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I2C & Power supply


I got an Axis developer board LX last week and start to
explore it.

Two questions came up to which I couldnt find answers
in the online doc and the list archive:


I found several answers concerning the I2C bus and the
possibilities to use it in this list, but most of them
seem to discuss the predesessor cpu without MMU and eLinux.

Am I right with this:

.) The Etrax 100LX has two pins dedicated to I2C
.) The protocol is implemented in software (in the
    I2C modules (drivers)
.) These two pins are not officially reachable on
    the Axis Developer Board LX but they would be
    available at the pins of the RTC chip.
.) There is another IO pin used to switch between
    the serial EEPROM (I2C conformant) and the RTC chip
    (using a simple non I2C protocol)
.) The RTC chip is of not much use since there is no
    battery to keep the time over power cycles.

So if I manage to grab the three signals at the RTC chip,
and connect my I2C components with a simple logic that
uses the switch signal to mask off the communication
with the RTC chip, could the I2C implementation be used
with the Developer board and the Linux 2.4.19 kernel
delivered with the board ?

Are there any other things that hinder the use of
the I2C interface ?

Is there an alternative way to connect I2C devices
allready explored and impelemented by someone ?

Power supply:

My device should be battery powered.

I found in the schematics that there should be
a point on the developer board where DC power can be
supplied as an alterantive to the AC power supply

Which Voltage should be suppiled and where to connect
the battery to ?

What average power consumption would I have to expect?

Thanks in advance for any ansewers,

Peter Mueller  Elimpex - Medizintechnik GesmbH.

Tel: +43-2236-41045-0   Fax: +43-2236-41045-9
mailto:peter.mueller@xxxxxxx.com http://www.elimpex.com/