Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > sci.electronics.design > #453581
| From | rickman <gnuarm@gmail.com> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: Output boards, SPI vs I2C |
| Date | 2017-03-25 14:04 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <ob6b9p$9a2$1@dont-email.me> (permalink) |
| References | <ob4lm9$k58$1@reader1.panix.com> |
On 3/24/2017 10:46 PM, David Lesher wrote: > I pondering a microcontroller project that will need a number (say 24) > output relays. > > Is there a reason to use I2C over SPI? It looks like there are 8-channel > boards of both ilks, and I don't know if one has an advantage in this case. I2C is a serial bus (with a spec) with all devices connected in parallel. SPI is a functional description rather than a real spec, but is so simple it is not hard to make it work. SPI devices can be connected in parallel with separate select pins, or all in series being controlled as one long shift register. I2C runs at a basic rate of 100 kbps with a 400 kbps mode as well as faster modes at 1 Mbps and up. 400 kbps is generally supported, but the faster modes are not universal. SPI runs at whatever speed the devices work at. I2C has a protocol that you will need to program. SPI specified no protocol other than shifting data in and out. Any protocol is defined by the slaves you choose. All things being equal (whatever that means as I2C and SPI have very little equal) I would pick SPI for driving 24 relays because the "protocol" should be very simple (shift out the data) and I2C can be more complex to implement. I'd probably wire three boards serially and see if that works. If not, I would wire them in parallel with three separate chip selects. -- Rick C
Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-25 02:46 +0000
Re: Output boards, SPI vs I2C krw@notreal.com - 2017-03-24 23:25 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 04:13 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-25 14:04 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 04:11 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-26 02:37 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 14:41 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-26 12:47 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-26 19:49 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-27 10:49 -0400
Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-27 18:41 +0000
Re: Output boards, SPI vs I2C Martin Riddle <martin_ridd@verizon.net> - 2017-03-27 19:07 -0400
Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-28 08:03 +0000
Re: Output boards, SPI vs I2C Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-28 10:44 -0400
Re: Output boards, SPI vs I2C Jasen Betts <jasen@xnet.co.nz> - 2017-03-28 18:59 +0000
Re: Output boards, SPI vs I2C Martin Riddle <martin_rid@verizon.net> - 2017-03-28 15:37 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-04-03 17:49 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-04-03 15:18 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-04-04 02:59 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-04-04 00:54 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 05:08 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-28 02:16 -0400
Re: Output boards, SPI vs I2C Martin Riddle <martin_ridd@verizon.net> - 2017-03-27 19:03 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 03:28 +0000
Re: Output boards, SPI vs I2C rickman <gnuarm@gmail.com> - 2017-03-28 00:38 -0400
Re: Output boards, SPI vs I2C David Lesher <wb8foz@panix.com> - 2017-03-28 14:47 +0000
csiph-web