{"id":384,"date":"2012-01-11T17:13:15","date_gmt":"2012-01-11T22:13:15","guid":{"rendered":"http:\/\/www.jetmore.org\/john\/blog\/?p=384"},"modified":"2012-03-30T14:10:24","modified_gmt":"2012-03-30T18:10:24","slug":"more-character-display-abuse","status":"publish","type":"post","link":"https:\/\/www.jetmore.org\/john\/blog\/2012\/01\/more-character-display-abuse\/","title":{"rendered":"More Character Display Abuse"},"content":{"rendered":"

A few months ago I posted<\/a> about a project I was working on whose primary goal was to drive single-pixel drawing on a 16×2 character display. Of course the real goal of the project was just to move forward with electronics, trying new things in both software and hardware.<\/p>\n

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Where Were We?<\/h3>\n

When last we left the project, I had just realized that my plan to draw (persistent) pixels on the entire 16×2 display wouldn’t work with the LiquidCrystal library’s 8-custom-character limit. Here is a very abbreviated version of the 4 possible next-steps I set out for the project:<\/p>\n

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  1. Make the drawing grid 2×4 instead of 2×16, just to get the persistent drawing working. Add as much physical “bling” to the project as possible just to play with new stuff and multiple components updating in the loop.<\/li>\n
  2. Investigate overcoming the 8-custom-character limit inside the LiquidCrystal library.<\/li>\n
  3. If needed, investigate bypassing the LiquidCrystal library entirely to bypass the custom-character limit.<\/li>\n
  4. Investigate methods for circuit documentation, using this project as the guinea pig (emphasis on versionable files and multi-platform support)<\/li>\n<\/ol>\n
    <\/div>\n

    Goals 2 & 3: Getting More Than 8 Custom Chars<\/h3>\n

    The easiest thing to discuss is what didn’t work out. I never spent any time looking into #2 or #3, but a commentor<\/a> on the previous post left a link to an Arduino forum post<\/a> that implied that 8-custom-character limit is due to the hardware itself, not the library. That link, plus a little more googling, leads me to believe this isn’t a path worth walking down right now.<\/p>\n

     <\/p>\n

    Goal 1: Multi-Pixel Drawing<\/h3>\n

    I did decide that my itch for this project wouldn’t be properly scratched until I had persistent, multi-pixel drawing working. By this I mean that you have a cursor of one pixel, and anywhere you move that cursor lights up and stays lit (unlike the last version, where the pixel could travel anywhere, but they didn’t stay lit). I was able to get this implemented without too much pain. Actually, the vast majority of the time I spent on this was debugging a hardware issue outside of my control that I didn’t have enough experience to recognize at first (quicky blog post later on that).<\/p>\n

    Also while working on this I added a clear button to the circuit and some positioning debug information to the display.<\/p>\n