[Gta04-owner] GTA04 thermal imaging

Dr. H. Nikolaus Schaller hns at goldelico.com
Wed Feb 15 08:08:29 CET 2012


Am 15.02.2012 um 03:01 schrieb NeilBrown:

> On Tue, 14 Feb 2012 20:43:36 +0100 Christoph Mair <christoph.mair at gmail.com>
> wrote:
> 
>> Hello,
>> 
>> last weekend I could capture a few thermal images from my phoenux. I
>> have not reviewed them in great detail yet, mostly due to lack of
>> time. If you want to do you own guesswork, here are the pictures:
>> http://www.chonyota.net/gta04/infrared/
>> 
>> The first directory (20120212) contains images captured at different
>> software states. Mostly running (booting up) and a few in suspend. You
>> can easily identify the suspended state by looking for images with low
>> overall heat dissipation and just the RS232 interface consuming lots
>> of current (its the chip in the top right corner). I also did a shot
>> without serial connection (not so easy to identify because I only
>> detached the cable from the USB-RS232 converter)
>> 
>> The second directory (20120213) contains a picture which was made
>> while suspended on the evening of sunday. The next pictures were made
>> on monday morning while waking the device from standby by connecting
>> the serial line.
>> 
>> In general, look at the timestamp, then you might figure out why the
>> head dissipation could have changed so much (or why not).
>> 
>> Till now I did not find some serious issues during suspend. I just
>> observed that even if my WiFi was switched off, its level shifter uses
>> some current with a periodically recurring pattern.

Maybe, some kernel component is polling the MMC2 interface for
hot-insertion (there is no Card-Detect mechanism). This means switching
on the SDIO clock, trying to communicate, retrying and failing...

>> 
>> If you have questions or comments, please write them to this list. If
>> you have suggestions or maybe a ready-to-execute thermal test plan,
>> please let me know. I'll try to rent the camera once again. Its just
>> too much fun to play with it, unfortunately I was quite busy during
>> the last weekend and didn't have time to use it a lot. I'm planning to
>> capture some live videos if I manage to get a S-Video framegrabber in
>> time. That will be fun :)
> 
> Wow! Thanks for doing this.  It is interesting that the internal usb
> interface and the RS-232 interface stand out so much.  And neat to see

Well, USB 2.0 is a RF system (480 MBit/s)...

> different parts of the WIFI/BT chip heating up at different times.
> 
> Does just unplugging the RS-232 cable reduce power drain in suspend?  That
> would be good.

I think one of Christoph's images shows that. And the data sheet says:

POWERDOWN:	1 - 10 uA
No Load:		0.3 - 1 mA (this may be less than the IrDA receiver)

There is no specification about the load currents. But they are multiplied
since the charge pump has not the best efficiency.
So I would assume 5 mA for each mA at the outputs.

Anyways this means that if there is no RS232 cable plugged in (which is
the normal operation case for the plain user), there should not be more
than 1 mA i.e. 3 mW. This can't be the reason why suspend does not
work well enough.

Other ideas for suspend:
* is the USB3322 powered down (GPIO 174 = 0)?
* is the GPS module switched of (or does it switch on unintentionally by power-down)?
* does the video amplifier OPA362 remain disabled (GPIO23 = 0)?

Nikolaus


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