solarwind wrote: > On Wed, Jun 24, 2009 at 6:57 AM, solarwind wrote: > >> On Wed, Jun 24, 2009 at 5:25 AM, Russell McMahon wrote: >> >> > > Don't get me wrong, your long, detailed explanation is much > appreciated, but for someone who's diving into a very different chip > for the first time, it can be overwhelming. > You're right... it can be overwhelming. So, realize that and read the datasheet so that the problems are not as overwhelming as they could be. I have never used the dsPIC33 series chips, but, not suprisingly, the datasheet says a bunch of things that show your initial design is *very* flawed. Specifically, it says (in section 2.1): (the chip) requires attention to a minimal set of device pin connections before proceeding with development. The following is a list of pin names which must always be connected ... (and then it lists pins and required connections...). Now, of those required connections... it specifically states that all Vdd/Vss AVdd/AVss pins, the MCLR, The Vcap/Vddcore, the PGECx and PGEDx pins, the OSC* pins if you use a crystal, and potentially the Vref+/-. It also says that all Vdd/Vss and AVdd/AVss pairs *must* be decoupled. The use of decoupling capacitors on every pair of power supply pins, such as VDD, VSS, AVDD and AVSS is required (per section 2.2). Further, it makes recommendations for what capacitors to use for the decoupling, where to place them, and the VCap capacitor. Now, your original design has no connections to MCLR, no crystal (perhaps not required), has no decoupling caps (which section 2.2 says you need 3 of - which should be 0.1uF ceramic as per recommendation), and the spec says in section 2.3 that the VCap capacitor *must* be between 4.7 and 10uF of the 16V type and can be ceramic or tantalum (not *electrolytic* like you suggest). The trace between the device and this cap should be no longer than 6mm. Now, what is more overwhelming.... reading the datasheet, or trying to find out why things don't work? Speechless. Rolf -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist