LPC804 I2C: Input clock and open drain mode

[olikraus]

Dear Community

I have two questions regarding the LPC804 I2C subsystem

Question 1:

Table 221 (section 15.7.1) of the LPC804 user manual provides some settings for the I2C timing. To me only the row with 12 MHz seems to be useful, other clock input rates are not possible from my perspective, or did I miss something?

Especially one row assumes 30 MHz clock input and two more rows assume 24 MHz clock input to the I2C subsystem.

How can I drive the I2C subsystem with 30 MHz or 24 MHz?

The highest clock selectable via "LPC_SYSCON->I2C0CLKSEL" seems to be 15 MHz.

Question 2:

Do I need to enable open drain mode for the GPIO ports connected to I2C SDA and SCL signals?

Thanks,

Oliver

[ZhangJennie]

Hi Oliver Kraus 

Yes, you are right. Table 221 is the general reference to LPC I2C module.

If you want to use I2C, you must enable IO open drain feature.

Have a great day,
Jun Zhang

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[olikraus]

Thanks, I will activate open drain mode.

Actually my system works with and without open drain mode.

Oliver

[ZhangJennie]

Yes, enable open drain mode please. Thus you can safely get correct data.

Have a great day,
Jun Zhang

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Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
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