> Would this count as a very simple operating circuit for a dsPIC33 FJ 128 > GP 802? > Assumption: > - VDD is connected to 3.3 V > - VSS is connected to GND > - The capacitor is an electrolytic capacitor of 10 uF (positive end of > cap is facing VDDCORE, negative end is facing GND) > > http://img197.imageshack.us/img197/4023/dspiccircuit.png 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). Russell McMahon ----- Original Message ----- From: "solarwind" To: "PICLIST" Sent: Wednesday, June 24, 2009 2:49 PM Subject: [PIC] Very simple operating circuit > Would this count as a very simple operating circuit for a dsPIC33 FJ 128 > GP 802? > > Assumption: > - VDD is connected to 3.3 V > - VSS is connected to GND > - The capacitor is an electrolytic capacitor of 10 uF (positive end of > cap is facing VDDCORE, negative end is facing GND) > > http://img197.imageshack.us/img197/4023/dspiccircuit.png > > I'm planning to make a PCB for it but I'm new to dsPICs > > > -- [ solarwind ] -- http://solar-blogg.blogspot.com/ > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist