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 > --- > 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/ > 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+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@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.
