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RE: I2C multimaster with devboard 82


There is hardware support for multimaster I2C but as far as I know it
not been used by anyone. It may help to make sure that 
CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C is off (multi master won't work with
it enabled but I can't guarantee that it will work with it disabled)


-----Original Message-----
From: owner-dev-etrax@xxxxxxx.com">mailto:owner-dev-etrax@xxxxxxx.com] On
Behalf Of Martin.Daublebsky@xxxxxxx.net
Sent: Friday, September 19, 2003 5:59 PM
To: dev-etrax
Subject: I2C multimaster with devboard 82

I am trying to realize an I2C-bus-communication with
-PIC-Controller as a master
-EEPROM as a slave
-Devboard 82 as another master.

This means that two master are performing I/O-operations on the EEPROM
I2C-bus. We are using the dedicated I2C-pins of the axis-board (PB0 and

Now we saw on the oscilloscope that there are sometimes collisions,
the axis-board does not recognize if the bus is already used by the PIC
PIC does recognize if the bus is used by the axis-board).
Furthermore the level of SCL never reaches LOW-level if the axis-board
HIGH-level (what it has to do in the idle-time), even if the PIC drives
to LOW.
This lead us to the assumption that
1. there is no pull-up resistor used on the SCL-line on the axis-board
2. there is no busy-detection in the i2c-driver implemented.

My question is if there already exists a multimaster-i2c-driver or if we
have to modify the existing one ourself. And why is there no
on the SCL-line? Well, it works in the single-master-mode, but it is not

Best regards