TWI code example for two AVR

Does it really have to be I2C?

SioL

Master->Slave

something

between

ok.

yes I have to use TWI, if its what u mean

There is a good example on the Silabs website for their 8051 based processors which seem to use exactly the same TWI/I2C interface hardware as Atmel. Since the example is in C you can port it pretty much directly with some name changes.

I've done it the other way round when moving a project from a Silabs part to an Atmel (my own code I hasten to add NOT the Silabs code).

Michael Kellett

Interesting. I must have missed out on this TWI thingy ! What is it ?

Graham

its the dreaded firrips I2C protocol.

OT just been looking at the Grace design 802 remote mic amp, they use I2C over a 1000 foot run, seems dumb to me

martin

I'd guess "two wire interface" (prolly I2C by another name to get around Philips licencing/licensing issues).

Best regards, Spehro Pefhany

In message , dated Wed, 6 Sep 2006, martin griffith writes

That dates you! That 'firrips' ad was run in 1978, I think.

-- OOO - Own Opinions Only. Try

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Advertising works, Havent bought anything with a philips label since

martin

as

with

to

thank u Michael... but i couldnt find the example u was talking about... couldnt find no example with TWI/I2C interface...can u give me link??

thanks a lot

Daniele

Oh ! No problem there then. I have my own I2C routines ( not for master slave admittedly but I dare say that could be fixed ).

If it works ! One of the nice things about I2C is that you can run it at ony old speed. Doesn't mind being interrupted either.

Graham

What *exactly* is it you want ?

Graham

about...

Hello Graham..

I should need the code for the master device and the code for the slave device... but in my case the master and the slave are 2 AVR-AT90CAN128.

I have those 2 devices and want realize a comunications between them using TWI.

Thanks a lot

Daniele

Why does it need to be I2C then ?

Don't they have serial ports ?

Graham

Hello,

The Silabs website is

You will need to register and then search the tech library for SMB (they call I2C SMBus). You'll get a few hits but you need to look at the app note.

Michael Kellett

link??

slave

AVR-AT90CAN128.

using

sure, they have serial ports but i need to use TWI

Will the master always be the master and the slave always the slave?

If so, code is available either from atmel website or a number of other sites, just google. It may not be for exactly your model of AVR, but adapting the code should be easy enough.

SioL

yes

So look for the code out there, it exists. Google is your friend. Avrfreaks etc etc

SioL

ok I'll post some code... look if it could be ok

Master.c

#include #include #include

int TWI_Master_Transmitter(uint8_t data, uint8_t address); void TWI_init(void); void TWI_Master_Transmitter_Error(void);

int main(void) { DDRA=0xFF; PORTA=0xFF; TWI_init(); int a; a=TWI_Master_Transmitter(0xAA,0xE0); if(a!=0) PORTA=a; }

void TWI_init(void) { #define SCL_CLOCK 100000L #define F_CPU 8000000UL

/* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */

TWSR = 0; /* no prescaler */ TWBR = ((F_CPU/SCL_CLOCK)-16)/2; /* must be > 10 for stable operation */ TWCR=(0