> > Here's my current schematic:> > http://freepdfhosting.com/uploads/6640a7ea8a.pdf> > The PDF file is high resolution so you can zoom in.> > Here's my first question:> 1) Do I need the RC circuit on the Vpp pin of the 887? I heard something > about being able to use an internal pull-up?> 2) I remember someone saying something about putting capacitors across > the power supply as well... so if you could please give me pointers on that.> Your switcher won't work, in fact it will probably die pretty quick. The Feedback pin needs to be held around 1.24V. That isn't an inductor between Vin and SW1. What it is I don't know but it isn't an inductor. Look up the symbol and update schematic. You show a standard diode for the output, it might work but the average diode is too slow. You should use a Schottkey diode. 1N5818 maybe, jellybean cheap and easy to get. I think that is the standard recomendation in the LT datasheets. Value for current limit resistor? Value for input cap? Value for output cap? In fact, you may need more than one output cap, a large and a small both designed to deal with a particular part of the output transients from the switcher. Not only the capacitance value, but the material type (ceramic, tant. etc), voltage rating, ESR and "quality" rating (NP0, COG, etc) are importatnt with switchers. Not doing any analog work in this one so you can live with some ripple so long as it is less than 500mV and faster than any scanning frequency in your LEDs. That said, you might be able to monitor your own battery voltage by re-arranging some pins to free up RA0. You could watch for a dying battery pack (say trip at 2.5V). But if you do this, you might need to learn more about supply bypassing and also add a little averaging and hysteresis to the ADC results so you don't get fasle positives. You don't need the RC circuit shown on the Vpp line. A single pull up resistor is sufficient for non-commercial designs. Size it such that when Vpp is present, you aren't going to try and push lots of current into the Vdd node. For a commercial design, a reset/voltage monitor chip might be a better idea. Still don't have comonent values various places. No connect on pin 32? No connect on pin 31? Data sheet not handy to me but that doesn't seem right. No bypass caps. Again, I think wikipedia has some information. And a rule-of-thumb for PICs is one 0.1uF per Vdd connection and one bulk capacitor, say 10uF. Keep in mind these could also be part of the output network from your switcher too. MOSFET/FET not labled. Tying the LEDs to the 3V means as the batteries fade, the LEDs will dim. If you tie them to the +5V the step-up switcher (assuming sufficient output current, that is still open for debate) will keep you at a constant current with your resistor per LED setup. You can keep your total current quite low if you multiplex the LED drives fast enough for persistance of vision to take over and make it all look steady state. Off the cuff remark about your LED connections, if you have both the matrix and 7seg on at the same time you will see various LEDs dim a bit and brighen a bit as more or fewer are turned on. Might not be particularly noticable, or it might be very distracting. PROTEL (I think that is what you said you were using) is letting you draw your schematic in a wierd way. If you want a nifty, and free schematic and layout package, Eagle is nice. But its interface will be just as bonkers and non-standard as you may already find PROTEL. Such is the way of the world. Still, you are making some progress. Rob -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist