February 2012
16 posts
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New Project: AVR Programmer
I’ve been trying to break the Joust rebuild project into meaningful chunks. My recent attempt at designing a circuit for manufacture in EAGLE didn’t pan out; it seemed both too big, because I hadn’t yet breadboarded all the sub-circuits as a single large circuit, and at the same time too small, because it would have been little more than those simple sub-circuits that I had...
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Wanted: CLI EDA
That’s command-line interface electronic design automation.
I’m surprised that hardware engineers design schematics and circuit boards graphically. By that I mean that they drag shapes around in a GUI editor. Behind the scenes all the polygons and line segments are being represented much more simply as Component A, Pin 1 being connected to Component B, Pin 2, or Component C at...
Free Range VHDL →
This is a revised version of The Lo-Carb VHDL Tutorial and the Shock and Awe VHDL Tutorial, both by Bryan Mealy. Recommended.
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Maxim DS1077 Programmable Oscillator
The Maxim DS1077 is a programmable oscillator. Instead of ordering different oscillators for each different project you have, you get just one on a SparkFun breakout board and program it, using I2C, for whichever frequency you need.
And in fact, after some stumbles on my part, yes, it works.
Things I Learned About the DS1077, The Hard Way
The I2C interface (a.k.a. TWI or two-wire interface)...
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Son of '9572 is alive
A good night’s rest didn’t help the ‘9572. It remains destroyed. After talking it over with a few people, I believe any of the following is possible:
It was close to death already from having powered it from 5 volts for so long, and it simply gave out.
I was careless with a logic probe pin and briefly touched two opposing outputs.
While juggling pins on the UCF, I uploaded a...
On the Origin of Circuits →
Dr. Thompson peered inside his perfect offspring to gain insight into its methods, but what he found inside was baffling. The plucky chip was utilizing only thirty-seven of its one hundred logic gates, and most of them were arranged in a curious collection of feedback loops. Five individual logic cells were functionally disconnected from the rest– with no pathways that would allow them to...
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The '9572 is dead
I killed my CPLD Breakout Board. While taking pictures of the “successful” SRAM-loading VHDL I’d written and wired up, I noticed that the power LED on the board was off. I checked the connections, toggled the power a few times, tried re-running the logic analyzer, and eventually concluded that the board was dead. It draws 1.4 amps when I plug it in, and the CPLD itself gets...
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The 6502: A Documentary →
Go Quinn! Go Bill!
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TTL Voltage and Current Cookbook Recipe
Now that I’m able to do something with this CPLD, I’ve been concerned about replacing $10 of discrete logic chips with a $2 chip that needs $8 of level shifters. Though the Xilinx XC9572XL is a fairly modern 3.3-volt device, I know its I/O pins are 5-volt tolerant, meaning that I can send in a 5-volt signal from my circa-1980s 5-volt 6809E. But the ‘72’s output voltage is...
More than you ever wanted to know about electrical...
A few days ago I posted a very confused question about JTAG signals. Here is my less confused answer.
You’ve surely seen the cup-or-face picture before, where some see two people looking at each other, and others see a single white chalice in the middle. Both groups are correct, and fortunately everyone can easily tell their brains to see the other image, too. That’s what happened...