On Wed, Jun 24, 2009 at 5:25 AM, Russell McMahon wrote: > Very simple - yes. > Operating - sometimes, maybe, depending on assumptions which may have been > made but which are not shown on the diagram. > > Not showing all assumptions made makes it hard for people to provide useful > comment. (Putting SOME of them in an added list is a good start but showing > them on the circuit even better). > > Re other query re capacitor size - you need to read the reasonably extensive > prior discussions on decoupling capacitors or look at a good web reference, > of which there will be thousands. The "how big should a capacitor be" > question is often asked and almost as often answered. Having somebody tell > you it's not too crucial (it's not) is not a substitute for looking around > at what is done and learning why. As 'another list member' pointed out > recently, lack of understanding and proper treatment of decoupling > capacitors is a major source of probelms. I don't think he put it quite that > way :-).And, more caps often don't hurt. Avdd to Avss may benefit from such. > or may not, sometiomes. > > Hardware terminating /MCLR in any of the several approved manners is > generally held to be superior to disabling it in software, where that is an > option. (Where it's not an option then doing it in hardware is a *REALLY* > good idea :-) ). > > With such a capable device it would be usual to use an external crystal or > clock source. ie if you are using a DSPIC then it won't be long before you > would like the clock frequency to be moderately accurately known and stable. > Providing for a crystal and not using it at first works better than not > providing for it and wanting to use one. > > Diagram and reality never correlate 100% but note that it may be better to > run all ground traces directly to the common ground point than to chain them > as shown. AVss especially is provided separately for good reason. This being > a dsPIC you may care more in this case than in many others. Ground currents > flowing in the common ground path will appear as signal to the analog > circuitry if built as shown. Gargoyle knows all about this. For many > applications this may not make a vast difference but as it's as easy to do > right as wrong you might as well get in the habit of doing it pedantically > against the day when you need to care. > > You may wish to group some ISP pins on a header. > > Beyong minimalist, but you MAY want to provide options for SIP resistor > packs of high resistance pull up/downs for some pins to make the software > rogours less demanding. If you are well disciplined at ensuring the software > matches the hardwrae (nothing floats without a pull [up|down], all > unterminated pins are outputs, analog functions are disabled when not used > and allowed for appropriately in hardware, ...]. > > ie it's just another processor and indeed just another IC whose pins must be > terminated correctly as per spec sheet - but it has a bit wider definition > of "correctly" than say a 74HC14 (gotta love those Schmitt imputs). Wow - I just want it to work :( For my PIC18F2620, all I did is hook up ICSP pins, UART pins, a decoupling cap and it worked. I'm asking (in a similar fashion) how to quickstart with the dsPIC with minimal fuss and minimal components. That is, other than 3 caps, would anything else be REQUIRED to get it up and running? (I have PICKIT2 hooked up to ICSP and UART lines to MAX233A) I ask because I see all these new pins (AVSS, AVDD, VDDCORE) that I don't really know what to do with... Sure, there's the datasheet, but it's so BIG, that it's easy to miss something. Also, for such a simple quickstart circuit, I was hoping someone could provide, short, concise answers. It shouldn't be too much of a problem since the circuit IS simple and it's just to get started (program hello world code and see it on my terminal). -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist