> > > > *1. Very minor references in most BBB documentation/webpages discussing > Analog Inputs and max voltages. Coming from working with Pi's and > Arduino's, it was common to have analog inputs range from 0 to 5V, so the > 1.8V was unexpected.*
Not sure where you're going on this one, but that problem is all on you. I'm not an EE, and even I know better than to start hooking up *ANYTHING* without first reading official documentation. Where the official documentation is the beaglebone reference manual, as well as the TRM for the A335x. So if you're trying to blame someone else for your screw up . . . well it's going to fall on deaf ears. What more, 1.8v is an absolute maximum. Meaning; you'd be lucky to not blow the processor if going to 1.81v. Anyway, like Harvey said above, you have to scale input voltages, and then that also gets scaled in software. On Mon, Jun 6, 2016 at 11:03 AM, Harvey White <[email protected]> wrote: > On Mon, 6 Jun 2016 10:12:43 -0700 (PDT), you wrote: > > >Hi, > > > >Yesterday I was trying to use some of the analog inputs on the BBB to read > >my photodiode, and instead, I think I blew up the power supply on my > board. > >With power applied, I get no PWR led, so I'm pretty certain it's dead. > >Short of replacing the power management chip, is there anything I can > >do/replace to get the board working again? > > > > > >Brief Background > > > >I hooked up the photodiode to an Arduino and was able to read 0 - 5V > >easily, so I wanted to do the same on the BBB. > >I read some of the materials re: AIN on the BBB, but apparently I missed > >all the references to the max voltage of 1.8V! > >I started by enabling the analog inputs on the BBB, and started with AIN0. > > > >With nothing attached, I was reading about 0 - so far, so good. > >Then I figured I'd try to see what a full 5.0V read out, so I plugged in > >the VDD 5V to AIN0, and all the LEDs went out instantly. > >Now all LEDs stay off, even the PWR LED, when power is applied. > > > >No doubt, it was stupid, but I have a few additional takeaways - > >1. Very minor references in most BBB documentation/webpages discussing > >Analog Inputs and max voltages. > >Coming from working with Pi's and Arduino's, it was common to have analog > >inputs range from 0 to 5V, so the 1.8V was unexpected. > > Actually, it's 0 to VCC on the MEGA and XMEGA chips. The Mega chips > can run at 3.3 volts, and the XMEGA chips *must* run at no more than > 3.3 volts. > > > > >2. Isn't there any protection at all from this kind of damage? Or was > the > >main problem that I used the VDD 5V and fed it into the AIN0 port? > > These are generally direct chip inputs, and there's generally no > buffering. > > >Would I have killed it if I used the VDD ADC instead of the VDD 5v or > would > >using the VCC ADC possibly have protected it? > > 1.8 volts maximum. > > > > >3. What is the "normal" way of using the BBB analog inputs with 5V > levels? > > Is it possible - or is there where I would use a level-shifter or zener > >diode? > > Level shifters are generally digital, and zener diodes don't help all > that much (and are not really a good idea here). My standard advice > would be to run the analog voltage through a non-inverting op amp > configured as a gain stage. You run the op-amp (and have to pick one > that does rail to rail and also runs from 1.8 volts) from the 1.8 volt > supply. > > Harvey > > > > >Thanks for the any comments or additional info provided! > > > -- > 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 [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/hbeblb1809orgk011t8crt9ucj3m942qlm%404ax.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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORoh0R%2BFq6C4%3DY_0qwUzf5kTYzRSHc1-oc%2Bfy2ip4Wi7Jg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
