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Using i2c — Parallax Forums

Using i2c

Samuel43Samuel43 Posts: 1
in General Discussion
Hi,
I am new to using propeller chips (P8X32A-Q44) and was wondering if it is necessary to to have pull-up resistors on the SCL and SDA lines when interfacing to an external eeprom?

Thanks

Comments

  • jmgjmg Posts: 15,173
    Samuel43 wrote: »
    I am new to using propeller chips (P8X32A-Q44) and was wondering if it is necessary to to have pull-up resistors on the SCL and SDA lines when interfacing to an external eeprom?
    There are no pullups in P8X32A, so you need at least a pull-up on SDA.
    If there is no clock-stretching in your slaves, SCL can be CMOS drive, so does not require a pull-up.

  • Mike GreenMike Green Posts: 23,101
    If you don't use a pull-up on SCL, make sure your I2C I/O routines are written to handle that case. Basic_I2C_Driver (in the OBEX) can do this although it's written in Spin and is relatively slow.
  • Cluso99Cluso99 Posts: 18,069
    The recommendation is pullups on both.
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