in AT91RM9200 is TWI two wire interface compatible with I2C standard ?

If yes, I wonder why this was not declared in the datasheet ?

Thanks for your attention.

Hi Misha,
as far as i know the TWI and the I2C are compatible. Perhaps they are the same.

But it is "cheaper" to say TWI as I2C (trademark).

Best regards,
Edi

Misha

I use the TWI interface on a number of I2C devices with no problem. I usually run at 400kHz but also on one device (old) at 100kHz.

The TWI interface needs pulling high via a couple of 2.2k resistors and I found that the addition of two 10pF caps to load the lines helped with an occasional power on problem.

I believe the term I2C is a copyright to Philips. Hence atmels term TWI.

Hope this helps.

Simon

This sure will help me - Thank you again.

Thanks for your prompt replay....

Simon,

Are you sure it is possible to use both speeds on the bus ?
In my opinion you have to choose the speed of the slower device unless it will be 'disturbed' by faster messages on the bus.
I have currently a problemm similar to yours.
I had 2 fast devices (EEPROM, RTC) on the bus and I had to add another old slow one (IO expander Philips PCF8574). I had (too) strongs pullups on the bus : 1kO.
I configured the bus to 100kHz. The IO expander didn't respond. I had to change the pullups to 4.7kO in order to soften the timings to make the expander work. It seems a little bit bizare to me for the moment ...

Jean-Jacques

Jack

It did work for me !. It took me a long time to sort it all out though and the bus termination was critical. I also found the order on the bus was important, or rather in one arrangement it worked (slower device very close to master) and in another case (slower device on end of bus next to terminators) it didn't.

I added a checksum to my memory so for every read I made sure it had worked. All a bit messy.

I also found that if I power cycled too fast (didn't let the 3.3v decay to 0) then the TWI bus would fail completely on next reset.

As soon as possible I changed to all 400kHz and wont do it again.

Hope it helps and you find a work around.

Simon