Hysteresis on dsPIC ports?
in [Design]
|
From: WangoTango on 27 Jan 2010 15:30 In article <7sbhbmFt77U1(a)mid.individual.net>, invalid(a)invalid.invalid says... > WangoTango wrote: > > In article <7sbcbtFv25U1(a)mid.individual.net>, invalid(a)invalid.invalid > > says... > >> > >>> Now on the subject of noise, I have learned that interfacing microns in an industrial environment requires > >>> *always* special precautions. > >>> I use opto couplers myself always, simply because that > >>> 1) gets rid of ground loops. > >>> 2) allows for a wide range of input voltages, say you get something from a 24 V system, or 48 V, or even 230 V. > >>> 3) you can likely use the micros internal pullups at the input. > >>> 4) Very high frequency RF does not make it through an optocoupler. > >>> 5) no capacitive coupling to speak of either. > >>> etc etc. > >>> So, be smart, and use those. > >> > >> It ain't so easy in price-sensitive gear (consumer and so on) where > >> every penny counts. If you can make it happen with a buck less than the > >> other guy your client wins :-) > > > > A buck less AND it has to work. > > > It will. > > > > Is what you are working on going to be produced in such vast numbers > > that 25 cents here or there is going to be the difference between making > > or breaking the profit margin? > > I find that a reliable product is a lot easier to sell than one that is > > just 'cheap'. > > > > This one just has to be small. I can make uC products work very reliably > without fancy circuitry around them, have done it many times. _If_ the > uC is properly characterized, which this one is not. I would not have > picked it but was already in there. I'm not doubting your abilities, just we know what the constant is, the uC, and everything else goes from there.
From: Jan Panteltje on 27 Jan 2010 15:41 On a sunny day (Wed, 27 Jan 2010 11:22:02 -0800) it happened Joerg <invalid(a)invalid.invalid> wrote in <7sbi2vF1itU1(a)mid.individual.net>: >Joel Koltner wrote: >> "Joerg" <invalid(a)invalid.invalid> wrote in message >> news:7sbhbmFt77U1(a)mid.individual.net... >>> This one just has to be small. I can make uC products work very >>> reliably without fancy circuitry around them, have done it many times. >>> _If_ the uC is properly characterized, which this one is not. I would >>> not have picked it but was already in there. >> >> What's the cost of fixing the many flaky internal power-on reset >> circuits that you've seen many of? :-) >> > >In terms of components? Well under 50c, even in IC form. These little >dudes are quite nice at around 15c a pop in qties: > >http://www.onsemi.com/pub_link/Collateral/NCP302-D.PDF PICs have that all build in :)
From: WangoTango on 27 Jan 2010 15:47 In article <hjq8f0$eji$1(a)news.albasani.net>, pNaonStpealmtje(a)yahoo.com says... > On a sunny day (Wed, 27 Jan 2010 11:22:02 -0800) it happened Joerg > <invalid(a)invalid.invalid> wrote in <7sbi2vF1itU1(a)mid.individual.net>: > > >Joel Koltner wrote: > >> "Joerg" <invalid(a)invalid.invalid> wrote in message > >> news:7sbhbmFt77U1(a)mid.individual.net... > >>> This one just has to be small. I can make uC products work very > >>> reliably without fancy circuitry around them, have done it many times. > >>> _If_ the uC is properly characterized, which this one is not. I would > >>> not have picked it but was already in there. > >> > >> What's the cost of fixing the many flaky internal power-on reset > >> circuits that you've seen many of? :-) > >> > > > >In terms of components? Well under 50c, even in IC form. These little > >dudes are quite nice at around 15c a pop in qties: > > > >http://www.onsemi.com/pub_link/Collateral/NCP302-D.PDF > > PICs have that all build in :) > Yep, turn on the PUT, the WDT, the BOR, and you have a pretty damn good chance of powering up in a known state. Turn on the OSC fail interrupt and you are really cooking with gas.
From: Joel Koltner on 27 Jan 2010 16:02 "WangoTango" <Asgard24(a)mindspring.com> wrote in message news:MPG.25ca7071767c861498ae89(a)news.east.earthlink.net... > Yep, turn on the PUT, the WDT, the BOR, and you have a pretty damn good > chance of powering up in a known state. Turn on the OSC fail interrupt > and you are really cooking with gas. Will PICs do "failover" to an internal RC clock if the xtal (or other external clock input) doesn't fire up? I used some MSP430s a large handful of years ago that did that, and thought it was pretty slick. We use some Atmel AVRs at work that have this "tacked on" ability to use a 32kHz crystals as a very-low-power oscillator for a timer (generally to wake the processor up from sleep). It works, but it's nowhere near as elegant as what you could do with MSP430s. ---Joel
From: Joerg on 27 Jan 2010 16:05
Jim Thompson wrote: > On Wed, 27 Jan 2010 10:07:59 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >> >> [...] >> >>> So far, no response from the E-mail I sent to Microchip :-( >>> >> Not too surprising. Thanks for sending the email. >> >> Foundries are a lot more responsive. For one of them I sent the NDA >> yesterday afternoon and during the night they tossed me the keys to the >> process data. Plus they are processing some sort of design kit order, >> whatever than means. Another one immediately scheduled a conference call >> for early this afternoon. Now that's customer service. >> >> >>> Looking at some old Atmel stuff that was purely digital, it should be >>> about 300mV with a 3.3V supply. >>> >>> Can't you test it ?:-) >>> >> Yes but the hardware is currently 1500 miles from here. However, that >> won't help too much because I need to know the guaranteed minimum >> hysteresis. >> >> >>> BTW: The hysteresis can have it's center located anywhere between >>> 0.2*VDD and 0.8*VDD. >>> >> That would be no problem. > > They've probably never measured it, just inserted a library part ;-) > > You _do_ know that you can safely put an R/C in front of a Schmitt > input to get rid of large HF noise? > Yes, but there comes a point where you introduce too much external latency when doing that. > I came up with that VT/VBE from rail hysteresis gimmick (posted > earlier today) during my ignition pick-up days... around 40 years > ago... rejects even severe spark noise ;-) > My last ignition thingie was end of last year. But it's for a flying apparatus and not cars :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |