The Strange Case of the Hardware problem that wasn't

During my bout of Raspberry Pi hackery yesterday, I realised that, currently lacking an HDMI to VGA converter, the only way I was likely to get anything displayed was by connecting the composite video out to something... and immediately I dug out my little Dell M109S LED projector.

Which, as it turns out, did manage, for one brief moment, to lock onto the Pi's output before giving up.... but that's life. Incidentally,  I had already had some problems getting the Pi to boot from various SD cards before I figured out the magic incantation which, to save you trouble is:-

1. Give up on the useless Win32 disk imager they recommend. It doesn't work on most laptops, you can't view the destination drives. Flashnul, the alternative, is a much better option. But I found that it was important to zero out the SD cards before use. Otherwise only one of three cards actually booted. To do this, use the -F option in flashnul. Also it's important to use the physical drive number - typically 1 - and not the logical drive name e.g F:, for all operations. BE CAREFUL!. This is a semi-automatic weapon with, to be sure, a safety catch but pointing it at the wrong drive could be catastrophic.

2. Then use the -L option to load the image and copy it to the SD card. Voila. Zeroing out seems to fix a lot of the supposed incompatibilities the Pi has with various SD cards. I have no idea why, it just worked for me.

Note to the Raspbian crew.(BTW I love the name of the distro. It still makes me chuckle. Based on Wheezy, too!. Ah, the joy of open-source names where no marketing droids tread!). Could you give us a variant distribution where the IP address is fixed e.g say 192.168.1.200 or something and VNC server is already installed. Then we could just hook up a crossover internet cable and VNC into the thing. Since I suspect 99% of purchasers already have a perfectly good PC, this is much cheaper and easier than purchasing adaptors and fiddling around with keyboards and mice, just to set this up once and then connect using VNC from then on. (which is what I intend to do, but I'm stuck by the chicken and egg scenario at present, unless I care to fire up a Linux VM and hack around with the SD card.)

But I digress. Having got the Pi to boot, and very briefly seen its initial startup menu, I realized the projector just wasn't going to sync up reliably. I turned it off and then on again just for one final check and - zap - the white background had turned cyan. Hmmmm....

Cycling power didn't help. Nor did a factory reset or any amount of fiddling with the RGB levels in the setup menu. It looked like the red LED had partially failed. Not completely - there was some red in the test patterns, but partially. So I pulled the lid off in the vain hope that reseating a cable might help, managing in the process to separate the cable retaining clip from the connector that attaches the keypad, and then spent a good ten minutes fiddling around under a strong magnifying glass trying to reattach the clip, which is the size of a sliver of fingernail, back to the connector. I have no idea how these modern gadgets are assembled. When one finger dwarfs a whole cable and connector, and resistors and capacitors are reduced to grains of sand, it really does feel at times like you're a huge and clumsy giant, something out of Gulliver's Travels.

Of course, all this proved to be pointless, but when something's long out of warranty, what is there to lose. Sadly, I added it to the long list of gadgets that had passed away in the course of service, over the years. Of course, needless to say, no such thing as a service manual exists - at least in the public domain. And I could already hear the sarcastic laughter over the phone if I were to ring Dell for out-of-warranty service.

I turned it back on and off. It was still as blue as I was. But, oddly, on power off the screen flashed momentarily white. That seemed odd. If the red LED had really had a partial failure, how was the projector managing that feat?. So I took a closer look. With no input source selected, adjusting R,G and B values had no effect at all on the screen. That seemed unusual. And where were all the other options I vaguely recalled seeing, about 'degamma' (whatever that is) and contrast and brightness.

I reconnected a VGA source. Now the extra controls were visible and had some - but not much - effect on the screen. On a whim, I wound down the blue and green settings to zero and then wound the red up to 100. It was feeble but the screen was definitely pink. Then I cycled the power again.

This time, the red seemed much brighter. To my astonishment, setting all levels back to 50 restored my normal white screen. This survived several more power cycles and seems to be back to normal now.

This is certainly one of the odder software bugs I've ever seen. Somehow the projector lost control of the LED levels, but only partially. I've never seen something that looked more like a hardware problem than this. Ah well. If you have one of these projectors and have a similar problem, I hope this helps you, before you give up on it. Dell probably know about this but if they do, there's nothing I could find on the net.