At 05:20 PM 6/24/99 -0700, you wrote: try a 74c154 4 line to 16 line decoder or a cd14514 (hint: use the bit 0 and bit 1 inputs to generate the req'd strobe pulse 4514 only)- requires 4 to 6 pins but 4 to 5 are reusable >A nice way to make a diode matrix like this is to sandwich the diodes >between two pieces of stripline experiment board (diodes standing up and the >strips on both pieces of board 90 degrees rotated) > >another idea to make a code like this is to take an old eprom , program it >with your table and hook the address lines up to your switch (dont forget >the output enable line(s)) > >Peter > >pvh@vertonet.com >peter_van_hoof@hotmail.com >peter_van_hoof@mad.scientist.com > > >>From: John Perkinton >>Reply-To: pic microcontroller discussion list >>To: PICLIST@MITVMA.MIT.EDU >>Subject: Re: Best way to interface a 12 pos rotary switch >>Date: Thu, 24 Jun 1999 14:24:23 +0100 >> >>Multiplex your lines then you can get it down to 4 input lines. Use diodes >>to multiplex them, and remember to pull the lines high either with >>resistors, or internal pull ups if using PortB. >> >>I use this circuit in a microphone paging console giving me 31 buttons into >>5 lines of an input port. And because it only uses 1n4148 diodes to >>multiplex it it costs very little. >> >>I've included a schematic as a wmf file. >> >>It is great for rotary switches, as it has only one common line, unlike >>most >>keypad multiplexing circuits, which scan the keys as rows and columns. >>----- Original Message ----- >>From: Ross Bencina >>To: >>Sent: Wednesday, June 23, 1999 3:39 PM >>Subject: Best way to interface a 12 pos rotary switch >> >> >> > Hi PICsters, >> > >> > I have a 12 position single pole rotary switch that I'd like to >>interface >>to >> > a 16F84 and I don't have 12 spare IO pins ;) (Ideally I'd like to use 4 >>pins >> > or less). I've seen examples of using a resistor lader and an RC timer >> > circuit (uses too much cpu time for my purposes), presumably there's >>also >>a >> > logic chip (demux?) that will do the job, I'm just wondering if I've >>missed >> > any other obvious, minimal, and/or clever solutions to this problem. >> > >> > Thanks in advance. >> > >> > Ross B. >> > ................................. >> > http://www.audiomulch.com/~rossb/ >> > >><< multi.wmf >> > > >_______________________________________________________________ >Get Free Email and Do More On The Web. Visit http://www.msn.com