July 12th, 2016

Fun with the camera (on N900)

Ivaylo Dimitrov got camera to work on N900. Great. Unfortunately... there's works and works.
Working /dev/video* devices does not mean you get useful photos easily. I managed to get flash and autofocus hardware to work... But that still does not mean useful photos.
It seems that http://fcam.garage.maemo.org/fcamera.html is the best way to get the photos. Now... having phone act as a ssh server on local network, with gcc and development tools installed is very convenient... but sometimes you forget that this is not a powerful machine you normally work at.
Oh and BTW... is someone maintaining fcam-dev? Last update in svn is in 2011... I guess I'm maintaining it now...

Auto exposure is quite tricky to do right, and fcam-dev relied on some kernel patches to provide adequate performance. (If someone has pointer to the patch, that would be nice, BTW.) But... people were taking photos before auto exposure was available. And n900 has light sensor, so we can actually use it to bootstrap the auto exposure, making it slightly faster. Seems to work now. I had auto focus working with extremely ugly hacks... but I guess it will be easier to just let user focus manually. The camera is small enough that it should be feasible.

I played with the camera cover, and if you open it in the dark, it starts the flashlight (because that's what you probably want). If you open it with enough light, it will start camera for you. I feel proud.

N900 is a "little" loud in headphones. And it still plays PCM when mixer is set to 0. Weird. But probably topic for another investigation.

Charging (etc) on N900 is still funny. If you poweroff while charging, it will keep charging. That's probably a Linux bug. Charge counter (battery percent) are "kept" even if you replace the battery. Ouch. (So you replace empty battery with full one and still get empty reading. I guess normal people don't have 3 batteries for their phones?) That may be a hardware bug.
You can set charge voltage to more than 4.2V. That will make battery catch fire. I wonder what it is useful for, I guess when you want to have fun on the airplane? /sys/class/power_supply/bq24150a-0/registers is not exactly one value per file. Not sure about mode. model_name is definitely not one value per file.

dx.com 406496 : USB power meter. Seems to work quite well (I compared amper meter with other one, and they agreed +- 10%, so numbers do not look completely useless), and is very useful for debugging power issues. But it seems that USB power supplies often provide about half of their rated current...

Facebook spyware push and unexpected N900 advantages

Dear Facebook. I'm aware that your Facebook lite is only 1MB. It is also dangerous spyware. You try to push it to me every time I attempt to use m.facebook.com. Would not it be nice if you avoided pushing your spyware to phones that can not handle it? Yes, that's right, your spyware requires too new android, so my phone is actually immune from it.
At least N900 seems tu be immune from this problem, you don't even try to push your crap there. Good.