Tag Archives: handheld


I made a promise that I would have some extra info on stepper motors, and clearly this isn’t it. I got very distracted with the parallel port work. Parallel port stuff used to be easy in Win98 and earlier, but got more difficult in XP. By more difficult I mean I had to install “inpout32.dll” and do some funky stuff in C#. But to use “inpout32.dll” you have to know the I/O start address, so I started blindly running towards what I thought the solution was.

To find out your start address you can simply head to Device Manager, open up the LPT tab, and click on Resources. For me, the I/O range starts at 0378. This is not the value you want, as it is the HEX representation of the address. As it turns out the integer address is 888. To save the user from going through these steps I had to dip into WMI and extract the information from there. Now there is no one place where you can tie together “LPT” and port address, so I had to connect them together using the PnPDeviceID. This took me ages to figure out as I had never used WMI before. Long story short, I have got the stepper turning controlled from the parallel port and also from a PIC from RS232.All I need to do is write the article, and generate some usable schematics.

However, I got distracted by designing something for my kids to play with. As an engineer I can’t help but be critical of a large number of children toys. I am not including things like Mindstorms, but I guess you get what you pay for. I want to show my children that electronics isn’t magic. They all use technology in one form or another, but I don’t want them to take it for granted. I want to show how a TV remote works, and how they can use something instead of the remote to change channels.

At the moment I have specced out some features, and it has already suffered from significant feature creep:

  • Fit inside a dual gang back box (850x1470x35mm)
  • Clear acrylic lid to show electronics
  • Attempt to route everything on top layer
  • 16 red/green LEDs
  • 16 tactile switches
  • 16×2 LCD display
  • Rotary encoder
  • Powered from 4 rechargeable batteries
  • Small prototype area

I want to make sure this will grow as they do, and have features so it will entertain all of them (20months – 6 years). There is little doubt that it will remain interesting for all of 5 minutes, but that is no different from any of their toys. Currently I am deciding whether I should include any IR LEDs for controlling the TV, or  Sparkfun’s 3-axis gyroscope. I’ve even got a small touchscreen digitizer that could make its way inside. And of course there is always room for a little speaker.

Clearly, there is some more feature creep to go.