Want 2 megabytes of SRAM for your Arduino?

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.

Disco isn’t dead: diy dance floor spotted at student parties

Your party is lame if it doesn’t include interactive blinking lights on the dance floor. [Mario] and [Lukas] didn’t want to have lame parties, so they enlisted some fellow students to build an interactive dance floor (translated). The finished party-piece is 4 meters by 2.5 meters (that’s about 13′x8′ for us yanks) and includes 160 lighted squares. But it’s the electronics that really make this a heavy project.

Milled into the underside of the pressboard base are a series of pockets and channels to hold various components. If you look hard enough, you’re going to find eight AVR microcontrollers which control the LEDs, 8 CPLDs to manage the weight sensors which make the floor interactive, and an FPGA and embedded computer to tie everything together. It’s movable, a hit at parties, and so far it seems to hold up to the occasional spilled beverage.

You can’t share a project like this without some video. See it after the break.

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Dabbling with CPLD generated VGA signals

It seems like all the cool kids are leaving the 8-bit hobby microcontrollers in the parts bin and playing with more advanced parts like Complex Programmable Logic Devices. [Chris] is no exception to the trend, and set out to generate his own VGA signal using one of the beefy semiconductors.

It seems that he’s using the acronyms CPDL and FPGA interchangeable in his post but according to the parts list this setup uses an Altera EPM7128SLC84-7N CPLD. In order to generate the VGA signal he needed a way to convert the digital signals from the chip into the analog values called for in the video standard. He chose to build a Digital Analog Converter for the RGB color values using a resistor network which he calculated using PSpice. The other piece in the puzzle is a 25.175 MHz oscillator to clock the CPLD. As you can see after the break, his wire-wrapped prototype works exactly as designed. The example code generates the rainbow bars seen above, or a bouncing box demo reminiscent of a DVD player screen saver.

Want to know more about programming CPLDs? We did a tutorial on the subject a while back.

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Emulating Oric-1 floppy disk hardware

This device is called the Cumulus and it’s used to emulate the floppy disk hardware for Oric-1 and Oric Atmos computers. These 1980′s era computers included an expansion slot to which you could connect a floppy drive. That module, called a Microdisc system, also included the driver circuit which means you can’t just use a modern-day floppy drive as a replacement. [Retromaster] sidestepped the need for magnetic media all together by building an SD card interface which emulates the original module. We can tell by the use of a color screen and clean board layout that a lot of love went into the project. A CPLD implements the communications protocol used by the Microdisc system and creates all of the registers that would have been found on the original hardware. A PIC takes care of the SD card communications and the user interface.

With the exception of comforting noises, we’d bet there are few who have fond memories of using floppy disks. No wonder we’ve been seeing hacks to replace them quite a bit lately.

What Development Board to Use? (Part Two)

We asked for responses to our last Development Board post, and you all followed through. We got comments, forum posts, and emails filled with your opinions. Like last time, there is no way we could cover every board, so here are a few more that seemed to be popular crowd choices. Feel free to keep sending us your favorite boards, we may end up featuring them at a later date!

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V4Z80P: The 8-bit laptop

[Phil] over at Retroleum has cobbled together a clean, well put together laptop based entirely around a Zilog Z80 microprocessor and a pair of Spartan II FPGAs. These FPGAs allow him to reduce the number of devices on his board, and therefore cut his production cost as well as device size. He even managed to integrate a salvaged PSOne screen. The laptop comes complete with [Phil]‘s own Homebrew OS as well as a great graphical vector based demo.

Sure he’s updated the project in recent years to shrink the board, speeding up the Z80, and increasing the peripheral speed and functionality, but we’re suckers here for a total package hack. Seriously though, check out the newest version of the device as well as the backlog that shows the project growing over time.

Thanks to [Steth] for the heads up.

40 MSPS Digital oscilloscope

If you can fabricate single-sided circuit boards at home you can build this digital oscilloscope. It uses mostly through-hole components with just a couple of surface mount chips to contend with. An ATmega162 handles the hardware end of things with a CPLD used to manage the sampling rate. Data is displayed on a 240×128 LCD display which will be the most expensive component to acquire. It’s still a lot cheaper than buying a commercially available oscilloscope, even if you get a base model and hack it to unlock all the features.

[Thanks Juan]