I2C module on MKV31F512XX device fails at 120Mhz

[gokhangunay]

Hi all,

I am playing with I2C module on MKV31F512XX device to controll ssd1306 display.

I could program the device successfully at 8MHZ clock so it is OK at this frequency. But whenever I raise the clock to 120MHZ it fails (after setting baud rate in accordance).  I have attached the oscilloscope outs for both cases. As you can see on the defect case, 9 th clk cycle does not coincide with ACK on SDA.

Do you have any experience with this issue? Have you ever used the I2C port while the MCU is running at 120Mhz?

thanks

[miduo]

Hello,

I would like to know what you mentioned of the "failure". When you "raise the clock to 120MHZ it fails ". It fails to programming the device or the I2C fails to connect with the ssd1306 display? And what IDE and what board you used?

[gokhangunay]

Hi Fang Li,

thanks for the action. The MCU and I2C module are programmed ok and MCU runs well at 120Mhz, but the I2C module on the board behaves weirdly at this frequency (or i did something wrong). I can smoothly connect to ssd1306 at default MCU clock (without ext osc and pll active). However, whenever I activate PLL and set MCU clock to 120MHz (with recommended hsrun mode and and core/bus/flash clk frequencies) and set the baudrate of I2C module in accordance, it fails and does not wait for slave device to send ACK as you can see on the images I previously attached. I use Kinetis design studio and customized board. I also tried the same thing on frdm-kv31 board and got the same results. thanks again.

[miduo]

Hello,

For your customer board, it is hard to find the root without the hardware schematic. Anyway, it is quite straightforward to test with NXP evaluation board, the FRDM-KV31F. What project code have you run with the FRDM-KV31F? And what you mean of the "same result". Any more detailed information appreciated.