I've been tasked with adding I2C slave functionality to a tiny little LPC2101 based board. I'm new to ARM, although I'm quite familiar with other 32 bit processors (PIC32, Blackfin, etc.) I'm using Yagarto.

Anybody know of any simple little examples to help me get started? I'd rather not have to reinvent the wheel. I see that NXP provides some super simple assembly example code in an app note - but I'm hoping there's something a bit more polished out there.

Thanks-

*Brian
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Brian,

On Tue, 2011-03-01 at 21:49 -0600, Brian Schmalz wrote:
> I've been tasked with adding I2C slave functionality to a tiny little
> LPC2101 based board. I'm new to ARM, although I'm quite familiar with
> other 32 bit processors (PIC32, Blackfin, etc.) I'm using Yagarto.
>
> Anybody know of any simple little examples to help me get started?
> I'd rather not have to reinvent the wheel. I see that NXP provides
> some super simple assembly example code in an app note - but I'm
> hoping there's something a bit more polished out there.

For me the best way to get started with i2c was hooking up a pcf8574
to the micro and start writing the master code. This way I could get
the understanding needed on how the i2c bus works and how to write
the i2c interrupt code.
But first off I would like to advice you to get one of these :
http://www.saleae.com/logic/
It works beautifully on Linux ubuntu/debian !
Then there's appnote an10369 from the nxp site.
And do not forget to read the i2c protocol pdf um10204.

First you need to initialize the i2c registers/hardware. Set the scl
frequency to a low value just for debugging. Do not forget about the
aa bit and the IO pin setup.

In the interrupt code you will have a switch/case like this :

void i2c_interrupt_service(void) blahblah
{
switch(i2c0stat)
{
/*
* Miscellaneous state 0x00
*
* Bus error during MST or selected slave modes,
* due to an illegal start or stop condition.
* State 0x00 can also occur when interference
* causes sio1 to enter an undefined state.
*
* Switch to not addressed slave mode.
*/
case 0x00:
....
break;

/*
* MT/MR 0x08
*
* A start condition has been transmitted.
*
* Slave address + write will be transmitted.
*/
case 0x08:
.....
break;

/*
* MT/MR 0x10
*
* A repeated start condition has been transmitted.
*
* Slave address + read will be transmitted;
* or
* Slave address + write will be transmitted.
*/
case 0x10:
....
break;

more case statements.....

}
}

And ofcourse our great friend Google :-)
Search for "i2c bus"; lots of information.

roelof

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