Archive for November, 2012

LCD Character Display technical details

I put together a quick tutorial to discuss how I converted the Arduino-specific LCD Char Display Shield to work with the Raspberry Pi. Once everything is hooked up the way I’ve described, you can use it with the libraries that Adafruit has made for the Pi Plate.

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November 25, 2012 at 5:20 pm Leave a comment

LCD Display success

A few weeks ago I bought a LCD Display module from Adafruit. The selling point (for me) was that it has several buttons for navigating options on a headless Pi and an LCD character display to let me know whats going on. Especially for the time-lapse project I’m working on now, where I don’t want to VNC into the Pi to set up the session, this seemed like an ideal solution. As an added bonus, it only uses 2 pins on the GPIO connector, which are already dedicated for I2C communication. What’s not to love?

It actually turned out to be a bit more work than that (it always does, right?) because the module I bought was for the Arduino, which apparently likes to talk over I2C with a 5V pull up… while the Raspberry Pi prefers 3.3V, thank you very much. Adafruit basically states on the product page that it’s only designed for the Arduino, and the Pi is not supported. Fair enough. I should have been paying closer attention.

Except it turned out to be a learning opportunity. You see, the chip they use on the LCD shield (MCP23017) has its own tutorial on the Adafruit site… for extending the number of GPIO pins on the Pi! So I figured, if I can wire up the LCD shield in a similar way, I should at least be able to talk to the MCP23017, and from there I can code the commands to run the LCD character display. 

It turns out that it was pretty simple… just remove R1 and R2 resistors from the LCD shield and the 5V pull up goes away, and the Pi talks just fine to the I2C chip. As an added bonus, Adafruit introduced an LCD shield this past week with a stackable header that is essentially the previous shield with the resistors pulled out. Using the python code they wrote for the new product is totally compatible with my kit, so I was able to get the shield displaying text pretty easily (after I figured out the reason no text was showing up was due to the contrast potentiometer being turned all the way down).

Next step is to fold this into the time-lapse code and make it useful for setting up the pictures. Then I need to sort out how to power this contraption out in the field and I’ll be able to build a board to replace the spagetti of wires I have now!

November 24, 2012 at 3:19 am Leave a comment

Tech Valley Makers Meeting – Nov 28th @ 7pm

I’ve been interested in makerspaces and the maker movement for a while, and there have been rumblings of interest in the Capital District from like-minded individuals. Now things are moving forward, with a meeting on Nov 28th that I’ve helped organize. The details of the meeting are at this announcement site hosted by Google sites. My hope is that there is enough interest to get the community organized and lead to a makerspace / hackerspace and some interesting shared projects.

November 15, 2012 at 9:09 pm Leave a comment

First time-lapse video post

Over the weekend I had my first successful run with the Raspberry Pi controlled camera. I took a time-lapse video of my watch with each frame 59 seconds apart. The results (after running it through a few open source tools to assemble the video) is on YouTube. I’m working on a site to document the project, which can be found here. So far I’ve posted the schematic for the control of the camera (a Canon EOS XSi) and I’m going to be adding the section on USB control and the post-processing steps needed to assemble the video.

November 13, 2012 at 3:07 am Leave a comment

New project: time lapse with the Pi

So in parallel with the stepper business, I’m going to start playing around with using the Pi to control my DSLR for time lapse photography. There are several bits of enabling software to help along, including command-line control over the camera via USB using gphoto. I’ll post more on the results shortly, but I’ve already had some success in controlling the camera following in the footsteps of David Hunt (though without the nice grip!). So far there is not a comprehensive guide for how to do this, so I’ll try to pull something together to save others from the hours of scouring that I did to get things running.

November 3, 2012 at 3:16 pm Leave a comment

Stepper Pepper…

So as mentioned in an earlier post, I’m interested in making my Raspberry Pi control a stepper motor as a first step into the world of physical computing. Not content to simply buy a board (like the StepRocker) that takes care of the grit in this process, I went boldly forth and bought a Pololu carrier board for the A4988 stepper driver (a few of them actually, under the assumption I’ll blow at least one of them up).

Well, it’s not as easy as all that. Without boring into all the minute details, I can say that my early trials have not been encouraging through no fault of the Pi. My latest test last night took the Pi out of the equation and simply used a couple of push-buttons to replace the inputs from the Pi. This has the virtue of being run from the same power supply for both the +5V and +12V lines, and has the fewest variables which are well controlled. Still no success in making *controlled* steps with the motor. The driver will occasionally get into this weird state where it steps the motor 10’s to 100’s of times on it’s own, in a seemingly random direction (though always in the same direction once it gets going). So it very much resembles some sort of demonic possession of circuit… I’m sure of it. 

I’ll continue to mess with it and see if I can figure out what is going on. I suspect that noise or a floating line somewhere is responsible for the random bursts of motion, so tracking that first may help solve the other problem.

November 3, 2012 at 3:10 pm Leave a comment


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