Subject:
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Re: Brainstorms
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 12 Aug 2002 05:39:55 GMT
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Viewed:
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933 times
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In lugnet.robotics, sjbaker1@airmail.net writes:
> Wayne Gramlich wrote:
>
> > The RoboBricks project was started 2-1/2 years ago. At that time,
> > there were no readily available and 8-pin microcontrollers with built
> > in I2C support.
>
> Are you sure? I thought Philips had teeny-tiny microprocessors with
> I2C at least 10 years ago...before the I2C bus switched speeds from 100kbps
> to 400kbps. I2C is about 20 years old.
They may have had them, but they didn't show up in any of the
catalogs I was looking at. Semiconductor companies are quite
notorious for deciding to stop production on various chips.
Lot's of people tried to standardize on the Motorola HC11
chips and Motorola basically stopped production. I restricted
my chip selection to chips for which I could get a programmer
and for which I thought there was a good chance they would
still be in production 5-10 years from now. I'm afraid that
Philips was never even considered.
> > My biggest problem with I2C is addressing. Each device needs
> > needs to have its address pins properly set.
>
> Address pins? What address pins?
Most chips that are designed around I2C have one or two
or three pins that are used to set some number of the device
address bits. For example, the standard I2C serial EEPROM's
use an address of 1010AAA, where AAA are the bits set on three
of the chip pins. Thus, you can have up to eight of these
chips on one bus. Or you can have another device with
an address of 10AAA01 and arrange to avoid conflicts.
In general, when people are designing printed circuit
boards that use I2C, they have to figure how to cram all
of the devices on the board *and* arrange to have the
parts not conflict with their addresses. I'm afraid that
I2C was never really meant to be an open ended bus where
people could plug I2D devices into and out of the bus.
That doesn't mean it can't be bent to that task, but there
is some real work and engineering involved.
Hopefully you are beginning to understand why I'm not as
enthusiastic about I2C as other people on this least
appear to be.
Later,
-Wayne
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Message is in Reply To:
 | | Re: Brainstorms
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| (...) Are you sure? I thought Philips had teeny-tiny microprocessors with I2C at least 10 years ago...before the I2C bus switched speeds from 100kbps to 400kbps. I2C is about 20 years old. (...) Address pins? What address pins? ---...--- Steve Baker (...) (22 years ago, 11-Aug-02, to lugnet.robotics)
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