Strange problem with i2c master on FRDM board

[steve_fae]

Trying to see any Master i2c bus activity on the FRDM board.  I actually turned on both i2c ports [just to make sure something didn't happen to one port.

For one port, I used the I2C_LDD method, basically copied straight out of the "typical usage"

And not seeing any activity on either the clock line or data line [which has a 10K pullup resistor to 3v of course]

I used the higher level component just to send one byte on the other i2c port.  .

test:  I2C2_SendChar(0xaa);

goto test;

Problem:  I don't see any activity at all.  The clock lines are non-active.  Any ideas?

[BlackNight]

It is possible to cut off the clock from many peripherals on the KL25Z, known as 'clock gating'. But by default this should not be the case.

I suggest that you try one of my examples (e.g. Accelerometer demo) on GitHub if they work for you.

[steve_fae]

Got i2c working on the FRDM board.  Thanks for your help again Erich. 

[Smiffytech]

Just out of interest, what was your solution?

[steve_fae · Accepted solution]

Well I still don't have i2c fully running but I now have a clock active during Master i2c transmission.  Since I am new to Kinetis programming, I was calling the i2c master transmit from a timer interrupt routine.  Basically I am just data logging for time on.  When I moved the call outside of the interrupt routine I am now able to see the clock.  Interesting to note also is for the eeprom, Microchip only suggests using a pullup on the SDA line.  But for the FRDM board, while communicating with the accelerometer, they use a pullup on both the SDA and SCL lines.  So I added the additional pullup as well. 

[Smiffytech]

Weird about the pull-up on SDA only, unless there is some sort of pull-up in the Microchip part - because the electrical nature of I2C means it HAS to have pull-up resistors on both SDA and SCL. So, if you're doing I2C on pins other than the ones with the pull-ups on the Freedom board, yes, you need those resistors.

[steve_fae]

Hey Erich, I ran your project and probed the signals at the pullup resistors on the FRDM board.  I see activity.  When I try to reconfigure the component and move the signals to any other i2c port pins and add some additional 5K pullups I still don't see any activity. 

There is a bit of a mystery to i2c on this lovely FRDM board.