Forums

I2C master

Started by David Lesher September 22, 2017
In theory, I2C handles multiple masters.
<https://www.i2c-bus.org/MultiMaster/>

Wonder if anyone is doing so, and if so, how hard was it to get up & running?

-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
David Lesher wrote on 9/22/2017 2:59 PM:
> In theory, I2C handles multiple masters. > <https://www.i2c-bus.org/MultiMaster/> > > Wonder if anyone is doing so, and if so, how hard was it to get up & running?
There are two features in I2C that I believe are seldom implemented. One is clock stretching and the other is multiple masters. I don't know, but suspect you are looking at a long row to hoe. -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
rickman <gnuarm@gmail.com> writes:

>David Lesher wrote on 9/22/2017 2:59 PM: >> In theory, I2C handles multiple masters. >> <https://www.i2c-bus.org/MultiMaster/> >> >> Wonder if anyone is doing so, and if so, how hard was it to get up & running?
>There are two features in I2C that I believe are seldom implemented. One is >clock stretching and the other is multiple masters. I don't know, but >suspect you are looking at a long row to hoe.
Thanks, we'll eschew. RS-232 may be old and slow but works.... -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close.......................... Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
David Lesher wrote on 9/22/2017 7:32 PM:
> rickman <gnuarm@gmail.com> writes: > >> David Lesher wrote on 9/22/2017 2:59 PM: >>> In theory, I2C handles multiple masters. >>> <https://www.i2c-bus.org/MultiMaster/> >>> >>> Wonder if anyone is doing so, and if so, how hard was it to get up & running? > >> There are two features in I2C that I believe are seldom implemented. One is >> clock stretching and the other is multiple masters. I don't know, but >> suspect you are looking at a long row to hoe. > > Thanks, we'll eschew. RS-232 may be old and slow but works....
It's also not multi-master... I guess you can roll your own. -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
"rickman" <gnuarm@gmail.com> wrote in message 
news:oq49e4$tqk$1@dont-email.me...
>> Thanks, we'll eschew. RS-232 may be old and slow but works.... > > It's also not multi-master... I guess you can roll your own.
RS-485 is a solved problem, cheap, and noise tolerant. Or CAN, if you don't mind a little more hardware (often provided in MCUs) and more automation as far as the bus dealing with bus-y problems all by itself. These might be a little hungry, or overly robust. If you need lower current consumption, and the signal doesn't have to leave the board, an open collector bus (like I2C) is still a good idea. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
On Fri, 22 Sep 2017 18:59:30 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>In theory, I2C handles multiple masters. ><https://www.i2c-bus.org/MultiMaster/> > >Wonder if anyone is doing so, and if so, how hard was it to get up & running?
If you have *any* other choice. Don't go there. There be demons there.
On Fri, 22 Sep 2017 16:13:53 -0400, rickman <gnuarm@gmail.com> wrote:

>David Lesher wrote on 9/22/2017 2:59 PM: >> In theory, I2C handles multiple masters. >> <https://www.i2c-bus.org/MultiMaster/> >> >> Wonder if anyone is doing so, and if so, how hard was it to get up & running? > >There are two features in I2C that I believe are seldom implemented. One is >clock stretching and the other is multiple masters. I don't know, but >suspect you are looking at a long row to hoe.
Clock stretching is rather common. It's used in the various I2C extension interfaces like the LVDS video interfaces (Maxim or TI) and things like A2B (ADI).
Tim Williams wrote on 9/22/2017 10:42 PM:
> "rickman" <gnuarm@gmail.com> wrote in message > news:oq49e4$tqk$1@dont-email.me... >>> Thanks, we'll eschew. RS-232 may be old and slow but works.... >> >> It's also not multi-master... I guess you can roll your own. > > RS-485 is a solved problem, cheap, and noise tolerant. Or CAN, if you don't > mind a little more hardware (often provided in MCUs) and more automation as > far as the bus dealing with bus-y problems all by itself. > > These might be a little hungry, or overly robust. If you need lower current > consumption, and the signal doesn't have to leave the board, an open > collector bus (like I2C) is still a good idea.
RS-485 is an electrical interface, nothing more. It doesn't solve the multi-master problem any more than RS-232 does. -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998
"rickman" <gnuarm@gmail.com> wrote in message 
news:oq4oif$20s$1@dont-email.me...
> RS-485 is an electrical interface, nothing more. It doesn't solve the > multi-master problem any more than RS-232 does.
Well, RS-232 is an anti-solution, as it's always asserted. Point to point only. There's a reason I said 485 and not 422. As for the protocols traditionally used on these interfaces, asynchronous serial with some kind of bus arbitration is standard on 485. For some strange reason, when you search on "RS-485", you get not just the signaling standard, but also a lot of protocols that people use on it... ;-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Tim Williams wrote on 9/23/2017 12:55 AM:
> "rickman" <gnuarm@gmail.com> wrote in message > news:oq4oif$20s$1@dont-email.me... >> RS-485 is an electrical interface, nothing more. It doesn't solve the >> multi-master problem any more than RS-232 does. > > Well, RS-232 is an anti-solution, as it's always asserted. Point to point > only. There's a reason I said 485 and not 422. > > As for the protocols traditionally used on these interfaces, asynchronous > serial with some kind of bus arbitration is standard on 485. > > For some strange reason, when you search on "RS-485", you get not just the > signaling standard, but also a lot of protocols that people use on it... ;-)
There are plenty of networks based on RS-232. As you say, a little searching helps a lot. But giving an electrical standard reference is nothing like actually giving some useful information on the networking issue. -- Rick C Viewed the eclipse at Wintercrest Farms, on the centerline of totality since 1998