A Truly Professional Raspi Analog Input

September 14, 2012 by Brian Benchoff 37 Comments

Much to the chagrin of hardware tinkerers, the Raspberry Pi doesn’t have analog inputs on its GPIO pins. Sure, you can blink a LED with just a few console commands, but reading sensors with a bone-stock Raspi requires a little additional hardware. [Brian Dorey] just released a board that allows for 8 analog inputs on the Raspberry Pi with a 16-bit resolution that is much higher than any Arduino-based build.

[Brian]’s build is based on an earlier, similar iteration of a Raspi analog board we saw last July. Like the previous version, the new professionally made PCBs use a pair of Microchip MCP3428 analog to digital converter. These ADCs are able to sample four channels at a resolution of 16 bits; a vast improvement over the 8-bit ADCs included on every Arduino.

The boards communicate with the Raspberry Pi over an I2C serial bus using a neat stackable header. In theory, it should be possible to use several of these boards and measure dozens of analog channels, but we’ll leave a demonstration of that up to [Brian].

3D Printer Control For The Raspi

September 13, 2012 by Brian Benchoff 27 Comments

Instead of dedicating his laptop to control his RepRap all night, [Walter] is using a Raspberry Pi as an Internet-enabled front end for his 3D printer.

Before [Walter] got his hands on a Raspberry Pi, he set up his laptop next to his RepRap and let the machine do its work for hours on end. Obviously, this tied up his laptop for a while so when his Raspi was delivered he was eager to offload the responsibilities of controlling a printer to his new Linux board.

Right now, [Walter] has his Raspberry Pi set up as a web interface able to control his printer similar to Pronterface. We have to note that the Raspberry Pi isn’t driving servos or feeding filament onto the bed; those responsibilities are still handled by the RepRap electronics, but the ability to use a 3D printer over the web is still pretty cool.

[Walter] is putting the finishing touches on his 3D printer web interface, after which he’ll upload everything onto the git. Planned features for future updates include uploading gcode from the web and an option to connect a webcam for visual feedback when controlling a remote printer.

Video demo after the break.

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Raspy Juice Gives You Serial Ports And Servo Control

September 13, 2012 by Brian Benchoff 21 Comments

Up next on the continual march of expansion boards for the Raspberry Pi is the Raspy Juice, a board designed to break out the GPIO pins on the Raspberry Pi into servo, serial, and other miscellaneous connections.

The Raspy Juice features an ATMega168A microcontroller connected to the Raspberry Pi as an I2C slave device. Not only does the addition of a microcontroller add analog inputs to the Raspberry Pi, but also RS232 and RS485 serial connections, a real-time clock, and four JST plugs for hobby servos.

Because the Raspberry Pi can be powered from the GPIO header, the creator, [NTT] added a buck regulator so batteries or solar cells can be used to power the Raspberry Pi.

The Raspberry Pi is a terribly awesome robotics platform, but sadly limited by its capability to drive motors and servos natively. The Raspy Juice adds some much-needed capability to the Raspberry Pi, and we can’t wait to see a robot take its first steps with this expansion board.

64 Rasberry Pis Turned Into A Supercomputer

September 12, 2012 by Brian Benchoff 71 Comments

In retrospect, it was only a matter of time before someone turned a bunch of Raspberry Pis into a supercomputer.

The Raspi supercomputer is the result of a project headed up by University of Southampton professor [Simon Cox]. Included in the team are a gaggle of grad students and [Simon]’s 6-year-old son who graciously provided the material, design, and logistics for the custom LEGO case.

The Iridris-Pi supercomputer, as the team calls their creation, consists of 64 Raspberry Pis, all configured for parallel processing using a lightweight version of MPI. [Simon] was kind enough to put up an excellent guide for turning two (or more) Raspberry Pis into a supercomputer.

The machine has a full 1 TB of disk space provided by a 16 GB SD card in each node. Although the press release doesn’t go over the computational capabilities of the Iridris-Pi, the entire system can be powered from a single 13 A supply.

If you’re wondering what it would take to get a Raspberry Pi supercomputer into the TOP500 list of supercomputers, a bit of back-of-the-envelope computation given the Raspi’s performance and the fact the 500th fastest computer can crank out about 60 TeraFLOPS/s, we’ll estimate about 1.4 Million Raspis would be needed. At least it’s a start.

Using A Raspberry Pi As Your Travel Computer

September 11, 2012 by Mike Szczys 29 Comments

Do you think you could travel for the entire summer and leave your laptop at home? [Gef] did just that. With the help of his Kindle he used a Raspberry Pi as his travel computer. This was an easy association to think up, since he planned to bring the Kindle along as his reading material anyway. All it was going to take was some creative hacking to get it working as a display for the single-board computer.

The Kindle is merely connecting to the Raspberry Pi through a terminal emulator. This happens via USB, and requires that you Jailbreak the kindle and install a package called USBnetwork. The problem with the technique is that you’re going to go crazy trying to use the tiny keyboard that is built into the eBook reader. [Gef] decided to take a USB keyboard along with him, but how is he going to use it to control the terminal screen on the Kindle? The answer is the ‘screen’ application. We’ve used it a lot to keep programs running on a machine after we’ve exited from an SSH session. It turns out it can also be used to host multiple users on the same terminal session. Pretty neat!

[via Make]

Getting Around The Raspi’s USB Host Current Limit

September 10, 2012 by Brian Benchoff 26 Comments

For being such a revolutionary device, there are still a few problems with the Raspberry Pi. For one, the USB host ports are only able to source 140 mA per port, while the USB ports on your desktop, laptop, and even tablet are able to send a full 500 mA per port.

The official ‘fix’ for this problem is to use a powered USB port for any device that requires more than 140 mA, something that didn’t sit well with [Manis]. He came up with an easy fix , though, that only requires a few bits of wire and a soldering iron.

The USB ports on the Raspi are current limited to 140 mA by a pair of polyfuses. [Manis] bridged these fuses, effectively taking them out of the circuit with a short length of wire. This allowed him to use a USB hard drive (powered by USB, of course) with the Raspi.

There’s one small problem with sending that much current through the Raspi’s USB port. Sometimes, when the high-power USB device is powered on, the voltage will sag, resetting the SoC and rebooting the system. [Manis] did his homework and discovered USB 2.0-spec ports should use a 120 μF, low-ESR capacitor to prevent this. The Raspi comes stock with a 47 μF cap used for this purpose. Replacing this cap (C32) might be a good idea if you’re planning on using high-power devices with your Raspi.

Problems Powering Raspberry Pi From GPIO Header

September 4, 2012 by Mike Szczys 38 Comments

[Zaion] grabbed an ATX power supply to source the 5V the Raspberry Pi needs to run. The common problem when it comes to RPi supplies is a shortfall in how much current a USB wall adapter can source. The ATX shouldn’t have this problem, but none-the-less he found that the USB ports were only reading about 5V. Strange. He grabbed the soldering iron and fixed the issue with a piece of jumper wire (English translation found in the second half of his post).

The problem was discovered when trying to get a WiFi dongle to work on one of the RPi’s USB ports. It simply wouldn’t show up, and after going down the blind alley of assuming it was a driver problem he started to investigate the hardware. After discovering the below-nominal voltage [Zaion] measured the resistance between the 5V pin on the GPIO header and the one on the USB port. It reads 3-4 Ohms and he concluded that the trace is too thin. We took a quick look at the schematic for the board and see no reason for the voltage drop. His jumper wire fixed the issue but it leaves us wondering, is this an isolated case, or a design flaw? Tell us what you think in the comments section.