12 Mbps Communication Between A PC And MCU

December 9, 2014 by Brian Benchoff 31 Comments

The world of hobby electronics have only started putting USB in projects for the last few years, and right now, pushing 1.5 Mbps down a USB port is good enough for most cases. This isn’t true for all cases; that’s a terrible data rate, really, and to get the most out of a USB connection, you can at least move up to USB Full Speed and 12 Mbps.

[Linas] is using the STM32F4 microcontroller for this example, an extremely large and very capable chip. [Linas] is using FTDI’s FT2232D USB UART to send data from an SPI port over USB. This chip does support 12 Mbps, but only after a few additions; an external EEPROM must be connected to the FTDI chip to provide a USB 2.0 device descriptor, otherwise the connection between the microcontroller and a computer is limited to 1.5 Mbps. Even using the USB on the STM32 would be a bottleneck in this case; [Linas] is moving data out of the processor using only the DMA controller – using the USB on the STM32 would eat up processor cycles in the microcontroller.

Thanks to the DMA controller inside the STM32, the microcontroller is capable of sending and receiving data through SPI at the same time. The STM32 is capable of reading and writing to the Tx and Rx buffer at the same time, but the computer is only capable of half-duplex operation – it can only read or write at any one time. [Linas] is setting up the DMA controller on the STM32 as a circular mode, putting everything in the buffer into the FTDI chip, and reading everything sent from the computer back into the STM32’s memory. After counting off the correct number of packets. the controller resets everything, moves the circular buffer back to the beginning, and starts the whole process over again.

The circuit was prototyped with an STM Discovery board. With Labview, [Linas] can see the bits coming out of the microcontroller, and send some bits back to the micro over USB. [Linas] has an extraordinarily detailed video tutorial on this project. You can check that out below.

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A Calculator With Free Software And Open Hardware

December 9, 2014 by Bryan Cockfield 57 Comments

We’re fond of open source things here. Whether it’s 3D printers, circuit modeling software, or a global network of satellite base stations, the more open it is the more it improves the world around us. [Pierre Parent] and [Ael Gain] have certainly taken these values to heart with their open handheld graphing calculator.

While the duo isn’t giving away the calculators themselves, they are releasing all of the hardware designs so that anyone can build this calculator. It’s based on a imx233 processor because this chip (and most everything else about this calculator) is easy to source and easy to use. That, and there is a lot of documentation on it that is in the public domain. All of the designs, including the circuit board and CAD files for the case, are available to anyone who is curious, or wants to build their own.

The software on the calculator (and the software that was used to design the calculator) is all free software too. The calculator runs Linux (of course) and a free TI simulator environment in the hopes of easing the transition of anyone who grew up using TI’s graphing calculators. The project is still in a prototype phase, but it looks very promising. Even though the calculator can already run Pokemon, maybe one day it will even be able to run Super Smash Bros as well!

Retrotechtacular: Supersonic Transport Initiatives

December 9, 2014 by Kristina Panos 17 Comments

In the early days of PBS member station WGBH-Boston, they in conjunction with MIT produced a program called Science Reporter. The program’s aim was explaining modern technological advances to a wide audience through the use of interviews and demonstrations. This week, we have a 1966 episode called “Ticket Through the Sound Barrier”, which outlines the then-current state of supersonic transport (SST) initiatives being undertaken by NASA.

MIT reporter and basso profondo [John Fitch] opens the program at NASA’s Ames research center. Here, he outlines the three major considerations of the SST initiative. First, the aluminium typically used in subsonic aircraft fuselage cannot withstand the extreme temperatures caused by air friction at supersonic speeds. Although the Aérospatiale-BAC Concorde was skinned in aluminium, it was limited to Mach 2.02 because of heating issues. In place of aluminium, a titanium alloy with a melting point of 3,000°F is being developed and tested.

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Scope Noob: Microcontroller Quirks With DDS

December 9, 2014 by Mike Szczys 40 Comments

In this installment of Scope Noob I’m working with Direct Digital Synthesis using a microcontroller. I was pleasantly surprised by some of the quirks which I discovered during this process. Most notably, I had a chance to look at errant triggers solved by using holdoff and a few timing peculiarities introduced by my use of the microcontroller. Here’s a video synopsis but I’ll cover everything in-depth after the break.

