> Robert Young wrote:
> > 1) RB6 / RB7 are the programming and debug pins.  Yes, you can use them as I/O but you will loose your ability to use them as debug pins.  Furthermore, you call out RB6 on your oddly shaped PIC twice.
> 
> Are you sure I have RB6 on it twice? I had a look around the chip and 
> can't find the second instance of it... please let me know!

I could be reading it wrong, the text is pretty darn small so B's can look like E's and vice versa.  Size and contrast ratio are your friends.

> 
> > 2) Component values not labeled in many cases.  What FET/MOSFET are you using?  Where is the value for the high and low side drivers?  Etc.
> >   
> 
> I don't need any of those details on the schematic. I'll get my board 
> made and then I'll have a think about it.

Yes you do need these details on the schematic...  One day you will wonder what those parts are.

> 
> > 3) No component numbering, again this can be a cause for confusion.  U1, U2, D1, D2, R1, etc are quite helpful.  -- Wait I retract part of that statement.  I found some components are labeled but so small they are hard to see.  And in some cases there are nets running through the text.  And finally some have a "number" but most just have "?".
> >   
> 
> I'll get around to that. Protel has this "auto numbering" thing that 
> will assign numbers for me. Where appropriate, I'll change the names to 
> something more intuitive.
> 

No experience with Protel.  Some schematic entry number as you go, some auto number.  Personally I use Eagle and it autonumbers as I go but then I can go back later and change manually or run a script to renumber from the schematic or the board.  My preference is to renumber from the board so that things start in the upper left corner and read in increasing order left to right / top to bottom.

> > 5) Power?
> >   
> 
> At the moment I'm think of going from a 9 V square battery into an 
> LM7805. I'll get around to that in due course.

It will be important eventually...

> 
> > 6) Ground?
> >   
> 
> Em... eh... the negative of the supply...  ?

Yep.

> 
> > 7) Supply bypass caps?
> >   
> 
> What are they?

In the grand tradition of the PICLIST, RTFM. :)  All kidding aside, you should bone up on that topic ASAP.

> 
> > 8) Reset component values?  Not familiar with the 16F887 but in general, for the "newer" PICs (16F and 18F) I was of the impression that a single pull-up resistor on MCLR/VPP is OK for the reset if you also have the POR bit set.  For a production unit I'd think a bit more about the reset vs power supply turn on but for hobby and play seems OK.
> >   
> 
> I don't know about this stuff. I'll ask questions in due course.

I think most PIC datasheets have a little section on reset signal generation.  May not be sufficient information if you aren't familiar with what can happen though.

> 
> > 9) Pins for the 7-seg?  Are you going to use something like a 74HC595 and SPI bus to control them?
> >   
> 
> Do you see the net names I put on the pins for the seven segs? Those 
> nets go to the output of the high-side driver. (I originally did it by 
> just drawing wire but it was way too messy).

Again, I missed those due to the size of the text.  Does Protel have a BUS function?  You can collect several related signal names, say LED0 to LED7 into something like LED[0..7] and then use a thicker BUS line to indicate they all run along parallel.

> 
> > 10) I've never been a big fan of the weak-pull ups in PORTB and unless I'm really pressed for power consumption I like a nice stiff pull up resistor.  Again, _personal_ preference but I generally use a 47K for pull ups on a 5V design unless I need to minimize power and then I go through the exercise of computing currents versus expected duty cycle of the signal vs. input current HI/LO logic for the given PIC and its operating environment.  For the one you have indicated on E1, what value?
> >   
> 
> Haven't thought about it yet. I'll wait til I get my board. Probably 
> something like 10k though.
> 
> > 11) What is hanging off of E2?
> >   
> It's a piezo speaker :-D

> 
> > 12) Internal oscillator?  If nothing else, a quite note in the corner of the schematic about that.
> >   
> 
> I still have RB6 and RB7 free so I'm thinking of hooking up some sort of 
> 20 MHz yoke-a-ma-jiggy to it.

I think you mean RA6 and RA7.

> 
> > 13) Un-used inputs on your driver chips should probably be tied to ground.  Maybe through a resistor so you can use them later if you decide you want them.
> >   
> 
> Nice, thanks for that. It would have slipped my mind.
> 
> > 14) If you switch to a common cathode 7-seg you could use your two spare high side drivers instead of the discrete FET/MOSFETs shown.
> >   
> 
> VERY NICE! Never crossed my mind! I'll look into it  :-D
> 
Rob

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