On Wed, Feb 9, 2011 at 7:20 PM, Nathan House wrot= e: > I changed the schematic to use the "standard" op-amp symbol. Is it > more readable now? > One thing I noticed, which has nothing to do with readability (which is quite good) is that the USB VCC pin goes no where. When you have a self powered PIC, you should monitor the status of the USB VCC pin so you don't have the pullups enabled on the D+ and D- lines when there is no USB VCC present. This can happen if the host computer goes to sleep or otherwise shuts down the USB controller. The microchip usb stack supports this feature, I think I remember it being defined in hardwareprofile.h. A typical circuit to do this is the put a 100K resistor from USB VCC to ground and then another 4.7K resistor from USB VCC to a pin configured as an input. The 100K resistor keeps the input pin from floating, and won't draw too much from the USB when it's on. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .