I2C port IO chips
Ralph Malph
chips other than Philips. Seems to get most of their I2C parts, you
have to buy a couple thousand minimum. I am looking for a way to add 8
or 16 IOs. Some chips are port expanders, some are LED drivers; either
will work if they come in small packages.
So who else makes I2C chips? A google search turned up lots of stuff,
but no I2C makers.
moocowmoo
news:400EB0D4...@yahoo.com...
You could roll your own out of an AVR or PIC. Plenty of I2C examples out
there.
Peter
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Andy Sinclair
>I looked around the web and could not find any sources of I2C port IO
>chips other than Philips. Seems to get most of their I2C parts, you
>have to buy a couple thousand minimum.
Have you checked usual distributors?
I don't know where you are but places like Farnell sell them.
Andy
Rene Tschaggelar
Beside that it can be done with IO ports in PICs and AVRs,
it could also be done with a small CPLD.
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Lewin A.R.W. Edwards
> or 16 IOs. Some chips are port expanders, some are LED drivers; either
> will work if they come in small packages.
I2C is patented/copyrighted/trademarked. Look for '2-wire interface' parts, maybe.
jim granville
TI second source the PCF8574.
http://focus.ti.com/docs/prod/folders/print/pcf8574.html
They also seem to have dropped their prices....
Maxim have a range of IO exanders, with SPI and i2c versions.
There are also SMbus devices, and SMbus is a PC variant of i2c.
Unlike i2c masters, Slave i2c devices generally need some HW support -
take a look at the Cygnal uC & Philips LPC9xx families, as most of these
have i2c HW support, and many of the smaller uC these days price compare
reasonably with the dedicated i2c IO options.
-jg
Ralph Malph
Sell what, Philips chips? I am in the US. I believe Farnell is
Australia, right?
I could go to a lot of different distributors, but other than Philips, I
don't know of any parts. All the distis I have checked only sell
Philips parts in large quantities. I guess I could ask for a few dozen
samples. So far Arrow is being very obliging. They sent me a couple
hundred $.25 capacitors.
Meindert Sprang
>
> Sell what, Philips chips? I am in the US. I believe Farnell is
> Australia, right?
No, Europe.
> I could go to a lot of different distributors, but other than Philips, I
> don't know of any parts. All the distis I have checked only sell
> Philips parts in large quantities. I guess I could ask for a few dozen
> samples.
Try the US-counterpart of Farnell: Digikey.
www.digikey.com
Do a search for the PCF8574AN and you'll find they have 415 in stock and
sell for $2.00 a piece.
Meindert
Alaric B Snell
Is '2-wire interface' always actually I2C, if avoiding the trademark issue?
I see a lot of SPI devices around - Would I be right in thinking that
SPI is faster than I2C? Is it *better*?
ABS
CBarn24050
least 400khz.
Tilmann Reh
As already mentioned, PCF8574 should be available in distribution.
(At least here in Europe, it is, in rather small quantities, and even
at hobby-electronic vendors.)
I2C is slower than other serial interfaces, but the advantages are
multi-master and fewest wires.
If you need cheap and rather fast I/O expansion, and have a few more
wires, try using simple shift registers ('165 for input, '595 for
output) - you can cascade them easily, and often you can share some
signals with other peripherals.
--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de
==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)
Lewin A.R.W. Edwards
>
> Is '2-wire interface' always actually I2C, if avoiding the trademark issue?
I'm hesitant to say "yes". It's not officially I2C unless it's logo'd.
Really, you have to look at the datasheet for the part. If you are
bit-banging, it doesn't make much difference, does it?
> I see a lot of SPI devices around - Would I be right in thinking that
> SPI is faster than I2C? Is it *better*?
SPI is different. I2C is great for addressing "registered" components
scattered around a board without introducing large PCB routing
problems. By "registered" I mean, devices that contain a few control
registers but don't handle constant bulk transfers. For example, an
I2C-controlled digital pot controlling the contrast voltage on an LCD.
You set it occasionally.
SPI is more efficient for "streaming" devices such as audio codecs,
where there is a small amount of setup and then the device spends most
of its life sinking or sourcing a constant stream of data.
SPI is also somewhat easier to work with from a bit-banger's
perspective. And it's easy to isolate; you can also keep dead
peripherals off-bus with a simple switch controlled by the device's
select line (whereas in I2C you either need an intelligent buffer chip
in between slave and bus, or you need to rely on the slave's port
working right).
The above comments are of course at least partly subjective.
Marcin E. Hamerla
Use 596 for outputs. Thet are much cheaper, easier to buy and their
footprint is smaller.
--
Pozdrowienia, Marcin E. Hamerla
- What about your soul?
- I'm an engineer.
Alaric B Snell
>>>I2C is patented/copyrighted/trademarked. Look for '2-wire interface' parts, maybe.
>>
>>Is '2-wire interface' always actually I2C, if avoiding the trademark issue?
>
>
> I'm hesitant to say "yes". It's not officially I2C unless it's logo'd.
> Really, you have to look at the datasheet for the part. If you are
> bit-banging, it doesn't make much difference, does it?
Ah, but I don't plan on bit-banging :-) There's a hardware I2C interface
in the LPC2106, for example, and it also matters if one is wishing to
have multiple devices on the same bus.
Perhaps "interoperable with I2C devices" is a better wording ;-)
> SPI is more efficient for "streaming" devices such as audio codecs,
> where there is a small amount of setup and then the device spends most
> of its life sinking or sourcing a constant stream of data.
I've noticed the protocol does seem to let a master keep control of the
bus for an arbitrary number of bytes - is that the root of the
difference you're referring to? Plus the chip select thing means that
there's no addressing overhead. At the cost of more traces on the board
and more I/O pins used, even if you use a 3-8 or 4-16 decoder :-/
I've looked at CAN, as well. I see uPs with CAN interfaces built in, and
CAN interface chips that are external to uPs. I get the impression it's
mainly used to communicate between uPs rather than as a uP -> device
control bus.
What I would *love* *love* *love* to see is a big directory of I2C,
"2-wire", SPI, and (if they exist) CAN peripherals, all on one site if
possible, so I can really compare what's available. My favourite
semiconductor catalogues organise ICs by function rather than interface,
making it awkward to really build up a picture of what's available in my
head. Philip's site has a listing of all their I2C devices, which is a
start, though.
> The above comments are of course at least partly subjective.
Like so much in life - but thanks for satisfying my curiousities :-)
ABS
Ralph Malph
>
> Ralph Malph schrieb:
> >
> > I looked around the web and could not find any sources of I2C port IO
> > chips other than Philips. Seems to get most of their I2C parts, you
> > have to buy a couple thousand minimum. I am looking for a way to add 8
> > or 16 IOs. Some chips are port expanders, some are LED drivers; either
> > will work if they come in small packages.
> >
> > So who else makes I2C chips? A google search turned up lots of stuff,
> > but no I2C makers.
>
> As already mentioned, PCF8574 should be available in distribution.
> (At least here in Europe, it is, in rather small quantities, and even
> at hobby-electronic vendors.)
>
> I2C is slower than other serial interfaces, but the advantages are
> multi-master and fewest wires.
> If you need cheap and rather fast I/O expansion, and have a few more
> wires, try using simple shift registers ('165 for input, '595 for
> output) - you can cascade them easily, and often you can share some
> signals with other peripherals.
Thanks for your post, and all the others as well. Once I was clued into
the fact that I should be searching for "SMB" and "2wire interface", I
found several other companies that make I2C stuff (or SMB which is
nearly identical).
I originally wanted to use shift registers. But I need something that
does not flop the outputs around as you are shifting in as well as being
5 volt tolerant and very small. The 74xx594 would be perfect, but it is
not being made in the newer technologies. I prefer the QFN package and
not many parts are currently available in that yet. In fact, I found
that although TI and Philips second source each other and both have QFN
packaging for their logic, they use *different* QFN packages. I can't
think of why TI is using a larger width for their package. In fact one
of the data sheets I had showed a 2.5 mm QFN, but all the other
references TI has show the 3.5 mm package. If it is not second sourced,
I am much less likely to use it.
So there are many sources for I2C IO port chips. I think I can even
find some that meet all my requirements and are second sourced which
makes life so much easier. The fact that I can get many of them from
sources like Digikey is the icing on the cake for doing the prototypes.
:)
Ralph Malph
>
> Ralph Malph napisal(a):
>
> >I looked around the web and could not find any sources of I2C port IO
> >chips other than Philips. Seems to get most of their I2C parts, you
> >have to buy a couple thousand minimum. I am looking for a way to add 8
> >or 16 IOs. Some chips are port expanders, some are LED drivers; either
> >will work if they come in small packages.
> >
> >So who else makes I2C chips? A google search turned up lots of stuff,
> >but no I2C makers.
>
> Use 596 for outputs. Thet are much cheaper, easier to buy and their
> footprint is smaller.
I think you are referring to the 74xx596. This chip would be good
except for two things. 1) it does not have a clear on the output
register, and 2) it is only availble as an LS part. I don't want to use
technology that is that old and a 5 volt part is not compatible with
much else on the board.
But then in a long search, I found the TPIC6B596 which is very
interesting. But the smallest package is a 20 pin SO. The price is
right, $.56 @ 1000.
simon
> but no I2C makers.
OnSemi make a JLC1562, which is essentially pin compatible with the
8574, and adds a 6 bit DAC.
Beware though that the SMD part is 0.2" wide, and the 8574 is 0.3"
wide.
btw we will have a couple of simple PCBS that take 8574 / 1562's
available in a week or so..
Simon
www.i2cchip.com
Albert Lee Mitchell
> I looked around the web and could not find any sources of I2C port IO
> chips other than Philips. Seems to get most of their I2C parts, you
> have to buy a couple thousand minimum. I am looking for a way to add 8
> or 16 IOs. Some chips are port expanders, some are LED drivers; either
> will work if they come in small packages.
I think we have a few hundred PCF8574's on the shelf available at less
than commercial prices. Contact me directly for details.
> So who else makes I2C chips? A google search turned up lots of stuff,
> but no I2C makers.
Also search for 'SMD' as 'IIC' is copyrighted by Philips. We've made I2C
peripherials out of Atmel parts in the past which permits smart
peripherials but limits the bus speed to about 65khz instead of the
100/400khz.
-- Regards, Albert
----------------------------------------------------------------------
AM Research, Inc. The Embedded Systems Experts
http://www.amresearch.com 916.780.7623
----------------------------------------------------------------------
Ralph Malph
>
> > So who else makes I2C chips? A google search turned up lots of stuff,
> > but no I2C makers.
>
> OnSemi make a JLC1562, which is essentially pin compatible with the
> 8574, and adds a 6 bit DAC.
> Beware though that the SMD part is 0.2" wide, and the 8574 is 0.3"
> wide.
On may make good parts, but they have the worst web site I have seen
other than the Asian companies. I did a search on "I2C Bus I/O
Expander" and came up with >700 hits. There is no way to further filter
or do an advance search. All I can do is try to come up with more
keywords, which I actually think would give me *more* hits since they
seem to be doing an OR rather than an AND of the words.
How can smart people like ON semi be so dumb?