Photonic Reset of the Raspberry Pi 2

For the past month, the Raspberry Pi 2 has only been available to the Raspi Foundation, and for about 2 weeks, select members of the media who have worn the Raspi 2 on a necklace like [Flavor Flav] wears a clock. That’s not many people with real, working hardware and when a product is released, the great unwashed masses will find some really, really weird bugs. The first one to crop up is a light-sensitive reset of the Raspberry Pi 2.

[PeterO] on the Raspberry Pi forums took a few pictures – with flash – of a running Raspberry Pi 2. It took a little bit of deduction to realize that a camera flash will either reset or turn the Raspi 2 off. Yes, this is weird, and experiments are ongoing.

A short video from [Mike Redrobe] confirms the finding and a reddit thread offers an explanation. U16, a small chip located in the power supply part of the Raspi 2, is sensitive to light. Putting enough photons will cause the Pi to shut down or restart.

There’s still some research to be done, however, I can confirm a cheap green laser pointer will reset a Raspberry Pi 2 when the beam is directed at the U16 chip. This is the chip that is responsible, and this is not an EMP issue. This is a photon/light issue with the U16 chip. The solution to this bug is to either keep it in a case, or put a tiny amount of electrical tape over the chip.

Thanks [Arko] for staying up until an ungodly hour and sending this to me.

A Raspberry Pi SID Player

Of all the vintage chiptune machines out there, the Commodore 64 is the most famous. Even 30 years later, there are still massive gatherings dedicated to eeking out the last cycle of processing power and graphics capability from the CPU and the infamous synth-on-a-chip, the SID. [Bob] wanted to build a SID jukebox. A C64 is capable of the job, but if you want to have every SID composition on an SD card and connect that to a network, a Raspberry Pi is the way to go.

The SID chip, in its 6581 or 8580 versions, is controlled directly by poking registers on the chip through the address and data busses. This means a lot of pins, too many for the original Raspi expansion header. That’s not a problem that can’t be solved with a few shift registers, though. The rest of the circuit is an LM386 audio amplifier, an LCD that displays the current song, and a can crystal oscillator for the SID.

Right now everything is wired up on a breadboard, but making this a Raspberry Pi hat would be a rather simple proposition. It’s only a matter of finding a SID with working filters, and if you can manage that, it’s a pretty easy build to replicate. Video below.

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Benchmarking The Raspberry Pi 2

The Raspberry Pi has only been available for a few days, but already those boards are heading through the post office and onto workbenches around the world. From the initial impressions, we already know this quad-core ARMv7 system boots in about half the time, but other than that, there aren’t many real benchmarks that compare the new Raspberry Pi 2 to the older Raspi 1 or other similar tiny Linux dev boards. This is the post that fixes that.

A word of warning, though: these are benchmarks, and benchmarks aren’t real-world use cases. However, we can glean a little bit of information about the true performance of the Raspberry Pi 2 with a few simple tools.

For these tests, I’ve used Roy Longbottom’s Raspberry Pi benchmarking tools, nbench, and a few custom tools to determine how fast both hardware versions of the Raspberry are in real-world use cases.

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Introducing the Raspberry Pi 2

TL;DR It’s called the Raspberry Pi 2 Model B. Quad core ARM Cortex A7 with one Gig of RAM. It’s the same form factor as the Raspberry Pi Model B+. Available now at Newark, Element 14, Allied, and RS Components. It’s the same price as the old one. You’re not a child and you should learn to read.

The original Raspberry Pi released, three years ago, was looking a bit long in the tooth when it was first launched. That’s to be expected for a computer that sells for $35 USD. Three years is a long time in the world of electronics, and the Pi is due for an update. It’s here, now, and the biggest change is a faster quad-core chip, a better processor architecture, and 1GB of RAM.

The Raspberry Pi 2 Model B features a quad-core ARM Cortex A7 running at 1GHz with 1GB of RAM. This chip uses the ARMv7 architecture instead of the ARMv6 of the original Raspi. When playing around with it, it was noticeably zippier than my months-old Raspi Model B in web browsing tasks. Very, very cool, and something that opens up a few doors for CPU-intensive applications.

Although the CPU has been updated, there isn’t much else on the Pi that has changed. USB and Ethernet is still handled by the LAN9514 USB/Ethernet controller. If you’re looking for Gigabit Ethernet, sorry that’s not going to happen. We’re not going to get eMMC Flash, SATA ports, or anything groundbreaking other than the CPU with this hardware update. It’s pretty much just a CPU and RAM upgrade.

All the original ports found on the Raspberry Pi Model B+ are found on the Raspi 2; HDMI, audio, analog video, Ethernet, USB, CSI, the as-for-now unused DSI, and GPIO ports haven’t changed. Again, we’re looking at a CPU and RAM upgrade with this hardware release.

Instead of the odd Package On Package CPU and RAM stack featured in previous Raspberry Pis, the RAM has now moved to the back on the Raspi 2:


The RAM chip is an Elpida EDB8132B4PB-8D-F, an eight gigabit DDR2 RAM that has the same clock rate as the RAM in the original Raspi. Don’t look for an increase in memory performance or speed. Instead, just be glad there’s now a full gigabyte of RAM on the Raspi.

A few of you may remember the ‘upgrade’ all those Raspberry Pi early adopters missed out on. After the first few hundred thousand Raspberry Pi Model Bs shipped, someone realized they could upgrade the RAM from 256 MB to 512 MB. It is not yet known whether the Raspberry Pi 2 will be upgraded as easily. Sixteen gigabit RAMs do exist, but now that the CPU and RAM aren’t on the same package, there’s more to consider than just plopping down a new RAM chip.

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Dedicated Automobile Traffic Monitor with Raspberry Pi

[j3tstream] wanted an easier way to monitor traffic on the roads in his area. Specifically, he wanted to monitor the roads from his car while driving. That meant it needed to be easy to use, and not too distracting.

[j3tstream] figured he could use a Raspberry Pi to run the system. This would make things easy since he’d have a full Linux system at his disposal. The Pi is relatively low power, so it’s run from a car cigarette lighter adapter. [j3tstream] did have to add a custom power button to the Pi. This allows the system to boot up and shut down gracefully, preventing system files from being corrupted.

After searching eBay, [j3tstream] found an inexpensive 3.2″ TFT LCD touchscreen display that would work nicely for displaying the traffic data. The display was easy to get working with the Pi. [j3tstream] used the Raspbian linux distribution. His project page includes a link to download a Raspbian image that already includes the necessary modules to work with the LCD screen. Once the image is loaded, all that needs to be done is to calibrate the screen using built-in operating system functions.

The system still needed a data connection. To make things simple and inexpensive, [j3tstream] used a USB WiFi dongle. The Pi then connects to a WiFi hot spot built into his 4G mobile phone. To view the traffic map, [j3tstream] just connects to a website that displays traffic for his area.

The last steps were to automate as much as possible. After all, you don’t want to be fumbling with a little touch screen while driving. [j3tstream] made some edits to the LXDE autostart file. These changes automatically load a browser in full screen mode to the traffic website. Now when [j3tstream] boots up his Pi, it automatically connects to his WiFi hotspot and loads up local traffic maps.

Multiplexing Pi Cameras

The Raspberry Pi and its cool camera add-on is a great way to send images and video up to the Intertubes, but what if you want to monitor more than one scene? The IVPort can multiplex up to sixteen of these Raspi camera modules, giving the Pi sixteen different views on the world and a ridiculously high stack of boards connected to the GPIO header.

The Raspberry Pi’s CSI interface uses high-speed data lines from the camera to the CPU to get a lot of image data quickly. Controlling the camera, on the other hand, uses regular old GPIOs, the same kind that are broken out on the header. We’ve seen builds that reuse these GPIOs to blink a LED, but with a breakout board with additional camera connectors, it’s possible to use normal GPIO lines in place of the camera port GPIOs.

The result is a stackable extension board that splits the camera port in twain, allowing four Raspi cameras to be connected. Stack another board on top and you can add four more cameras. A total of four of these boards can be stacked together, multiplexing sixteen Raspberry Pi cameras.

As far as the obvious, ‘why’ question goes, there are a few interesting things you can do with a dozen or so computer controlled cameras. The obvious choice would be a bullet time camera rig, something this board should be capable of, given its time to switch between channels is only 50ns. Videos below.

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Custom Raspberry Pi Thermostat Controller

Thermostats can be a pain. They often only look at one sensor in a multi-room home and then set the temperature based on that. The result is one room that’s comfortable and other rooms that are not. Plus, you generally have to get up off the couch to change the temperature. In this day and age, who wants to do that? You could buy an off-the-shelf solution, but sometimes hacking up your own custom hardware is just so much more fun.

[redditseph] did exactly that by modifying his home thermostat to be controlled by a Raspberry Pi. The temperature is controlled by a simple web interface that runs on the Pi. This way, [redditseph] can change the temperature from any room in his home using a computer or smart phone. He also built multi-sensor functionality into his design. This means that the Pi can take readings from multiple rooms in the home and use this data to make more intelligent decisions about how to change the temperature.

The Pi needed a way to actually talk to the thermostat. [redditseph] made this work with a relay module. The Pi flips one side of the relays, which then in turn switches the buttons that came built into the thermostat. The Pi is basically just emulating a human pressing buttons. His thermostat had terminal blocks inside, so [redditseph] didn’t have to risk damaging it by soldering anything to it. The end result is a functional design that has a sort of cyberpunk look to it.

[via Reddit]