[Gta04-owner] Using BMP085

[Benjamin Deering]

I did some work with temperature sensing on GTA02 for my ski wax chooser 
program.  I tried BMP085 mounted outside of the middle part of the case 
and still did not get good readings.  A later experiment showed that a 
lot of heat could transfer through the wires to affect the readings.  I 
ended up installing an MLX90614 infrared temperature sensor.  That works 
well.

Pictures of BMP085 install, BMP085 test, and MLX90614 install:
http://www.jeepingben.net/index.php?level=album&id=24
http://www.jeepingben.net/index.php?level=album&id=26

Ben

On 05/29/2012 05:55 AM, Denis Shulyaka wrote:
> 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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