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I2C EEPROM wiring — Parallax Forums

I2C EEPROM wiring

RsadeikaRsadeika Posts: 3,837
edited 2006-11-21 16:35 in Propeller 1
I have been staring at the schematic for the eeprom wiring on my propeller kit, and I guess I am looking for an explanation as to why this circuit only has a 10K pullup on the sda line. Everything that I have seen usually recomends 4.7K pullups on both the sda and scl lines, just trying to clear up the confusion in my head.

I am also thinking of creating an I2C hub, should I modify the existing setup on p28 and p29, put in 4.7K pullups, or pick two other pins and add the 4.7K pullups there, or do I really need 4.7K pullups at all.

Thanks

Ray

Comments

  • JavalinJavalin Posts: 892
    edited 2006-11-21 16:35
    You can, and Parallax has, get away with a pull-up on the SDA line only - if you activity drive SCL high and low.

    You're correct that usually these are both pulled high via 4.7k's.

    The other issue that this causes is that the reboot/reset doesn't work on the demo board (I believe - as I haven't got one) as the EEPROM can hold the SDA and hence the RSET line high.

    My i2cObject in the propeller library works both ways, when you do an Init you set the "driveLines" parameter to TRUE

    James
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