IWR6843: I2C master frequency inaccurate

Benjamin Becker

Intellectual 305 points

Part Number: IWR6843
Other Parts Discussed in Thread: AWR1443

Hello,

we have again an issue with the I2C clock frequency. This time on the IWR6843.

We use SDK 3.3.03 with target frequency of 400 kHz.

The IWR6843 outputs only 380kHz, while AWR1443 with the same code and same SDK driver code outputs exactly 400kHz.

By the way, this is exactly the inverted issue we once had with AWR1443 (see issue "AWR1443: I2C master frequency inaccurate"). It had been fixed by modifying a "magical number" in the SDK I2C driver code.

Following the reference manual swru522d, which was updated in the meantime, the formulas are correct. But the device does not behave according to the spec.

Please provide a reliable explanation.

Regards, Benjamin

over 5 years ago

0 Benjamin Becker over 5 years ago

Intellectual 305 points

It seems that this phenomenon is sporadic. Sometimes the I2C works with 380k, sometimes 400k. OS tasks are accurate in both scenarios -> It seems not to be a VCLK issue.

I cannot absolutely exclude an issue with compilation of the SDK. But we rebuilt our software on 2 independent machines and got identical binaries.

What I especially observed:

- I modified the calculation of ICCLKL / H in the i2c_reg into the old code with subtraction of 6 and ran this in the debugger Then I got 444kHz.

- I modified it back to 5, and reached exactly 400kHz

- I reflashed our old release into the QSPI FLASH. When I start it up with the JTAG cable disconnected, it shows 380 kHz

- I switched off the target, connected the JTAG cable, switched on again and re-connected with CCS, without flashing anything. Then it ran with 400 kHz again.

I will check tomorrow if I can compare the I2C driver part of the release with the code I recently compiled, to check whether this is a linker issue.

0 Charles Oladimeji over 5 years ago in reply to Benjamin Becker

TI__Mastermind 33805 points

Hi,

I will check with the SDK team and get back to you.

BR,

Charles O

0 Charles Oladimeji over 5 years ago in reply to Charles Oladimeji

TI__Mastermind 33805 points

Hi,

Can you please provide a dump of the I2C registers for both scenerios?

BR,

Charles O

0 Benjamin Becker over 5 years ago in reply to Charles Oladimeji

Intellectual 305 points

Hello Charles,

Unfortunately not yet. The 380 kHz phenomen happened only with release builds and no debugger connected so far.

I will try it with a special release that reads out the registers when I find the time.

Regards, Benjamin

0 Charles Oladimeji over 5 years ago in reply to Benjamin Becker

TI__Mastermind 33805 points

Hi,

Please let me know when you do.

BR,

Charles O

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IWR6843: I2C master frequency inaccurate