Dynamic Stripchart Image Generator

Phil Pilgrim (PhiPi)

Continuing my quest to create dynamic image content with the Spinneret, I've come up with an object that produces strip charts, like this one:

The image is a bitmap (.bmp). This format was chosen because it's paletted and does not require an image-compression algorithm to produce. The following aspects of the stripchart are programmable:

• Width (up to 496 active pixels, 512 pixels total)
• Height
• Horizontal scaling
• Paper color
• Grid spacing and color
• Pen color

The image is generated one line at a time, starting from the bottom (the natural order for .bmp images) and requires only enough buffer space for one line. That way, a 256- x 400-pixel stripchart image that would normally require 51.2K bytes of RAM to draw in situ needs just a 128-byte line buffer (plus some auxiliary variables) to produce and ship off to the HTTP client for display on a webpage.

Here's a link to my SpinneretCAM web server with another stripchart example:

http://phipi.homelinux.org:3456/stripchart.bmp

That image is produced with using the following code snippets:

  cht.new(201, 400, 20, 16, $eeffee, $aaffaa, $ff0000, -$1_0000, $1_0000, @cht_buffer) 'Create chart specs.
  repeat i from 0 to 800
    cht.add_datum(sin(i << 5))    'Fill the chart with data.
...

  cht.begin 'Begin a new          'Generate a chart, and send it to the client.
  repeat while i := cht.block
    server.array(i, cht.block_size)
  server.end_custom_content

Typically, the chart would not be filled with data all at once, but one datum at a time at scheduled intervals, with the excess scrolling off the bottom. Such data often represent time sequences such as line voltage, temperature, windspeed, humidity, etc.

The objects in the attached archive are autodocument-ready and can be uploaded to read in document format here:

http://www.phipi.com/spin2html

-Phil

D.P

All I can say is extremely cool and thanks for all you do on this forum.

Phil Pilgrim (PhiPi)

The stripcharts are now live and updating continuously (every five minutes). You can see them here:

http://phipi.homelinux.org:4567

Here's a photo of the Spinneret server that creates them, with a TSL230 light-to-frequency sensor and a DS1620 temperature sensor:



The two sensors are multiplexed, as described in this thread:

http://forums.parallax.com/showthread.php?130253-Multiplexing-a-DS1620-(temp)-with-a-TSL230-(light)

I've got it sitting in my living room next to a window. You should be able to tell when I turned the room lights on in the evening and then off when I hit the sack.

-Phil

Mike G

Hey Phil, I'm getting a timeout.

Phil Pilgrim (PhiPi)

Oh, sorry about that. I had the NAT misconfigured in my firewall and, of course, hadn't tested it this time with my external website's reflector script. Try it now.

-Phil

Mike G

Still getting a timeout
http://phipi.homelinux.org:4567

Phil Pilgrim (PhiPi)

Oh, drat! It locked up; so I had to reset it, which means the data that it collected got lost. Anyway, here's what was there before it locked up:



Now you'll have to wait an hour or so before any interesting trends appear.

-Phil

Mike G

That is damn cool Phil.

mindrobots

BRAVO!!

This is excellent. Time to put my local environment online.

Rick

Ltech

Push to facebook and put some heartbeat monitoring ....
Connecting " virtual" and "physical" life ?

Great !

I need it for remote monitoring server temp/power rooms and racks

Tumbler

Nice work Phil,
Seems you are working on a GD2 processor
Now it needs some compression (to jpeg or so)

Phil Pilgrim (PhiPi)

Yes, Ive considered a more generalized graphics generator. The idea would be to accept GD-like commands to create a display list, and then cycle through the display list once for each row of the image as it's being generated. The objective is to keep from having to generate a complete image in the Prop's limited RAM first.

As to compression, LZW-GIF is probably the best candidate for crisp graphic images (as opposed to photos), since it's lossless. However, it does require a large chunk of memory for its string table, so I don't know how viable it is for the Prop.

-Phil

Phil Pilgrim (PhiPi)

I've updated the object in the top post. Now the grid lines scroll with the plot, and you can choose to add minor grid lines:



The Spinneret has been moved out to my shop, which has forced-air electric heat. You can see when the heater comes on. BTW, it's not really that hot in here. (I'm not that old!) The ambient near the temp sensor is about 10 degrees warmer than the overall air temperature. The W5100 puts out a bit of heat; the Prop, not so much.

-Phil