[Gta04-owner] Using BMP085
Dr. H. Nikolaus Schaller
hns at goldelico.com
Tue May 29 13:25:32 CEST 2012
Am 29.05.2012 um 13:16 schrieb 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.
Yes, the MLX90614 is a chip like what I think we should add to a future GTA04
release for doing reliable outside temperature measurements.
> Pictures of BMP085 install, BMP085 test, and MLX90614 install:
> On 05/29/2012 05:55 AM, Denis Shulyaka wrote:
>> 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*"
>>>>> gta04:~# cat /sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0077/pressure0_input
>>>> I've been looking now at temperature too
>>>> I'm getting 33 degrees C , 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
>>>> 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.
>>>>  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`.
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