🚀 go-pugleaf

Yep, I used an I2C bus system about 3 yrs ago, so my
recollection is a little vague, but it is a 3-wire
serial data protocol with an arbitration system.
The three lines were CLOCK, DATA, <something else - GND??>
and you could have at least one MASTER device, and several
SLAVE devices. We used only one master, so I never investigated
the multimaster facility (if it existed!), and the protocol
consists of the master looking at the lines to see if they
are floating, and if they are it asserts an address which
corresponds to a particular slave (slaves have the address
hardwired in).  If the slave needs data, then this is sent too.
The clock is used to synchronise the data.  Then the slave can
reply with some response.  The data speed goes up to about
500Kbits/s, I think. The maximum length of the bus line should
not exceed about 2 metres or so because signals are asserted as
LOW=0V, HIGH=Floating->5V.

This is intended as a VERY ROUGH GUIDE!!!  The information
above should all be checked up - I did not design any I2C
stuff, I just sent addresses and data to the I2C software that
another guy wrote.  The master, in our case, was a 6303
processor and the I2C was controlled by some general I/O lines.
We used it to run a Mullard teletext controller/acquisition chip and a
TV tuner chip - I forget the numbers.

POINTS TO NOTE:

The I2C protocol driver for one master was written in under a
day, so it isn't too difficult.

All device types that are used on the I2C bus will have a
unique address code, which is shown in the data book for the
device.  Some (all?) also have another address, selectable by a
pin, which can be used if you want two devices on the bus.

Hope this is of some help, sorry I cannot recall more, but I
don't have any of the design sheets anymore.  Have fun!

                        ... Bill

************************************************************************
Bill Witts, CS Dept.     *    Nel Mezzo del cammin di nostra vita
UCL, London, Errrp       *    mi ritrovai per una selva oscura
william@cs.ucl.ac.uk     *    che la diritta via era smarrita.
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