Bob,
That's very helpful.
The i2c support was done remotely -- Jan Kandziora's group was instrumental.
That means it works, but was never tuned.
In particular, the i2c has a variable delay in response for different
functions. The original code used a polling loop to wait for a response.
That seemed a little unfirnedly for a multithreading multitasking program
like owfs, so I have a shorter loop -- minimum+10%, average, maximum+10%. I
suspect that we are either too conservative, or are just missing some waits.
It should be possible to test small changes and improve our delays. Even
better would be auto tuning, where the delays are adjusted as the program
proceeds, compensating for the hardware and clock speed.
Of course, it is also possible that we have some inefficient implementation
-- again, the only testing was that is worked.
Paul Alfille
On 2/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
Paul, my apologies for the delay in responding to your question - mail
server
crash.
Regarding statistics, all the error files in the error directory are
"0". The
error files in the bus directory are also "0". I added tracing to the
i2c-dev module and there appears to be quite a bit of I2C_SMBUS read/write
activity when fetching a channel value. So either some piece of data is
being read or re-read multiple times (without error condition). I will
start tracing through the ow_2450 and ow_ds2482 code.
Do you sense I may have a problem here?
regards,
Bob
On 2/14/07 Paul wrote:
> Any errors seen in the "statistics"?
[Original query]
>> I have a board with 2 DS2450 a/d, 1 DS2431 eeprom and a DS2482 as the
bus
>> master. The host processor is a 500 Mhz Geode running Linux. I've
noticed
that
>> there is quite a bit of latency when doing an "ls" on the 1 wire mount
point
or
>> reading any channel of either 2450. For example, reading a 2450
channel can
take from 8 - 15 seconds. Once the >> value is in cache, it pops right
up.
There is a bit of latency with my smbus smartbattery and temperature
devices
but >> its no where near the OW delay.
>> I've read the OWFS Cache page so I understand reading data will be
"relatively slow". That being said, is the delay >> I'm seeing typical
of the
OWFS? I'm just trying to rule out a problem with my hardware or elsewhere.
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