Post by thread:[PIC] I2C vs SPI vs Microwire

I've seen quite a bit of traffic dealing with I2C, but what about SPI? Is there a method to bit-bang for SPI? To be honest, I'm just starting to look at this, so I don't have any specs. But if someone has some code snippets, that would be nice. ____________________________________________________________________ Get free email and a permanent address at http://www.netaddress.com/?N=1

SPI is easier since you don't have ACK/NAK/STOP/START to deal with. Just CS, CLK, DO, and DI. It's a lot simpler if you just look at the wave forms. The problem is that there are so many flavors. I've found it best to just bit bop whatever is in the data sheet. Andy Hardware Engineering <spam_OUTpic-ineerTakeThisOuTUSA.NET> on 06/12/2000 03:26:13 PM Please respond to pic microcontroller discussion list <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> To: PICLISTKILLspamMITVMA.MIT.EDU cc: (bcc: Andrew Kunz/TDI_NOTES) Subject: [PIC] I2C vs SPI vs Microwire I've seen quite a bit of traffic dealing with I2C, but what about SPI? Is there a method to bit-bang for SPI? To be honest, I'm just starting to look at this, so I don't have any specs. But if someone has some code snippets, that would be nice. ____________________________________________________________________ Get free email and a permanent address at http://www.netaddress.com/?N=1

YOu wrote: >I've seen quite a bit of traffic dealing with I2C, but what about SPI? Is >there a method to bit-bang for SPI? To be honest, I'm just starting to look >at this, so I don't have any specs. But if someone has some code snippets, >that would be nice. > I have no code for you, but in my experience SPI is **much** easier to deal with than I2C. First, the exact coding is somewhat chip dependent. I've done both SPI A/D and D/A converters, and the requirements were different. Secondly, it generally takes at 1-2 extra lines, used for chip enable/etc. Third, generally there is no special protocol, but just flick CS, and send out 8 or 16 SPI clocks while reading/writing. I have I2C bit-bang code taking about 250 bytes, involving about 6-8 RAM variables, and custom SPI code of about 20 bytes, no RAM variables, and which took about 10 minutes to write. Few grey hairs result from using SPI, in my experience. - Dan Michaels Oricom Technologies http://www.sni.net/~oricom ==========================

A good book which contains SPI code samples is "Serial PIC'n" by Roger L. Stevens. You can read my review of the book here: http://ubasics.com/adam/books/ser_picn.shtml The book talks about both bit-bang SPI, and on chip SPI with real-world examples (master, slave, A/D chips, display driver, data logger, daisy chaining SPI devices, etc) as well as other serial communications ( I2C, Microwire, 1-wire, RS-232, etc) While I certianly would love it were you to buy it from amazon through the links on my site (I get a buck or two), Peter Andersen sells it in the amazon zShops for about $10 less than amazon sells it. Use the link on my site to look at the amazon listing, and just under the listing it'll show you similar products available in the zShops, one of which will be the less expensive version. -Adam Hardware Engineering wrote: > > I've seen quite a bit of traffic dealing with I2C, but what about SPI? Is > there a method to bit-bang for SPI? To be honest, I'm just starting to look > at this, so I don't have any specs. But if someone has some code snippets, > that would be nice. > > ____________________________________________________________________ > Get free email and a permanent address at http://www.netaddress.com/?N=1