"what harm does a ramp do to a PIC input? Excess power dissepation?" This would be a nice, quick test to perform: 1. monitor Vcc (Vdd?) supply to PIC with a) millimammeter (perhaps no more than a 1 Ohm R and a DVM) and b) a scope 2. using a function gen apply either a saw-tooth or sine wave to an unused PIC-input pin 3. Observe test instruments for any observable indications. RF Jim ----- Original Message ----- From: "Scott Thomas" To: Sent: Monday, September 16, 2002 9:47 AM Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc) Agreed. But what harm does a ramp do to a PIC input? Excess power dissepation? Scott -----Original Message----- From: Roman Black [mailto:fastvid@EZY.NET.AU] Sent: Monday, September 16, 2002 10:28 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Infrared Communications -- (variable freq 555 osc) Correct! :o) The voltage at the "discharge" pin of the 555 will rise as a ramp (as the cap charges) which is not really a good idea for a PIC input. And diodes like 1N4148 cost only 1 cent! -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.