be worried that the 
defective pin would completely go dark someday.)

If I really did blow those pins then I'll get a good signal out of SPI1 
when I test it tonight.  How would I prevent this in the future?  Maybe 
some clamping diodes to keep the voltage on the digital pins in range?

Walker

On Tuesday, March 22, 2016 at 11:09:29 AM UTC-4, Wulf Man wrote:
>
> Power sequencing is the key. How are you doing this?
> If you are applying the 5v to the pots first you may be causing the issue 
> and blowing the processor pins.
> All pins on the processor need to be isolated from everything until power 
> rails are stable.
> Drive a input pin when the processor is not fully powered on and you risk 
> destroying the drivers in the chip.
>
>
> Schematics of your design would help identify the problem.
>
>
> On 3/22/2016 7:22 AM, Walker Archer wrote:
>
> Forgot to add info about how the cape is powered.  The chip I'm using on 
> the cape is an AD5206 digital potentiometer (10k).  I'm using the 3.3v rail 
> to power the SPI side and an external 5v (4.9v measured) supply powers the 
> pots.  However, I've been getting voltages from the pots that aren't what 
> I'd expect, so a few days ago I disconnected the 5v supply and ran the BBB 
> 3.3v rail to a single pot just to see if the resulting voltages would make 
> more sense.  Maybe that was what did it? 
>
> On Tuesday, March 22, 2016 at 10:15:53 AM UTC-4, Walker Archer wrote: 
>>
>> Thanks for responding Gerald.  The scope capture above was done with no 
>> cape.  It was taken from SPI0.  The chip has one-way communication so I'm 
>> only using SPID1 (P9_18 from memory).  The clock is coming from P9_22. 
>>  Chip select is P9_17.  When I get home tonight I'll try the same from SPI1 
>> and see if it's affected as well. 
>>
>>
>>
>> On Tuesday, March 22, 2016 at 9:39:30 AM UTC-4, Gerald wrote: 
>>>
>>> No way for me to tell what you may have done, but 1.8V is not good. Any 
>>> chance you can provide more information like the pin number and connector 
>>> you are using? 
>>> What do you have connected to this pin?
>>> How is that device powered?
>>>
>>> Gerald
>>>
>>>
>>> On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer  
>>> wrote:
>>>
 I've been building a custom cape for a robotics project and one of the 
 chips I'm using is controlled via SPI.  I've used an oscilloscope to 
 validate that the SPI is working as expected.  However, two days ago I 
 noticed that the chip stopped responding and after scoping the SPI signal 
 I 
 can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
 signal is still happening... and the clock signal is still at 3.3v.  It's 
 just the SPI data line that is only peaking at 1.8v. 

 So, I'm wondering if I've done something bad to my BBB or if I've 
 somehow triggered a feature that I don't know about yet.  I'm attaching a 
 photo of the oscilloscope screen that shows the issue.
 -- 
 For more options, visit 
 http://beagleboard.org/discuss
 --- 
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 Groups "BeagleBoard" group.
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 https://groups.google.com/d/optout.

>>>
>>>
>>>
>>> -- 
>>> Gerald
>>>  
>>> ger...@beagleboard.org
>>> http://beagleboard.org/
>>> gco...@emprodesign.com
>>>
>>> -- 
> For more options, visit http://beagleboard.org/discuss
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>
>

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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

There are no other SPI chips on that bus.  Since the AD5206 is permanently 
a slave on the SPI bus I would think it would not try to drive the line.

On Tuesday, March 22, 2016 at 10:55:49 AM UTC-4, Harvey White wrote:
>
> On Tue, 22 Mar 2016 05:47:19 -0700 (PDT), you wrote: 
>
> >I've been building a custom cape for a robotics project and one of the 
> >chips I'm using is controlled via SPI.  I've used an oscilloscope to 
> >validate that the SPI is working as expected.  However, two days ago I 
> >noticed that the chip stopped responding and after scoping the SPI signal 
> I 
> >can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
> >signal is still happening... and the clock signal is still at 3.3v.  It's 
> >just the SPI data line that is only peaking at 1.8v. 
>
>
> Had a chip (Epson S1D13781) with an SPI interface.  Had a similar 
> problem when sharing the SPI interface with another chip.  Bottom line 
> was that, unlike the standard SPI chips where the chip gets completely 
> off line when not selected, this chip *always* (the Epson) drives MISO 
> line low. 
>
> I was getting about 1.8 volts or so maximum voltage out of the 
> paralleled chip because it was trying to pull up a driver that was 
> stuck at zero.   
>
> Not sure that you have exactly the same problem, but is the chip 
> you're driving somehow trying to drive this line (and shouldn't)? 
>
> Harvey 
>
> > 
> >So, I'm wondering if I've done something bad to my BBB or if I've somehow 
> >triggered a feature that I don't know about yet.  I'm attaching a photo 
> of 
> >the oscilloscope screen that shows the issue. 
>
>

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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[evilwulfie]

Power sequencing is the key. How are you doing this?
If you are applying the 5v to the pots first you may be causing the
issue and blowing the processor pins.
All pins on the processor need to be isolated from everything until
power rails are stable.
Drive a input pin when the processor is not fully powered on and you
risk destroying the drivers in the chip.


Schematics of your design would help identify the problem.


On 3/22/2016 7:22 AM, Walker Archer wrote:
> Forgot to add info about how the cape is powered.  The chip I'm using
> on the cape is an AD5206 digital potentiometer (10k).  I'm using the
> 3.3v rail to power the SPI side and an external 5v (4.9v measured)
> supply powers the pots.  However, I've been getting voltages from the
> pots that aren't what I'd expect, so a few days ago I disconnected the
> 5v supply and ran the BBB 3.3v rail to a single pot just to see if the
> resulting voltages would make more sense.  Maybe that was what did it?
>
> On Tuesday, March 22, 2016 at 10:15:53 AM UTC-4, Walker Archer wrote:
>
> Thanks for responding Gerald.  The scope capture above was done
> with no cape.  It was taken from SPI0.  The chip has one-way
> communication so I'm only using SPID1 (P9_18 from memory).  The
> clock is coming from P9_22.  Chip select is P9_17.  When I get
> home tonight I'll try the same from SPI1 and see if it's affected
> as well.
>
>
>
> On Tuesday, March 22, 2016 at 9:39:30 AM UTC-4, Gerald wrote:
>
> No way for me to tell what you may have done, but 1.8V is not
> good. Any chance you can provide more information like the pin
> number and connector you are using?
> What do you have connected to this pin?
> How is that device powered?
>
> Gerald
>
>
> On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer
>  wrote:
>
> I've been building a custom cape for a robotics project
> and one of the chips I'm using is controlled via SPI. 
> I've used an oscilloscope to validate that the SPI is
> working as expected.  However, two days ago I noticed that
> the chip stopped responding and after scoping the SPI
> signal I can see that the BBB is sending the SPI data
> pulses at 1.8v.  The SPI signal is still happening... and
> the clock signal is still at 3.3v.  It's just the SPI data
> line that is only peaking at 1.8v.
>
> So, I'm wondering if I've done something bad to my BBB or
> if I've somehow triggered a feature that I don't know
> about yet.  I'm attaching a photo of the oscilloscope
> screen that shows the issue.
> -- 
> 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 https://groups.google.com/d/optout
> .
>
>
>
>
> -- 
> Gerald
>  
> ger...@beagleboard.org
> http://beagleboard.org/
> gco...@emprodesign.com
>
> -- 
> For more options, visit http://beagleboard.org/discuss
> ---
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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Harvey White]

On Tue, 22 Mar 2016 05:47:19 -0700 (PDT), you wrote:

>I've been building a custom cape for a robotics project and one of the 
>chips I'm using is controlled via SPI.  I've used an oscilloscope to 
>validate that the SPI is working as expected.  However, two days ago I 
>noticed that the chip stopped responding and after scoping the SPI signal I 
>can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
>signal is still happening... and the clock signal is still at 3.3v.  It's 
>just the SPI data line that is only peaking at 1.8v.


Had a chip (Epson S1D13781) with an SPI interface.  Had a similar
problem when sharing the SPI interface with another chip.  Bottom line
was that, unlike the standard SPI chips where the chip gets completely
off line when not selected, this chip *always* (the Epson) drives MISO
line low.

I was getting about 1.8 volts or so maximum voltage out of the
paralleled chip because it was trying to pull up a driver that was
stuck at zero.  

Not sure that you have exactly the same problem, but is the chip
you're driving somehow trying to drive this line (and shouldn't)?

Harvey

>
>So, I'm wondering if I've done something bad to my BBB or if I've somehow 
>triggered a feature that I don't know about yet.  I'm attaching a photo of 
>the oscilloscope screen that shows the issue.

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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

Forgot to add info about how the cape is powered.  The chip I'm using on 
the cape is an AD5206 digital potentiometer (10k).  I'm using the 3.3v rail 
to power the SPI side and an external 5v (4.9v measured) supply powers the 
pots.  However, I've been getting voltages from the pots that aren't what 
I'd expect, so a few days ago I disconnected the 5v supply and ran the BBB 
3.3v rail to a single pot just to see if the resulting voltages would make 
more sense.  Maybe that was what did it?

On Tuesday, March 22, 2016 at 10:15:53 AM UTC-4, Walker Archer wrote:
>
> Thanks for responding Gerald.  The scope capture above was done with no 
> cape.  It was taken from SPI0.  The chip has one-way communication so I'm 
> only using SPID1 (P9_18 from memory).  The clock is coming from P9_22. 
>  Chip select is P9_17.  When I get home tonight I'll try the same from SPI1 
> and see if it's affected as well.
>
>
>
> On Tuesday, March 22, 2016 at 9:39:30 AM UTC-4, Gerald wrote:
>>
>> No way for me to tell what you may have done, but 1.8V is not good. Any 
>> chance you can provide more information like the pin number and connector 
>> you are using?
>> What do you have connected to this pin?
>> How is that device powered?
>>
>> Gerald
>>
>>
>> On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer  
>> wrote:
>>
>>> I've been building a custom cape for a robotics project and one of the 
>>> chips I'm using is controlled via SPI.  I've used an oscilloscope to 
>>> validate that the SPI is working as expected.  However, two days ago I 
>>> noticed that the chip stopped responding and after scoping the SPI signal I 
>>> can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
>>> signal is still happening... and the clock signal is still at 3.3v.  It's 
>>> just the SPI data line that is only peaking at 1.8v.
>>>
>>> So, I'm wondering if I've done something bad to my BBB or if I've 
>>> somehow triggered a feature that I don't know about yet.  I'm attaching a 
>>> photo of the oscilloscope screen that shows the issue.
>>>
>>> -- 
>>> 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 https://groups.google.com/d/optout.
>>>
>>
>>
>>
>> -- 
>> Gerald
>>  
>> ger...@beagleboard.org
>> http://beagleboard.org/
>> gco...@emprodesign.com
>>
>>

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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

Thanks for responding Gerald.  The scope capture above was done with no 
cape.  It was taken from SPI0.  The chip has one-way communication so I'm 
only using SPID1 (P9_18 from memory).  The clock is coming from P9_22. 
 Chip select is P9_17.  When I get home tonight I'll try the same from SPI1 
and see if it's affected as well.



On Tuesday, March 22, 2016 at 9:39:30 AM UTC-4, Gerald wrote:
>
> No way for me to tell what you may have done, but 1.8V is not good. Any 
> chance you can provide more information like the pin number and connector 
> you are using?
> What do you have connected to this pin?
> How is that device powered?
>
> Gerald
>
>
> On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer  > wrote:
>
>> I've been building a custom cape for a robotics project and one of the 
>> chips I'm using is controlled via SPI.  I've used an oscilloscope to 
>> validate that the SPI is working as expected.  However, two days ago I 
>> noticed that the chip stopped responding and after scoping the SPI signal I 
>> can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
>> signal is still happening... and the clock signal is still at 3.3v.  It's 
>> just the SPI data line that is only peaking at 1.8v.
>>
>> So, I'm wondering if I've done something bad to my BBB or if I've somehow 
>> triggered a feature that I don't know about yet.  I'm attaching a photo of 
>> the oscilloscope screen that shows the issue.
>>
>> -- 
>> 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 https://groups.google.com/d/optout.
>>
>
>
>
> -- 
> Gerald
>  
> ger...@beagleboard.org 
> http://beagleboard.org/
> gco...@emprodesign.com 
>
>

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Re: [beagleboard] BBB Broken? SPI signal is at 1.8v

[Gerald Coley]

No way for me to tell what you may have done, but 1.8V is not good. Any
chance you can provide more information like the pin number and connector
you are using?
What do you have connected to this pin?
How is that device powered?

Gerald


On Tue, Mar 22, 2016 at 6:47 AM, Walker Archer  wrote:

> I've been building a custom cape for a robotics project and one of the
> chips I'm using is controlled via SPI.  I've used an oscilloscope to
> validate that the SPI is working as expected.  However, two days ago I
> noticed that the chip stopped responding and after scoping the SPI signal I
> can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI
> signal is still happening... and the clock signal is still at 3.3v.  It's
> just the SPI data line that is only peaking at 1.8v.
>
> So, I'm wondering if I've done something bad to my BBB or if I've somehow
> triggered a feature that I don't know about yet.  I'm attaching a photo of
> the oscilloscope screen that shows the issue.
>
> --
> For more options, visit http://beagleboard.org/discuss
> ---
> You received this message because you are subscribed to the Google Groups
> "BeagleBoard" group.
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> email to beagleboard+unsubscr...@googlegroups.com.
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>



-- 
Gerald

ger...@beagleboard.org
http://beagleboard.org/
gcol...@emprodesign.com

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[beagleboard] BBB Broken? SPI signal is at 1.8v

[Walker Archer]

I've been building a custom cape for a robotics project and one of the 
chips I'm using is controlled via SPI.  I've used an oscilloscope to 
validate that the SPI is working as expected.  However, two days ago I 
noticed that the chip stopped responding and after scoping the SPI signal I 
can see that the BBB is sending the SPI data pulses at 1.8v.  The SPI 
signal is still happening... and the clock signal is still at 3.3v.  It's 
just the SPI data line that is only peaking at 1.8v.

So, I'm wondering if I've done something bad to my BBB or if I've somehow 
triggered a feature that I don't know about yet.  I'm attaching a photo of 
the oscilloscope screen that shows the issue.

-- 
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