Adding GPIOs To The Raspberry Pi With The Camera Interface


The Raspberry Pi Model B+ was just released, and now everyone who picks one of those up has a few more GPIO pins to play around with. For the millions of people with the two-year-old version of the Pi, we’re still stuck with the same old, same old: 17 GPIOs on the big header, and that’s about it as far as toggling pins goes.

The Broadcom SoC on the Pi has far more GPIO pins than are broken out on the large header, and a few of those go to the CSI camera interface. These GPIOs can be broken out with a few flat cables (Portuguese, Google Translatrix), giving you four more GPIOs, and this technique can also be used with the new, expanded Model B+.

The CSI camera connector has two I²C lines that go directly to the camera, controllable in Linux as GPIO0 and GPIO1. There are two more GPIO connectors on the CSI connector controllable as GPIO5 and GPIO21. By carefully slicing and soldering wires to a flat cable, these GPIO lines can be broken out onto a breadboard.

There’s a video below demonstrating these GPIO lines being used to control a few LEDs. Of course, anything that is possible with a normal Raspi GPIO is possible with the CSI connector GPIO lines.

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Making luminol from household chemicals

What to make your own chemiluminescent material? Check out this process that uses common household goods to synthesize luminol. You’ll need some lab equipment, and [NurdRage] mentions some precautions to take as luminol is not itself toxic, but some of the fumes and intermediary chemicals found during the process are.

Start by cutting up some vinyl gloves and boiling them with some rubbing alcohol to extract diethyl hexyl phthalate. After filtering, that gets boiled with water and some drain cleaner. The goal here is to continue the process until you have pure phthalic anhydride. Almost done? Not even getting started. This is a very complicated process, but fascinating to watch. After the break you’ll find the full video, or a five-minute abridged version for those that just want a taste of this experiment.

When we looked at the quantum dot manufacturing process a couple of days ago we asked for more chemistry hacks. This is exactly what we were talking about and are thankful that [Rob] sent in the tip. Keep them coming!

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