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[Bug 1001397] I2C driver for Kinetis microcontrollers
- From: bugzilla-daemon at bugs dot ecos dot sourceware dot org
- To: ecos-bugs at ecos dot sourceware dot org
- Date: Wed, 24 Apr 2013 09:07:59 +0000
- Subject: [Bug 1001397] I2C driver for Kinetis microcontrollers
- Auto-submitted: auto-generated
- References: <bug-1001397-13 at http dot bugs dot ecos dot sourceware dot org/>
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--- Comment #60 from Ilija Kocho <firstname.lastname@example.org> ---
Created attachment 2206
I2C driver print out actual frequency when trace enabled. Increment to
(In reply to comment #59)
> After setting CPU clock to 100Khz:
> Freq Mode Meas
> 100Khz Std 98Khz
> 100Khz Agr 111Khz
> 400Khz Std 363Khz
> 400Khz Agr 416Khz
Thank you for the measurements.
> From an application point of view, this is a little problematic, in that:
> - When you set the goal and value, you don't get feedback in the
> configuration that tells you what the result will be. You have to get a
> scope and measure it.
> - If you want to make it more accurate, you have to either guess the correct
> CPU clock, or reverse engineer the algorithm to calculate the required clock
> One solution might be to have the configuration calculate the proper CPU
> clock so you can then manually change the clock to get a better result.
It would be good to have this convenience in CDL but it requires some Tcl
programming, which requires some time...
The second best is to enable some printout at run-time. The attached
incremental patch enables printout of actual I2C clock frequency and period
when trace is enabled.
Note: The printouts that I got are pretty close to what you have measured for
100kHz, but there is a large discrepancy for 400kHz. Can you please and repeat
measurements and check the printouts?
> I am ok with committing the solution as is because I can figure it out for
> 100 and 400 and will have the only answers I need. I think it is just a
> question of how much you want to help the application programmer.
If you are happy with proposed patch and there aren't objections, I would
proceed with commit.
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