I admit it: I'm a total geek. I love electronics, programming, 3D art, vintage Apple hardware, and whisky. I'm always juggling half a dozen projects. I also enjoy documenting it all: my successes, my failures, my experiences... and everything geeky along the way.


 
 
 
 
 

E-Paper Clock Prototyping, Part II | Kevin Rye.net - Main

Kevin Rye

Geek Extraordinaire. Yeh, I said it.

E-Paper Clock Prototyping, Part II

I left off with my last E-Paper clock post saying that I was waiting for a new display to arrive from SparkFun. The one I received has some bad segments. I contacted SparkFun’s Customer Service Dept. and sent them a picture of the wonky segments. They sent me a new one right away, and threw in a new breakout board for kicks! Gotta love those guys.

new epaper display

As far as the code, I was having some trouble formatting the strings for the time and date. I gave up on that since this display does a pretty bad job of handing them. It kept padding them with zeros. Depending on the contents of the array sent compared to the buffer size of the array, I’d get a bunch of weird characters at the end of the strings, or all zeroes. Rather than drive myself mad, I shelved it for a week until the new display arrived.

While I waited for a new display, I posted a question over at the Arduino forums about the string issue I was having. Someone suggested dumping the strings in favor of the sprintf() command. Done.

I redid my code and it worked like a charm.

  char timeChr[10];
  sprintf(timeChr, "%s%d%s%d%s", space, hours, seperator, minutes, suffix);

  char dateChr[10];
  sprintf(dateChr, " %s %dz%d ", dayOfWeekChar, month, dayOfMonth);

  epaper.writeTop(timeChr);
  epaper.writeBottom(dateChr);
  epaper.writeDisplay();

A dash and a slash aren’t standard characters for the library. I had to define my own.

In the e-paper library, I added the following lines:

char dashChar[16] = {0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0};
char slashChar[16] = {0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0};

And in the “createData” function:

case '/':
        for (int j=0; j<16; j++)
          characterData[(9-i)*16 + j] = slashChar[j];
        break;
case '-':
        for (int j=0; j<16; j++)
          characterData[(9-i)*16 + j] = dashChar[j];
        break;

You can easily generate your own digits using this cool little e-paper character app. (There’s a link to the app in the comments over at SparkFun.)

epaper pattern ap
I also changed the 5’s and S’s. I didn’t like they way they looked.

5s and Ss

Here’s the final results:

new epaper display with finished code 2

I’m so glad I got rid of the weirdness at the end of the strings. That was really holding me up.

new-epaper-display-with-finished-code-1

Yeh progress!

I’ve held off for now on writing code to set the time and date until I can decide on the hardware. I might forgo the use of 3 individual buttons like I used on the LCD clock. I might use a joystick or a 3-way navigation switch. I’ll have to see how much real estate I have once I start laying out parts in Eagle.

See this project from start to finish:
E-Paper Display
E-Paper Clock Prototyping, Part I
E-Paper Clock Prototyping, Part II
E-Paper Clock Prototyping, Part III
E-Paper Clock Final Assembly