That's exactly why I want to come up with a little saner way to pull up PORT_EN. It's way too easy to just touch the wrong side of that resistor, or something else in the area. It's begging to happen some percentage of the time even if you know what the problem is and are careful.
On Wed, Oct 18, 2017 at 8:05 PM, Brian Brindle <bbrin...@gmail.com> wrote: > Josh, > > I looked at one of the REX boards I had that didn't work. The regulator > was getting hot on it and I had the same low resistance measurements on the > VCC and ground. I know on this particular one I killed the CPLD by shorting > the FTDI VCC and ground when jumping VCC to R3. > > Brian > > On Oct 18, 2017 7:22 PM, "Brian White" <bw.al...@gmail.com> wrote: > >> I guess if you're going to build over 60 of them it starts to matter. I >> just figured if I'm going to go to this much effort it took just to build >> one at all, that $1 wasn't even visible, but a built and in-use rex that >> fails some day when it might have lived, is visible. So I went for the >> better-ish versions of all parts. The factors for this are not the same as >> for mass producing a clock that will sell in dollar stores. >> >> On Wed, Oct 18, 2017 at 6:39 PM, Stephen Adolph <twospru...@gmail.com> >> wrote: >> >>> Commercial is fine.... >>> >>> >>> On Wednesday, October 18, 2017, Josh Malone <josh.mal...@gmail.com> >>> wrote: >>> >>>> Also, meant to ask: >>>> >>>> Brian's BOM includes the Industrial variant of the CPLD. The >>>> commercial variant is almost $1 cheaper and seems well within >>>> tolerance >>>> >>>> (voltage min is 3 instead of 2.7, temp is 0 - 70 C instead of 40 - 85 >>>> °C) >>>> >>>> >>>> Any reason not to sub this part in? >>>> >>>> -Josh >>>> >>>> On Wed, Oct 18, 2017 at 4:56 PM, Josh Malone <josh.mal...@gmail.com> >>>> wrote: >>>> > Thanks. I'm going to just order new parts and try again. >>>> > >>>> > On Wed, Oct 18, 2017 at 4:49 PM, Brian Brindle <bbrin...@gmail.com> >>>> wrote: >>>> >> 11.7k on 2 of mine. >>>> >> >>>> >> >>>> >> On Oct 18, 2017 4:25 PM, "Stephen Adolph" <twospru...@gmail.com> >>>> wrote: >>>> >>> >>>> >>> I can try to measure it later today for you. >>>> >>> >>>> >>> On Wed, Oct 18, 2017 at 4:24 PM, Stephen Adolph < >>>> twospru...@gmail.com> >>>> >>> wrote: >>>> >>>> >>>> >>>> either the chip is a dud, or you have soldered it down in the wrong >>>> >>>> orientation (which is kinda easy to do)... Do you have more CPLDs? >>>> >>>> >>>> >>>> On Wed, Oct 18, 2017 at 4:22 PM, Josh Malone < >>>> josh.mal...@gmail.com> >>>> >>>> wrote: >>>> >>>>> >>>> >>>>> Thanks for the leads. >>>> >>>>> >>>> >>>>> I removed the CPLD and the resistance from 3v3 to gnd went to >>>> open; >>>> >>>>> repopulated it and it went to 3-ohms. Dunno what to try next. >>>> Maybe >>>> >>>>> put the same CPLD back on an original REX board (non-castellated) >>>> and >>>> >>>>> see what happens. But, I'd *really* love for someone to measure >>>> the >>>> >>>>> resistance on a known-good REX board and let me know what it >>>> should >>>> >>>>> be. Assuming the CPLD draws <= 1ma (datasheet says 17uA standby), >>>> R >>>> >>>>> should be over ~3k. >>>> >>>>> >>>> >>>>> -Josh >>>> >>>> >>>> >>>> >>>> >>> >>>> >> >>>> >>> >>
