[U-Boot-Users] I2C @ MPC8343

[Martin Krause]

Hi Andre,

u-boot-users-bounces at lists.sourceforge.net wrote on :
> All,
> 
> in my current system the I2C bus is not working properly on a MPC8343
> in 
> u-boot v1.3.2.
> 
> i2c board config includes :
> 
> #define CONFIG_HARD_I2C
> #undef CONFIG_SOFT_I2C
> #define CONFIG_FSL_I2C
> #define CONFIG_I2C_MULTI_BUS
> #define CONFIG_I2C_CMD_TREE
> #define CFG_I2C_OFFSET          0x3000
> #define CFG_I2C2_OFFSET         0x3100
> #define CFG_I2C_SPEED           100000
> #define CFG_I2C_SLAVE           0x7F
> 
> 
> chip probing works fine.
> 
> mvBL-M7> i2c probe
> Valid chip addresses: 30 48 50 68
> 
> reading the Chips gives all "ff"
> 
> mvBL-M7> i2c md 50 0 10

Uh, it seems I lag behind in U-Boot evolution. I know this
"i2c md" command as "imd"?

> 0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff   
> ................ 

Devices with address 50 normally are EEPROMs. If this device is an
EEPROM, are you sure it contains data other than 0xff?

The number of address bytes a device needs is varying. Your could
look up the correct address length in the datasheet of your device,
or try it manually:

imd 50.0 0 10
imd 50.1 0 10
imd 50.2 0 10

One of this should work.

> Observing the I2C bus wires show that everything _works excellent_ :
> 100kHz speed as well as all data seems ok - but u-boot shows "ff".
> 
> BTW:  Fetching HRCW from I2C is also working fine.
> 
> After some tries (i2c md ..) the bus hangs and no more transactions
> can 
> be seen on the bus.

One reason for a hanging bus could be a lost clock pulse. This could
happen, if the low->high rise time of the bus signal is longer than
the clock pulse width. For testing you could try a lower bus clock 
(10 kHz for example).

Best Regards,
Martin Krause
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