Voltage dividers are a common circuit to interface high(er) voltage signals to lower voltage interfaces. For some reduction factors like 1:2 it is fairly easy to find the right resistor combination. However the common resistor values are arranged in a rather ingenious way, which can make it difficult to calculate the correct pair for any given reduction factor.

To make this task a bit easier, I wrote a small online tool.

Almost everything a CPU can do can be reduced to some sort of logic equation. In math and theoretical computer science the most common logic operations are AND, OR and NOT. From an electrical point of view NOR and NAND gates are far more popular.

In theory every logic operation can be performed using only NAND gates. In practice it is more useful to use other gates as well. This post will describe how the different gates can be implemented using transistors and why, for my purposes, NAND and NOR are preferable over AND and OR.

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Designing a processor is a common topic during a computer science education. But unless you specialize in computer architecture, you rarely end up building the actual hardware. Even if you do build it, most classes tend to use FPGAs or at least some ready-made hardware parts.

Just for fun, I’ve decided to build my own processor just from basic components.

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A while back, I made a very small AVR programmer, based on [simpleavr]s vusbtiny programmer. Even while I was working on that board, I became annoyed with the fact that more than half of the board was taken up by the USB and ISP connectors.

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I always like a challenge, so when I saw [simpleavr]s vusbtiny programmer, I started to wonder how small I could make an AVR programmer. All in all I’m pretty pleased with the result.

The schematic is almost the same as the original one. I’ve only added a LED and a resistor to indicate a proper power supply.

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