Thanx Quentin! I went to the site and read some "perplexing and scary" things. Like, waving a License Application in my face. Like, the FAQs all being about how you have to submit a formal application to a Central Scrutinizer who assigns codes, and something about how if the address code was already used, you still have to pay for the application process... Could it really be possible that I'd have to go thru any of this even once -- let alone *four* times, once for each -- for a one-off project like this (a PIC-controlled 3-octave mini chimes)?? ;-} I must be missing something obvious here. Could someone please humor a complete newbie to I2C and give me a wee bit of insight into how I would know what code to send to address a specific one of 36 l/O pins spread across four PC8574P's ? Any general info on l2C links, hardcopy resources, projects, parts sources etc. would also be greatly appreciated if you have it close at hand. I need to start getting up to speed. My obvious knowledge deficit aside, this does look like an elegant solution for my I/O needs, with the added benefit of learning about what looks like a daw-gone flexible system capable of managing a whole host of peripheral-related applications. Thanks for pointing me towards l2C! bOO ======================== From: Quentin Subject: Re: Ding Dong! > There are a few ways to do it (multiplexing with logic IC's, etc.) but > when I need to expand my I/O's, I use I2C. > http://www-us2.semiconductors.philips.com/i2c/ > will give you lots of information. >... For 36 I/O on say a 16F84, I would use 4x PC8574P... > Of course, if you haven't done it yet, you'll have to learn how to I2C. > But once you know it, it opens a new world of possibilities for the PIC. >