[Gta04-owner] BMP085 driver in Linux 3.12.0 (Issue #487)

Benjamin Deering ben_deering at swissmail.org
Fri Nov 8 23:59:59 CET 2013


On 11/08/2013 05:00 PM, Dr. H. Nikolaus Schaller wrote:
> Hi,
> I have seen sometimes wrong values from the BMP085 sensor, but in most times they are ok [1].
>
> It may look like this:
>
> root at gta04:~# while true; do echo $(cat
> /sys/bus/i2c/devices/2-0077/pressure0_input
> /sys/bus/i2c/devices/2-0077/temp0_input); sleep 0.5; done
> 94294 393
> 94299 393
> 94293 393
> 94292 393
> 94289 393
> 94293 642
> 100710 393
> 94293 642
> 100710 642
> 100707 393
> 94296 642
> 100711 393
> 94292 393
> 94285 642
> 100701 393
>

Yes, I have seen that.  I should have posted my findings to the list a 
while ago.

Last year (maybe longer ago) I protected the i2c access with a mutex and 
noticed that I still had to increase BMP085_TEMP_CONVERSION_TIME from 
5ms from the datasheet to 8ms to make it work.

In my 3.12 build (maybe 3.11?) it stopped working again.  I set  
BMP085_TEMP_CONVERSION_TIME to 18ms (a made up number) so my barometer 
program (http://www.jeepingben.net/barom/) would work.  I assumed that 
just increasing the timeout was not a good solution so I stayed quiet 
hoping to have time to find a better solution later.

If increasing the delay to make it work will be accepted upstream, then 
I say commit it and call the issue solved.

Ben


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