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Author Topic: FT932X I2C High speed Mode not working  (Read 1271 times)


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FT932X I2C High speed Mode not working
« on: November 11, 2019, 05:56:43 AM »

Hi Team,
We are performing I2C operation using FT932x for one of our applications. The datasheet mentions that FT930/1/2/3 it will support all I2C modes of operation including the 3.4Mbps mode.

We are facing an issue in our application: We are NOT able to operate the I2C module in FT932x in Fast, Fast plus and High speed modes.
Below is a snapshot of our code (which is similar to the example code provided in the FTDI website) :-
We have shown below the outputs of the I2C CLK at different modes.

Case 1 :-   
Mode : Normal mode

Speed :- 100kbps

usage in the code :-

i2cm_init (I2CM_NORMAL_SPEED, 100000)

Programmed frequency  100kbps and we are able to observe 104kHz in the Oscilloscope.

Case 2 :-
Mode :  Fast mode
Speed :  200kbps
usage in the code :-
i2cm_init (I2CM_FAST_SPEED,  200000)

Programming frequency is 200kbps but we only observe 147kHz on the oscilloscope.

Case 3 :-
Mode :  Fast plus mode
Speed :  400kbps

usage in the code :-
i2cm_init (I2CM_FAST_PLUS_SPEED,  400000)

programming frequency is 400kbps but we only observe 294 kHz on the oscilloscope.

We use a pull-up resistor of 1k ohm on SCL and SDA for all the above tests. As you could see the normal mode (100kHz) works as expected. What could be the issue with the higher speed modes?

Also, we are referring FT930x datasheet v2.1  and it does not have any errata information. We would highly appreciate any input/help from you to get the I2C high-speed modes working.
Thanks and regards,

FTDI Community

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Re: FT932X I2C High speed Mode not working
« Reply #1 on: November 12, 2019, 04:45:41 PM »


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