Am Mittwoch, 5. September 2007 19:43 schrieb Geert Vancompernolle:
> Did you use a scope already to look to the signals?
not yet. But I want to do that on the weekend.
> You could indeed change the speed of the I2C driver using an option,
> but then you will sacrifice the speed of I2C for one or two devices
> that are too slow: all other devices get a penalty because of a few
> and that would be a pity...
true.
> What I find strange: if the device cannot follow, it should stretch
> the clock such that the next byte cannot be sent until the device has
> processed the data.
I just found that clock stretching is an option on some PICs and can be
enabled/disabled in the program.
("DEFINE I2C_HOLD 1" in Basic)
So this might just be a bug in the firmware of the SD20...
I will check with the scope if it does or not.
> In stead of changing the delay statically, I could add an option in
> the IOCTL routine that, for instance, halves the speed. Then you
> could change the speed to half for those slow devices and revert back
> to full speed once the communication is done.
> That would be better then changing the speed to half "forever"...
I like this idea! It also has the advantage that you can change the speed for
buggy/slow devices without recompiling the kernel and reflashing.
> I will see how I can change this, but I'm now busy writing a C++ I2C
> HAL classes on top of the direct IOCTL calls. Having such additional
> option is not a lot of work, so I can take this into account...
That would be great!
-Cornelius
--
Cornelius Claussen
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