AVR I2C/TWI mit getrenntem -IN und -OUT benutzen

Hi

>Bei Atmel finde ich nur:

> SCLIN Serial Clock In for TWI when external driver interface is enabled
> SCLOUT Serial Clock Out for TWI when external driver interface is
>enabled
> SDAIN Serial Data In for TWI when external driver interface is enabled
> SDAOUT Serial Data Out for TWI when external driver interface is
>enabled

Wo?

MfG spess

zB hier:
http://www.atmel.com/images/Atmel-8387-8-and16-bit-AVR-Microcontroller-XMEGA-A4U_Datasheet.pdf

servaz

Hi

Dazu steht nur ein kleiner Absatz im XMEGA AU MANUAL:

21.7 Enabling External Driver Interface

An external driver interface can be enabled. When this is done, the 
internal TWI drivers with input filtering and slew rate
control are bypassed. The normal I/O pin function is used, and the 
direction must be configured by the user software.
When this mode is enabled, an external TWI compliant tri-state driver is 
needed for connecting to a TWI bus.
By default, port pins 0 (Pn0) and 1 (Pn1) are used for SDA and SCL. The 
external driver interface uses port pins 0 to 3 for
the SDA_IN, SCL_IN, SDA_OUT, and SCL_OUT signals

Da die Pins dann nur normale IO-Pins sind (ohne Slewrate-Control und 
Input Filter) ist wohl ein externer Treiber notwendig der das ganze 
wieder zum 2-Draht-Interface macht.

MfG Spess

Hi

Im Manual unter

21.2 Overview

Gibt es auch noch einen Hinweis:

It is possible to disable the TWI drivers in the device, and enable a 
four-wire digital interface for connecting to an external
TWI bus driver. This can be used for applications where the device 
operates from a different VCC voltage than used by
the TWI bus.

MfG Spess

Vielen Dank fürs Finden! Was müssen die das auch einmal mit und einmal 
ohne Unterstrich benennen. Machts nicht leichter.

Kennt jemand so einen "external TWI compliant tri-state driver"?

servaz

Ah nein. mea culpa.

21.8.1 CTRL – Common Control register
Bit0: EDIEN

0 Normal TWI Two-pin interface, slew rate control, and input filter.
1 External driver interface Four-pin interface, standard I/O,
  no slew rate control, and no input filter.