On Monday, January 19, 2015 at 6:23:49 PM UTC-8, john3909 wrote: > From: maxmike <[email protected]> > Reply-To: "[email protected]" <[email protected]> > Date: Monday, January 19, 2015 at 5:10 PM > To: "[email protected]" <[email protected]> > Subject: [beagleboard] Same wire going to adc and comparator kills interrupts > > > > I have the output of an op amp go directly to the BBB adc and the values are > read correctly. > But, the same wire is going to a comparator to generate interrupts. > It looks like the comparator is not firing all the way to ground because of > the adc drag. > I thought of placing a 1K resistor from the adc input to ground but that does > nothing. > Anything higher is going to bother the adc. I'm stumped. > Well, it depends on the opamp. Some opamps are not able to drive all the way > to 0V, but as long as it goes below the logic low for your I/O input, it > shouldn’t matter. If you really want an opamp that goes to zero, choose one > that is capable to operating rail to rail. Also, the opamp feedback circuit > is important because you are going to want some hysteresis or your GPIO input > might see some noise close to the trigger point. > > > Regards, > John > > > > > -- > > 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]. > > For more options, visit https://groups.google.com/d/optout.
The lmv762 comparatorworks 100% if I sever its input from the adc - it's only when the adc is tied to it that it does't go to ground at the output. -- 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]. For more options, visit https://groups.google.com/d/optout.
