This is a calculator that is similar to the XP PowerToy calculator, but with additional features.

  • Conversion mode: Easily convert between different types of units, say inches to centimeters or teaspoons to tablespoons.
  • Expressions mode: Enter an arbitrary number of expressions and then a formula at the bottom that uses the expressions to produce output. This makes it easy to change the values of the inputs without having to rewrite the whole formula. For example (this is the pythagorean theorum): 
   Expr1=    1
   Expr2=    2
   Formula:  Sqrt(Expr1^2 + Expr2^2)
  • The entry can accept variable assignments and use them in the calculation. Example: a=1; b=2; a + b + a^2 + b^2 outputs 8
  • When entering a calculation, the immediate result is displayed at the bottom. When you hit enter, the entry and the result are added to the history, so you don't lose previous work.
  • Results can be in decimals, hexadecimals, or binary. Numbers can also be entered in these using prefixes of "0x" for hex or "0b" for binary.
  • Results are formatted for easy reading, by grouping digits. For example: 10000+1/128 outputs 10,000. 007 812 5

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Converting version control repositories from Bazaar to Git (bzr to git)

Submitted by drew on

Bazaar is great on Windows. Several years later, git's tools for Windows still.... (ahem) are lacking or too commercial. However, official development on it has ended and git is so much more popular now. So I think the time has come to convert all my beloved bzr repositories to git.

First we need note some prerequisites:

Adding a hardware clock to Raspberry Pi (DS3231)

Submitted by drew on

The popular clock module is uses the DS1307 real time clock chip, which is not very precise. For just a few dollars more, you can get a module with a much more precise DS3231 RTC chip. The one I got was SunFounder's module from Amazon for $9 (free shipping for Prime). It plugs right onto the Raspberry Pi's 40 pin header and doesn't even interfere with the plastic case I have. I have a Model B, but this module should also work on Model A and Model B+. The instructions refer to DS1307, but the chips use the same I2C commands, so it also works for DS3231.

How to run a PiPresents show when you don't have a Raspberry Pi

Submitted by drew on

PiPresents is some pretty cool software that will run a PowerPoint-like presentation. But with lots more flexibility. It was originally written for the Raspberry Pi.

However.... perhaps someone else has your Pi. Perhaps you don't even have one. It is possible to run a PiPresents show on  your good ol' desktop computer (Windows, Linux, or Mac). Here's how.