Considerations for using GPIO as I2C

[hyjung]

Dear All.

I am trying to implement I2C of PCA9955B using GPIO with 9S12P128-48pin.
Currently the clock of 9S12P128 uses 12MHz and I want to use 560kHz for I2C communication with GPIO.
Are there any considerations to implement and use it?

Thanks.

[lama]

Hi,

Primary AppNote was created for S08 family devices> https://www.nxp.com/docs/en/application-note/AN3317.pdf 

(IIC Master on the MC9RS08KA2)

Then for a S12 family, search for it in>  https://community.nxp.com/docs/DOC-341377 

(Emulating I2C Master Mode In the S12/S12Z Family)

I believe it will help.

best regards,

Ladislav

[hyjung]

Thank you for your reply.

The application note implements the I2C clock at 108 kHz or 160 kHz.
In addition, does it matter if I2C clocks(560kHz) are higher than the application note?

Thanks.

[lama]

Hi,

The I2C clock is up to you. You have to mainly think about frequency of interrupts of the timer - how it influences other processes. There is no problem with the pin HW. It is the same pin as in the case of real IC mode. So the only issue I see in the processing times and their influence on other processes and/or priority of processes to do not lose data. Bate these consideration must be done by you on the basis of your expectations and program structure.

Best regards,

Ladislav

[hyjung]

Thank you for your reply.

The application note implements the I2C clock at 108 kHz or 160 kHz.
In addition, does it matter if I2C clocks(560kHz) are higher than the application note?

Thanks.