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 <warch...@gmail.com> >>>> 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> >>>>> 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> >>>>> https://groups.google.com/d/optout. >>>>> >>>> >>>> >>>> >>>> -- >>>> Gerald >>>> >>>> ger...@beagleboard.org >>>> <http://beagleboard.org/>http://beagleboard.org/ >>>> gco...@emprodesign.com >>>> >>>> -- >> 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. >> >> >> -- 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+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