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Clap On! A Breadboard

December 9, 2014 by Brian Benchoff 11 Comments

The Clapper™ is a miracle of the 1980s, turning lights and TVs on and off with the simple clap of the hands, and engraving itself into the collective human unconsciousness with a little jingle that implores – nay, commands – you to Clap On! and Clap Off! [Rutuvij] and [Ayush] bought a clap switch kit, but like so many kits, this one was impossible to understand; building the circuit was out of the question, let alone understanding the circuit. To help [Rutuvij] and [Ayush] out, [Rafale] made his own version of the circuit, and figured out a way to explain how the circuit works.

While not the most important component, the most obvious component inside a Clapper is a microphone. [Rafale] is using a small electret microphone connected to an amplifier block, in this case a single transistor.

The signal from the microphone is then sent to the part of the circuit that will turn a load on and off. For this, a bistable multivibrator was used, or as it’s called in the world of digital logic and Minecraft circuits, an S-R flip-flop. This flip-flop needs two inputs; one to store the value and another to erase the stored value. For that, it’s two more transistors. The first time the circuit senses a clap, it stores the value in the flip-flop. The next time a clap is sensed, the circuit is reset.

Output is as simple as a LED and a buzzer, but once you have that, connecting a relay is a piece of cake. That’s the complete circuit of a clapper using five transistors, something that just can’t be done with other builds centered around a 555 timer chip.

Overhauling A 3-Zone Reflow Oven

December 9, 2014 by Ethan Zonca 9 Comments

[Ed] owns a 3-zone reflow oven (which he coincidently uses to manufacture reflow oven controllers), but its performance has gotten worse and worse over time. The speed of the conveyer belt became so inconsistent that most boards run through the oven weren’t completely reflowed. [Ed] decided to rip out the guts of the oven and replace it with an Arduino, solving the belt problem and replacing the oven’s user-unfriendly interface

When [Ed] was looking into his belt speed problem, he discovered that the belt motor was controlled by an adjustable linear regulator with no feedback. Although this seems a bit sketchy by itself, the motor also had some mechanical issues and [Ed] ended up replacing it entirely. After realizing that closed-loop speed control would really help make the oven more consistent, [Ed] decided to overhaul all of the electronics in the oven.

[Ed] wanted to make as little custom hardware as possible, so he started out with an Arduino Mega and some MAX31855’s that measure multiple thermocouples in the oven. The Arduino controls the belt speed and runs PID loops which control heating elements in each of the oven’s 3 zones. The Arduino can be programmed with different profiles (stored in EEPROM) which are made up of 3 zone temperatures and a conveyor speed. Don’t have a 3-zone oven of your own to hack? Check out some DIY reflow oven builds we’ve featured before.

Ephemeral Photographs Staged With Artful Inventions

December 8, 2014 by Sarah Petkus 11 Comments

[Gordon Kirkwood’s] focus as a photographer is in capturing ephemeral phenomena, that is, things that are exhilarating to see but also fleeting. In the pursuit of documenting such blips of beauty found in the natural word, he has taken on engineering the circumstance through which they occur by means of technology.

One of the amazing mechanical creations he’s constructed to aid in his photography is a large computer controlled, bubble blower. A few stepper motors work to dilate three segments of soap-soaked rope engaged at 120 degree angles to create a triangular aperture. When the aperture closes, the segments overlap slightly, covering themselves with a consistent coating of suds. When the segments stretch apart, a fan blows a current of air towards the center, pushing the sheath of fluid into ginormous glimmering orbs which he uses as the focal point in some of his photographs.

More currently, [Gordon] has been developing a body of work that involves zapping botanical subject matter with a quarter-million volts from a portable arc producing device he’s created and capturing the reaction with an ultra low-tech camera (the kind with the bellow and sheet you hide under while exposing the film). Using a method all his own, the shots recorded on large format film are claimed to turn out with even more clarity than any current digital camera in use today. [Gordon] has launched a crowd funding campaign to support a pilgrimage to the majestic island of Hawaii, where he’ll use his lightning producing apparatus on ten different specimens of tropical plant life so that he can record the outcome with his tried and proven technique. (see below an artsy shot of his lightning summoner)

Sometimes Kickstarter isn’t so much about commercialism as it is starting a dialogue with the world and beginning a personal adventure. May the journey lead to new inventions and larger, more ambitious projects! Oh yeah- the bubble blowing machine is a must-see in action. Wicked cool:

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