K64F I2C ACK

[mayawatanabe]

Hello Experts,

I downloaded the K64 sample code for tower board (Kinetis_K64_SC_INIT) from the web site and just changed the slave address to 0x00. And I just pulled up the I2C1 line, PTC10 and PTC11. There is no I2C device. However I saw some "Ack"s (Please refer the attached picture)... Is it normal? or any register setting would be wrong?? I added ODE=1 code into the sample code but there is no change..

I'm using a FRDM-K64F(revB, sch revD1), not tower board. But I thought the sample code would work on FRDM-K64F as well...

Best Regards,

Maya

[Hui_Ma · Accepted solution]

Hi Maya,

When you set the slave address to 0x00, which in fact send a START BYTE.

Please check below picture about I2C first byte definition:

In this case, there with below start procedure:

From I2C bus specification, An acknowledge-related clock pulse is generated after the START byte.

This is present only to conform with the byte handling format used on the bus. No device is allowed to acknowledge the START byte.

So you observe signal is normal.

More detailed info, please check with I2C bus specification page 17.

Wish it helps.

Have a great day,
best regards,

Ma Hui

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