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198Re: I2C delay doesn't work on OKI675001

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  • ChrisH
    Mar 19 6:23 PM
      A few years back, one of the I2C slave devices we needed to
      support was a power supply which required I2C clock stretching
      (pulling the I2C SCL line low) similar to what you are experiencing.
      We were using the OKI675003, and if I recall correctly, the I2C
      master in this part does not support clock stretching. It would
      do exactly as you are observing -- continue clocking data even though
      the slave is holding down SCL.

      I implemented a bit-bang I2C master which used the same GPIOs
      as the OKI master. That worked quite well. In fact, that
      code is now being used in a new design with the OKI675003
      which supports several I2C buses directly attached to OKI
      GPIOs. I suggest you search the net as there are most likely
      a good number of sample bit-bang I2C masters out there.

      -Chris Hooper


      --- In OKI-ARM-mcus@yahoogroups.com, "flaretom" <thorn@...> wrote:
      >
      > Hi Everyone!
      > I'm having some trouble with the 675001 regarding the i2c-hardware in the MCU.
      > The Oki-i2c hardware is connected to an Atmel-AVR, which is working as i2c-slave. Sometimes the AVR is not as fast as the oki-mcu and pulls the i2c-scl line low after its acknowledge pulse(i2c-delay). Unfortunately the oki-mcu does not detect this and continues to send its data on the i2c-sda line. Of curse this ruins the whole communication, and to make things worse the state can't be left by software means (reinitializing the i2c hardware in the oki-mcu).
      > Does anybody observe a similar behavior and hopefully has a workaround?
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