Oli Glaser wrote: > ----- Original Message ----- > From: "sergio masci" > To: "Microcontroller discussion list - Public." > Sent: Monday, May 24, 2010 3:43 AM > Subject: Re: [PIC] Using PIC to sample 90 wires > > > >> I have to agree with Russel, this would definately be the simplest >> solution and by far the quickest to implement software wise. >> > > While I don't "disagree" with Russell, the only problem I have with these > statements is the fact that no solution is going to be even vaguely "simple" > for a beginner. They will all include USB, which is pretty nasty to debug > even with the right tools, then there is the possible need for isolation > that could add a bit of hassle to the mix, so some form of isolated serial > comms may end up being used in the shift register solution anyway - 8+ opto > isolators for each SR? or one isolated SPI/USB interface?. Isolate the CMOS SR from PIC, only 3 optos. But you don't know isolation is needed. Serial USB on 18F using the ready to go JAL or C libraries seems simple. No harder than RS232. At least on JAL anyway. If I was needing isolation I'd use Russell's idea on 18F2550 skinny DIP. If I didn't like serial SR, I'd use 12 x 8 way switches, 3 address lines in parallel all switches and read 8 inputs on Port D and 4 inputs on Port B on 18F4550 40pin DIP. Though my initial thought was 12 x Octal tristate buffers. If no isolation, high volume and low part count I'd use 2x 18F87Jxx, maybe. We don't know enough about the volume , space constraints and application. if Each input is separate phone line then you actually need 96 opto isolators and can wire them in a 8 x 12 matrix direct to one PIC, maybe. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist