> -----Original Message----- > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf > Of David Cary > Sent: 24 March 2008 05:34 > To: piclist@mit.edu > Subject: [SX] Bean's SX28 8x8 PWM Code and SX28 Addressable > > > your limit per serial wire depends on how you approach it. > > That's certainly true. > But I am mystified as to why so many people "hardcode" addresses into > firmware -- that requires a custom version of the code for every chip > on the serial network. > I am also mystified as to why so many people "use a dip switch", which > requires a bunch of pins to read the dip switch. > > Why don't these people use "scalable" networking protocols that scale > up to an unlimited number of chips? > Protocols that work fine with identical firmware in every chip, and > only require a maximum of the "serial data in" pin plus 2 or so other > pins on the master and each slave, even if there are dozens of slaves? > > Off the top of my head, here are 3 such protocols: > (Pick whichever one protocol is the easiest for you to implement). > (Please tell me about other "scalable" "simple" networking protocols, > especially non-proprietary open standards). > > * daisy-chain serial SPI: (4 wires per slave; automatic baud rate > synchronization) approach used by, among other things, JTAG scan. > > * decrement packet address: (2 wires per slave > > * daisy-chain select, common data: (3 wires per slave) Unless I have misunderstood, all of these would appear to suffer from increasing latency the further away from the host the slave is in the network. With a large number of slave devices this could be unacceptable. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist