topic Re: Kinetis MCU I2C questions in Kinetis Microcontrollers

Kinetis MCU I2C questions

lucas_zhou — Thu, 11 Oct 2012 03:32:13 GMT

Hi all，

I have a question.

In the Reference manual IIC chapter : The interface is designed to operate up to 100 kbit/s with maximum bus loading and timing.

Does the Kinetis MCU support IIC in the fast mode ?

Thanks!!

Re: Kinetis MCU I2C questions

JimDon — Thu, 11 Oct 2012 14:07:27 GMT

This does not mean

that 100 k is then maximum clock rate. It means that at maximum loading, the clock and data signals will not be usable due to capacitance Loading.

Re: Kinetis MCU I2C questions

carlos_neri — Thu, 11 Oct 2012 16:33:10 GMT

As Jim commented, 100Kbps is the maximum data rate when the bus is at its maximum capacitance load (400pF). If you do not have that amount of capacitance load, the I2C can achieve fast mode (400kbps).

Re: Kinetis MCU I2C questions

JimDon — Thu, 11 Oct 2012 17:48:00 GMT

On other Freescale chips, under ideal conditions I have run I2C at 1.2Mhz just as a test (I have not had a chance to test this one yet).

Note that this is really an overall specification of the I2C bus, not so much the part itself. Also a lower pull up helps for faster speeds.

Re: Kinetis MCU I2C questions

Sirius — Thu, 11 Oct 2012 19:48:27 GMT

Have a look at the I²C specification and manual of NXP:

http://www.nxp.com/documents/user_manual/UM10204.pdf

On page 55 there are easy formulas & charts to determine pull-up values to meet the rise time requirements. Alternatively, take a look at the timing specs themselves in chapter 6.

Re: Kinetis MCU I2C questions

lucas_zhou — Fri, 12 Oct 2012 01:24:50 GMT

Thanks for your help.

I think I get it!!

Re: Kinetis MCU I2C questions

lucas_zhou — Fri, 12 Oct 2012 01:26:18 GMT

Thank you !

It's very useful for me .

Re: Kinetis MCU I2C questions

lucas_zhou — Fri, 12 Oct 2012 01:27:42 GMT

Thank you !!

I get it. I will try it on my board.