[U-Boot-Users] SOFT_I2C on at91rm9200

[Nils N. Gjerdevik <nils.gjerdevik@gmail.com>]

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