Roo Reynolds - What’s Next?

Microprinter Sparklines

Posted by Roo - 18/07/09 at 10:07:28 am

Ever since Tom Taylor inspired quite a few of us to play with printers, I’ve been seeing what I can get mine to do. So far: barcodes were pretty quick. More recently, daily digests, twitter updates and even printing an entire a book. What’s next?

Sparklines turned out to be fairly easy. I’ve written a basic Java library for talking to the printer, which I’ve shared on Github. The latest version of Microprinter.java connects over USB to the microprinter_sketch.pde Arduino sketch which then simply relays whatever you send to it on to the printer.

The Java library contains a method called printSparkline(), which takes a label and an array of data. Here’s how you’d use it to create the printout shown above:

int[] sawBytes = new int[256];
int current = 0;
boolean flip = true;
for (int i = 0; i < 256; i++) {
   if ((current >= 7 && flip) || (current <= 0 && !flip)) flip = ! flip;
if (flip) {
   current++;
} else {
   current--;
}
   sawBytes[i] = current;
}
microprinter.printSparkline("saw............", sawBytes);

int[] sineArray = new int[256];
for (float i = 0; i < 256; i++) {
   sineArray[(int) i] = (int) (Math.sin(i / 5) * 1000);
}
microprinter.printSparkline("sin............", sineArray);

Please feel free to adapt and improve. If you make any serious changes I'd love to see them, and don't forget to get involved on the microprinter wiki.