Message Boards Message Boards

3
|
7168 Views
|
0 Replies
|
3 Total Likes
View groups...
Share
Share this post:

Creating a CPU fan monitor with the RPi

Sadly, I've had to do things like work instead of play with my Raspberry Pi, but I was able to squeeze in a small project that may be of interest to others. I wanted to be able to view the current CPU temp and fan speed of my desktop while in a full-screen application, so I created a WL-RPi solution to grab information from the temp/fan log and display it on an LCD Pi plate (by Adafruit).

enter image description here

Details of the design are on my website and the code is available at my github repository.

Previously, I created some WolframLink code to use the Wiring Pi libraries in Mathematica. This project utilizes that code to print to the LCD screen and create custom character definitions for displaying a rudimentary plot of CPU temperature vs. time. I spent some time working on the plot in order to get a smooth and efficient result. Originally tried playing around with Binarize and Rasterize on a ListPlot of the data that I wanted to plot; however this route was a bit too resource intensive and it took several seconds to generate the output. The code below turned out to give me the desired response:

  pmPlotMatrix[data_List]:=Module[{lo = 40,hi=60},
    (* Prevent rescaling problems *)
    lo = Min[data,lo];
    hi = Max[data,hi];
    (* Creates a matrix-style barchart with dimensions *)
    (* amenable to lcdCharDef *)
    1-Normal@SparseArray[
      Flatten@MapIndexed[
        Table[{i,First@#2}->1,{i,#1}]&, 
          (Round@Rescale[#,{lo,hi},{16,1}]&/@data)],{16,20}]
    ];

I avoid all of the graphics generation and instead create a matrix that in turn can be chopped into 5x8 custom characters. I eek out a little more performance by noting that, once the custom characters are on the display, I can just update the character definition which will update the display. This saves several 10's of ms on the screen refresh by not having to run the code to put 8 characters on the screen every iteration.

If anyone is interested, I'd like some input on a bug mentioned at the end of my website discussion of this project. Simply put, a ScheduledTask set to run infinitely will eventually kick me out of the wolfram interpreter and do some whacky stuff to my terminal. I haven't had much time to debug this problem yet.

POSTED BY: BoB LeSuer
Reply to this discussion
Community posts can be styled and formatted using the Markdown syntax.
Reply Preview
Attachments
Remove
or Discard

Group Abstract Group Abstract