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open-phd + indi server (qhy5) on a Raspberry PI


Gonzo

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At least one of the problems with the PWC driver is that i was hideously non-compliant with V4L2 and not many people seemed interested in fixing it. Perhaps that has changed. If I had the time I'd have given it a go myself.

James

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I don't I'm afraid, though it may be worth searching through archives of the V4L mailing lists if you can find them.

The problem came to my notice because I had a SheevaPlug that I wanted to use to drive an all-sky camera. Initially I couldn't get either the SPC900 or the XBox Live cameras to work, though the latter was close. I ended up doing a bit of tweaking in the UVC driver code for the Xbox camera and got it working, but discovered that it's not really sensitive enough for a night-time all-sky camera.

I then looked at the PWC driver for the SPC900 and discovered that it just doesn't implement an awful lot of the V4L2 interface and that to get anything working the application has to have a lot of knowledge about the camera and perhaps even talk to the USB layer directly. In theory the likes of wxAstroCapture and qastrocam-g2 should be able to talk to any V4L2-compliant camera driver and capture from them, but in fact I think they both have a lot of code built-in to drive the specific cameras they support.

There's a bit of "history" with the PWC driver, too. IIRC the original author used some code that had been licensed to him by Philips and that licence somehow got withdrawn. Someone else reverse-engineered enough to get it working and there was a bit of a strop over the whole issue. These days I'm not sure there's an official maintainer for it at all. I guess that's hardly surprising given that most people who want just a webcam won't have the SPC900 any more. It only really seems to be people into astro-imaging who are still interested in it.

James

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Well, I am on the verge of giving up with the Pi. Too many errors, the Pi hardware is just not tolerant enough of USB peripherals. USB hub getting reset after a few minutes, the pwc module only works half the time, no controls seem to do what they are supposed to, it's a mess. All I want is a module that would let me do 5fps, 640x480, I420: how hard can it be?

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I don't have a Pi (yet - may be tempted to get a version 2) but when I first read about it I wondered if it could be used for astronomy purposes. Could the problems being experienced be result of using Raspbian as opposed to the other distros available?

I have this crazy(?) vision of a Pi for guiding, one for image acquisition (storing onto a suitably sized USB key or even a hard drive) and possibly one for mount control, each controlled remotely via VNC or similar. You could house them all in a power box (along with leisure battery and connections for dew hearts etc, and a small ethernet hub/switch) :D

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I have been able to get the SPC900 to work on my PI, using motion. Now the major downside is that the only resolution that works is 176x144 anything higher and motion will not work. It seems that this webcam is not fully compatible with the PI.

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There is something in the v4l drivers that allows you to use a 'compat' module as a wrapper, (I think you use ld or something to load it before running the actual app. that you want to use.)

I think there are probably plenty of cameras that the pi will work with, we just haven't tested them and we desperately want the spc900nc to work. I think one of the issues for the pi is that it's using a kernel that is 'too new' for the pwc drivers, the drivers were better it would appear around 2.6.xx rather than 3.x.x.

I think if enough of us turn up on the raspberry pi forums at the same time asking questions, we might get better support over our driver, the first thing is definitely getting > 160x120 resolution, this could be down to raspberry pi usb issues or it could be down to pwc ioctls being missing. I'm going for a mixture of both.

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Seems I was entirely wrong on the path :D you actually have to install libv4lconvert0 and libv4l-0 (if you 'sudo apt-get install webcam' it will install both as dependencies automatically). you can then find the modules in /usr/lib/arm-linu-gnueabihf/libv4l/. look at this page for instructions:

http://linuxtv.org/downloads/v4l-dvb-apis/libv4l.html#id3156114

in the 'v4l1compat.so wrapper library' section at the bottom of the page.

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After reading more an more posts about the USB on the PI, it appears that this poly fuse is really a pain in the ass. ~The V2 board has been fixed I believe, but if you have a V1 board then bypassing the fuses with a 1ohm resistor does the trick.

Should have known that earlier as I was in town buying my sdcard... doh :(

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