[U-Boot-Users] SOFT_I2C on at91rm9200

[Joakim Tjernlund]

On Mon, 2007-06-18 at 15:51 +0200, Nils N. Gjerdevik wrote:
> Joakim Tjernlund wrote:
> > On Mon, 2007-06-18 at 13:39 +0200, Nils Gjerdevik wrote:
> >   
> >> Hi,
> >> I'm trying to store the u-boot environment in an EEPROM (at24c128) on
> >> a custom at91rm9200 based board. This fails when using the included
> >> HARD_I2C driver, and since there are known problems with the I2C
> >> controller on this uC, I'm trying to set up SOFT_I2C instead, without
> >> success so far...
> >> This is what I've put in my config file:
> >>
> >> #define I2C_INIT \
> >> do { \
> >>   *AT91C_PIOA_PER = AT91C_PA25_TWD | AT91C_PA26_TWCK; \
> >>   *AT91C_PIOA_ODR = AT91C_PA25_TWD; \
> >>   *AT91C_PIOA_OER = AT91C_PA26_TWCK; \
> >> }while(0)
> >>
> >> #define I2C_ACTIVE (*AT91C_PIOA_OER = AT91C_PA25_TWD)
> >>
> >> #define I2C_TRISTATE (*AT91C_PIOA_ODR = AT91C_PA25_TWD)
> >>
> >> #define I2C_READ ((*AT91C_PIOA_PDSR & AT91C_PA25_TWD) != 0)
> >>
> >> #define I2C_SDA(bit) \
> >> if(bit) { \
> >>   *AT91C_PIOA_SODR = AT91C_PA25_TWD; \
> >> } else { \
> >>   *AT91C_PIOA_CODR = AT91C_PA25_TWD; \
> >> }
> >>
> >> #define I2C_SCL(bit) \
> >> if(bit) { \
> >>   *AT91C_PIOA_SODR = AT91C_PA26_TWCK; \
> >> } else { \
> >>   *AT91C_PIOA_CODR = AT91C_PA26_TWCK; \
> >> }
> >>
> >> #define I2C_DELAY    udelay(5)
> >>
> >> Can anyone see what's wrong with this code?
> >> I can access the EEPROM without problems in Linux, using the
> >> bit-banging driver, so the board design should be OK. The code above
> >> is(loosely) based on the Linux bit-banging driver.
> >>
> >> Regards,
> >> Nils
> >>     
> >
> > Hi Nils
> > Don't know anything about at91rm9200, but you could
> > test the below patch I sent a few weeks ago. I have tested
> > it now and it works for me.
> >
> > ---
> > I think the README w.r.t I2C_TRISTATE is OK as is(don't change it). I do
> > think the soft i2c driver is broken in several places w.r.t
> > IC2_ACTIVE/I2C_TRISTATE and I2C reset sequence. The below patch is an
> > attempt to fix it, but I havn't tested it.
> >   
> Hi Joakim,
> I'm afraid your patch didn't help. All reads just return 0x00, so I 
> guess it's related to my definitions for the at91rm9200 and not the 
> generic soft_i2c code.
> 
>     Nils

Nils, try changing ACTIVATE and TRISTATE to toggle direction, TRISTATE
should set the pin to input and ACTIVE to output. I think you should
keep my patch while doing so.
If you can use a true open drain output, then ACTIVATE and TRISTATE
should be empty.

 Jocke