Spectrum Analyzer Users Custom Characters On An HD44780 Display

September 8, 2011 by Mike Szczys 8 Comments

[Camilo] built a spectrum analyzer to use with his audio system (translate). The hardware is quite simple, using an op-amp, microcontroller and LCD display. He chose an LMV324M low-voltage op-amp which connects to the incoming audio signal and feeds its output to the microcontroller’s ADC. In this case, he chose a Freescale microcontroller from the HCS08 family which is running at 20 MHz. This gives the project enough speed to properly analyze the incoming audio. He mentions that he’s following the guidelines set forth in the Nyquist-Shannon sampling theorem and using the Fast Fourier Transform when processing the samples.

This isn’t the first time we’ve seen a character LCD used as a display for a frequency analyzer. This other ATmega8-based rendition supported several different screen layouts. These displays have enough RAM to store eight custom characters. Each character is 5×8 pixels, lending eight levels to each character for a total of 16 for each column seen above. We love the simplicity of the hardware in the project but we wouldn’t mind seeing an additional potentiometer to fine-tune how the data is displayed on the screen to take advantage of its full range. See the project in action in the clip after the break.

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Want 2 Megabytes Of SRAM For Your Arduino?

September 7, 2011 by Mike Szczys 15 Comments

How much memory do you really need? We suppose it’s not really our place to judge how you ~~misuse~~ use memory in your projects. But we do appreciate the clean and orderly technique that [Eric Rogers] uses to add multiple SPI SRAM chips to an Arduino.

The heavy lifting is done with a CPLD shield called the Amani 64. It intercepts the SPI calls from the Arduino to an SRAM chip, and translates the address information to find the appropriate data on a collection of 23K256 devices. These chips are inexpensive, and using several of them provides a savings over choosing a single SPI addressable chip with a larger memory size.

The best part is that the flexibility of the CPLD allowed [Eric] to devise an addressing system that takes advantage of unused bits in the Arduino’s SPI data transfer functions. When using a single 23K256 chip, there are four write functions that waste a total of six bits. He devised a method to inject addressing data into these unused bits, allowing him to address up to 64 different memory chips for a potential of 2 MB of storage. The CPLD pulls out this injected address and subsequently writes or reads the bank of SRAM chips.

Looking for other SRAM upgrade options? Here’s another one that uses multiplexing to decrease the address lines necessary to add memory.

Beginner Concepts: MOSFETs

September 7, 2011 by Mike Szczys 12 Comments

[Moser’s] introductory guide to MOSFETs serves as a quick introduction for those unfamiliar with the parts. They fill a similar role as a bipolar junction transistor like the 2N2222, making it possible to switch large loads. But fundamentally they are different. Metal Oxide Field Effect Transistors have three pins for Drain, Source, and Gate instead of the Collector, Emitter, and Base that you may be used to. The Gate is the control pin for the device and offers a desirable advantage over bipolar junction transistors in that it is insulated from the channel. This means that much less current flows into the Gate when compared to the Base of a common transistor, saving power and providing protection to the logic circuitry.

Don’t fret if this makes your head spin. [Moser’s] writeup is short and to-the-point but it’s not watered down. You can get a basic overview and if you care to learn more, he’s linked to datasheets and has basic terminology that is easily clarified with a Google search. One of the most powerful tools that he’s included is the simple MOSFET and driver circuit diagram you see above. This makes it possible to switch incredibly large loads very quickly; the true power of the MOSFET.

Defusable Alarm Clock – Wastes Wire But Fun For The Kids

September 7, 2011 by Mike Szczys 36 Comments

Nothing makes you feel the pressure of getting out of bed in the morning like a ticking-time-bomb on the bedside table. It may look like it came in the mail from ACME, but all that went into this is some wooden dowels covered in craft paper and an Arduino-compatible board. The 7-segment display can act as a clock, or count down to your doom. You can set an alarm that requires you to clip the wires to shut it off. Each time that alarm is set the wires are randomly chosen; one will set of the bomb, one will safely defuse it, and the others do nothing. See for yourself after the break.

The wires are easily replaced because they are connected via terminal blocks. It still seems like an awful waste of wire. We like the Think Geek bomb clock concept that works in much the same way but uses wires that have a male/female RCA plug pair that can be disconnected and reconnected without waste.

This one will apparently be available as a kit, at which point the schematics and code will be released. But it shouldn’t be too hard to build one from scratch yourself, and it’s an obvious winner if you’ve got kids.

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TV Retrofit… Because Flatscreens Just Don’t Take Up Enough Space

September 6, 2011 by Mike Szczys 32 Comments

[Igor] helped his friend’s family out by retrofitting an old Philco television with a newer flat panel (translated). The original conked out over thirty years ago, but the look of it still held quite a bit of nostalgia for his girlfriend’s Grandmother. She showed it to him on a recent visit and asked if it could be restored. He told her that it would most likely never work again, but that he could use modern components to replace the screen, while preserving the case itself.

The best thing about old hardware like this is that you can actually get the case apart fairly easily. After removing the tube and electronics he traced a pattern of the opening that he could take along to the electronics store to find a TV which would fill the opening. With the new screen in hand he found that using the threaded holes intended for VESA mounting brackets made it simple to install in the old case. A steel bar bolts onto the plate which he cut and drilled to match the TV’s hole pattern. Now Grandma is happy to have the retro-looking case with a modern high-def picture.

Smartphone Hacking Without Risk – Plus, Broken Phones Needed

September 6, 2011 by Mike Szczys 17 Comments

[Adam Outler] and [Rebellos] have been working feverishly to advance the world of mobile device hacking. They’re attacking on two fronts, making it easier for the common hacker to monkey with the phone’s firmware and OS with impunity, and by finding ways to make regular handsets into dev-hardware for low-level hacking.

The Hummingbird Interceptor Bootloader (HIBL) circumvents the chain of trust on smartphones running the Cortex-A8 family of processors. This opens a lot of doors, not the least of which is the ability to run any OS that you’re capable of porting to the hardware. We’re certain that Android builds will come first as they are open-source, but there’s talk of iOS or Windows Phone being run after some heavy assembly hacking.

But the two developers are trying to bring more people into the fold with their recent hacks. [Adam] has put out a call for your broken hardware. He needs your dead smartphone boards to reverse engineer the circuitry. Soldering one wire from the OM5 pin on the processor to the OM1 resistor will make the phones unbrickable (something we heard about back in July) and remove the need for soldering in a JTAG interface. With borked hardware in hand he pops off the processor and traces out this connection as well as the UART pins.

The soldering isn’t an easy process, but it’s a marked improvement that breaks down more barriers that keep people from hacking their coveted hardware. The clip after the break shows how easy it now is to recover your phone if something goes wrong while messing with the firmware or OS.

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