[Gta04-owner] Using BMP085

[Denis Shulyaka]

Hi,

2012/5/29 Dr. H. Nikolaus Schaller <hns at goldelico.com>:
> Hi Neil,
>
> Am 29.05.2012 um 11:18 schrieb Neil Jerram:
>
>> Neil Jerram <neil at ossau.homelinux.net> writes:
>>
>>> Hooray, it works, thank you:
>>>
>>> gta04:~# echo bmp085 0x77 > /sys/bus/i2c/devices/i2c-2/new_device
>>> gta04:~# find /sys -name "*pressure*"
>>> /sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0077/pressure0_input
>>> gta04:~# cat /sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0077/pressure0_input
>>> 92192
>>
>> I've been looking now at temperature too
>> (/sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0077/temp0_input).
>>
>> I'm getting 33 degrees C [1], although the actual temperature in my
>> house is only 16 degrees C.  Is that because the temperature reported is
>> intentionally that *inside* the GTA04, and hence reasonably higher than
>> ambient?  If so, is 33 degrees a reasonable temperature to be measuring
>
> Yes.
>
>> inside the GTA04?
>
> Yes. It can go up to 45-50 degrees if the CPU is running at full power.
> The BMP085 is mounted directly near the CPU and the PCB also
> distributes the heat of other high-power components (WLAN).

What about temperature sensors inside gyro and accelerometer? Are the
chips mounted farther from the CPU?

> The temp measurements of the BMP085 are done for compensating the
> pressure readings and are not intended to indicate the correct outside temp.
>
> Maybe, we can try to use a thermopile sensor in some future device.
>
>>
>> [1] To be precise, I mean that ((VALUE + 5) / 10) = 33, where VALUE is
>> `cat /sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0077/temp0_input`.
>>
>> Regards,
>>        Neil
>>
>
> BR,
> Nikolaus
>
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